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2023RNAAS...7..216S | A Pipeline for Modeling Rapidly Rotating Stars | Recent stellar intensity interferometry observations of stars at 416 nm complement Michelson interferometry observations in the near-infrared where stellar surface intensity gradients (e.g., limb darkening) are weaker. Intensity gradients due to gravity darkening in rapidly rotating stars are also expected to show higher contrast at 416 nm relative to the near-infrared. We have created a software pipeline to model stellar photospheres of rapidly rotating stars to compare predictions at these wavelength regions. The pipeline can produce model images, visibility predictions, and synthetic spectra. Here we show examples for the Be star β CMi, which has not been interferometrically imaged. We see higher contrast from gravity darkening at 416 nm in model images for rapid rotators, but only for those stars that are not viewed equator-on. | [
1859,
1237,
932,
1629,
680
] | [
"astronomy data modeling",
"stellar photospheres",
"long baseline interferometry",
"stellar rotation",
"gravity darkening"
] |
2022ApJ...936...18D | The Great Dimming of Betelgeuse: A Surface Mass Ejection and Its Consequences | The bright supergiant, Betelgeuse (Alpha Orionis, HD 39801), underwent a historic optical dimming during 2020 January 27-February 13. Many imaging and spectroscopic observations across the electromagnetic spectrum were obtained prior to, during, and subsequent to this dimming event. These observations of Betelgeuse reveal that a substantial surface mass ejection (SME) occurred and moved out through the extended atmosphere of the supergiant. A photospheric shock occurred in 2019 January-March, progressed through the extended atmosphere of the star during the following 11 months and led to dust production in the atmosphere. Resulting from the substantial mass outflow, the stellar photosphere was left with lower temperatures and the chromosphere with a lower density. The mass ejected could represent a significant fraction of the total annual mass-loss rate from the star suggesting that episodic mass-loss events can contribute an amount comparable to that of the stellar wind. Following the SME, Betelgeuse was left with a cooler average photosphere, an unusual short photometric oscillation, reduced velocity excursions, and the disappearance of the ~400 day pulsation in the optical and radial velocity for more than two years following the Great Dimming. | [
988,
1375,
1613,
230,
1584
] | [
"m supergiant stars",
"red supergiant stars",
"stellar mass loss",
"stellar chromospheres",
"stellar atmospheres"
] |
2020AJ....159..143W | Supercatastrophic Disruption of Asteroids in the Context of SOHO Comet, Fireball, and Meteor Observations | Granvik et al. reported an absence of asteroids on orbits with perihelia near the Sun that they attribute to the "supercatastrophic disruption" of these bodies. Here we investigate whether there is evidence for this process among other bodies with similarly low perihelia: near-Earth asteroids, Solar and Heliospheric Observatory (SOHO) comets, and meter- and millimeter-sized meteoroids. We determine that no known near-Earth asteroids have past (last 10<SUP>4</SUP> yr) histories residing significantly inside the Granvik et al. limit, indirectly supporting the disruption hypothesis. The exception is asteroid (467372) 2004 LG, which spent 2500 yr within this limit and thus presents a challenge to that theory. Phaethon has a perihelion distance hovering just above the limit and may be undergoing slow disruption, which may be the source of its dust complex. We find that the rate at which ungrouped SOHO comets are observed is consistent with expected rates for the injection of small (25 m) class asteroids into the near-Sun region and suggest that this fraction of the SOHO-observed comet population may in fact be asteroidal in origin. We also find that there is an absence of meter-sized bodies with near-Sun perihelia but an excess of millimeter-sized meteoroids. This implies that if near-Sun asteroids disrupt, they do not simply fragment into meter-sized chunks but ultimately disintegrate into millimeter-sized particles. We propose that the disruption of near-Sun asteroids, as well as the anomalous brightening and destruction processes that affect SOHO comets, occur through meteoroid erosion, that is, the removal of material through impacts by high-speed near-Sun meteoroids. | [
1528,
1040,
1092,
280,
890,
72
] | [
"solar system",
"meteoroids",
"near-earth objects",
"comets",
"kreutz group",
"asteroids"
] |
2021ApJ...921L..26Z | White-light Continuum Observation of the Off-limb Loops of the SOL2017-09-10 X8.2 Flare: Temporal and Spatial Variations | Observations of the Sun's off-limb white-light (WL) flares offer rare opportunities to study the energy release and transport mechanisms in flare loops. One of the best such events was SOL2017-09-10, an X8.2 flare that occurred near the Sun's west limb on 2017 September 10 and produced a WL loop system lasting more than 60 minutes and reaching an altitude higher than 30 Mm. The event was well observed by a suite of ground- and space-based instruments, including the Solar Dynamics Observatory/Helioseismic and Magnetic Imager (SDO/HMI) that captured its off-limb loops in WL continuum near Fe I 6173 Å, and the Atmospheric Imager Assembly (SDO/AIA) that observed its ultraviolet (UV) and extreme-ultraviolet (EUV) counterparts. We found quasi-periodic pulsations in the WL and UV emissions at the flare loop-top with a period around 8.0 minutes. Each pulsation appears to have an EUV counterpart that occurs earlier in time and higher in altitude. Despite many similarities in the WL and UV images and light curves, the WL flux at the loop-top continues to grow for about 16 minutes while the UV fluxes gradually decay. We discuss the implication of these unprecedented observations on the understanding of the enigmatic off-limb WL flare emission mechanisms. | [
1475,
1983,
1988,
1515
] | [
"solar activity",
"solar white-light flares",
"active solar corona",
"solar oscillations"
] |
2021PSJ.....2..117L | Spectrophotometric Modeling and Mapping of (101955) Bennu | Using hyperspectral data collected by OVIRS, the visible and infrared spectrometer on board the Origins, Spectral Interpretation, Resource Identification, and Security-Regolith Explorer (OSIRIS-REx) spacecraft, we modeled the global average spectrophotometric properties of the carbonaceous asteroid (101955) Bennu and mapped their variations. We restricted our analysis to 0.4-2.5 μm to avoid the wavelengths where thermal emission from the asteroid dominates (>2.5 μm). Bennu has global photometric properties typical of dark asteroids; we found a geometric albedo of 0.046 ± 0.007 and a linear phase slope of 0.024 ± 0.007 mag deg<SUP>-1</SUP> at 0.55 μm. The average spectral slope of Bennu's normal albedo is -0.0030 μm<SUP>-1</SUP>, and the phase-reddening parameter is 4.3 × 10<SUP>-4</SUP> μm<SUP>-1</SUP> deg<SUP>-1</SUP>, both over the spectral range of 0.5-2.0 μm. We produced normal albedo maps and phase slope maps at all spectral channels, from which we derived spectral slope and phase-reddening maps. Correlation analysis suggests that phase slope variations on Bennu are likely due to photometric roughness variation. A correlation between photometric and thermal roughness is evident, implying that the roughness of Bennu is self-similar on scales from tens of microns to meters. Our analysis reveals latitudinal trends in the spectral color slope and phase reddening on Bennu. The equatorial region appears to be redder than the global average, and the spectral slope decreases toward higher latitudes. Phase reddening on Bennu is relatively weak in the equatorial region and shows an asymmetry between the northern and southern hemispheres. We attributed the latitudinal trend to the geophysical conditions on Bennu that result in a global pattern of mass flow toward the equator. | [
1670,
1858,
1092
] | [
"surface photometry",
"astronomy data analysis",
"near-earth objects"
] |
2021ApJ...911...83D | Optimal Softening for Gravitational Force Calculations in N-body Dynamics | The choice of the optimal value of the softening length (ɛ<SUB>i</SUB>) of each particle dealing with N-body simulations has a profound impact on error values in the gravitational force calculation. A slight deviation from its exact optimal value may result in a large error in the calculation. In this paper we augment the accuracy of the existing gravitational force calculation methods by providing a new technique to calculate the individual optimal values of ɛ<SUB>i</SUB> for various configurations of the Plummer density model. We have proposed an expression ${\epsilon }_{\lambda ,i}={\lambda }_{i}{\left(\tfrac{{m}_{i}}{{\rho }_{i}}\right)}^{\tfrac{1}{3}}$ that relates each particle by considering the average characteristic length (λ<SUB>i</SUB>) and density (ρ<SUB>i</SUB>), unlike previous studies that considered ɛ<SUB>i</SUB> as an exclusive function of ρ<SUB>i</SUB>. We have performed gravitational force calculations for each and every particle from the Plummer density model using compact as well as noncompact gravitational force methods based on smoothed particle hydrodynamics. We have tested our new equation for the entire range of numerical simulations performed during the study. It is found that the errors in our force calculations are not only lower than those estimated from previous studies but also remain flat for various considerations of nearest neighboring particles (N<SUB>neigh</SUB>). The adjusted expression of ɛ<SUB>λ,i</SUB> in our study has less dependence on N<SUB>neigh</SUB> in the Plummer sphere. Finally, based on the results obtained using the method proposed in this study, we find that it remarkably improves both the accuracy as well as the stability of the gravitational force calculation. | [
1110,
767,
101,
1082
] | [
"newtonian gravitation",
"hydrodynamical simulations",
"astrophysical fluid dynamics",
"n-body problem"
] |
2020AJ....160...44L | Refining the Census of the Upper Scorpius Association with Gaia | We have refined the census of stars and brown dwarfs in the Upper Sco association (∼10 Myr, ∼145 pc) by (1) updating the selection of candidate members from our previous survey to include the high-precision astrometry from the second data release of Gaia, (2) obtaining spectra of a few hundred candidate members to measure their spectral types and verify their youth, and (3) assessing the membership (largely with Gaia astrometry) of 2020 stars toward Upper Sco that show evidence of youth in this work and previous studies. We arrive at a catalog of 1761 objects that are adopted as members of Upper Sco. The distribution of spectral types among the adopted members is similar to those in other nearby star-forming regions, indicating a similar initial mass function. In previous studies, we have compiled mid-infrared photometry from the Wide-field Infrared Survey Explorer and the Spitzer Space Telescope for members of Upper Sco and used those data to identify the stars that show evidence of circumstellar disks; we present the same analysis for our new catalog of members. As in earlier work, we find that the fraction of members with disks increases with lower stellar masses, ranging from ≲10% for >1 M<SUB>⊙</SUB> to ∼22% for 0.01-0.3 M<SUB>⊙</SUB>. Finally, we have estimated the relative ages of Upper Sco and other young associations using their sequences of low-mass stars in ${M}_{{G}_{\mathrm{RP}}}$ versus G<SUB>BP</SUB> - G<SUB>RP</SUB>. This comparison indicates that Upper Sco is a factor of two younger than the β Pic association (21-24 Myr) according to both nonmagnetic and magnetic evolutionary models. <SUP>*</SUP> Based on observations made with the Two Micron All Sky Survey, the Gaia mission, the NASA Infrared Telescope Facility, Cerro Tololo Inter-American Observatory, Gemini Observatory, the Magellan Baade Telescope at Las Campanas Observatory, and the Bok Reflector at Steward Observatory. | [
185,
1300,
1140,
1569,
235,
796,
1582,
2050
] | [
"brown dwarfs",
"protoplanetary disks",
"ob associations",
"star formation",
"circumstellar disks",
"initial mass function",
"stellar associations",
"low mass stars"
] |
2021AJ....162..167F | TOI-1749: an M dwarf with a Trio of Planets including a Near-resonant Pair | We report the discovery of one super-Earth- (TOI-1749b) and two sub-Neptune-sized planets (TOI-1749c and TOI-1749d) transiting an early M dwarf at a distance of 100 pc, which were first identified as planetary candidates using data from the TESS photometric survey. We have followed up this system from the ground by means of multiband transit photometry, adaptive optics imaging, and low-resolution spectroscopy, from which we have validated the planetary nature of the candidates. We find that TOI-1749b, c, and d have orbital periods of 2.39, 4.49, and 9.05 days, and radii of 1.4, 2.1, and 2.5 R<SUB>⊕</SUB>, respectively. We also place 95% confidence upper limits on the masses of 57, 14, and 15 M<SUB>⊕</SUB> for TOI-1749b, c, and d, respectively, from transit timing variations. The periods, sizes, and tentative masses of these planets are in line with a scenario in which all three planets initially had a hydrogen envelope on top of a rocky core, and only the envelope of the innermost planet has been stripped away by photoevaporation and/or core-powered mass-loss mechanisms. These planets are similar to other planetary trios found around M dwarfs, such as TOI-175b,c,d and TOI-270b,c,d, in the sense that the outer pair has a period ratio within 1% of 2. Such a characteristic orbital configuration, in which an additional planet is located interior to a near 2:1 period-ratio pair, is relatively rare around FGK dwarfs. | [
1711,
489,
1707,
1655,
1063,
982
] | [
"transits",
"exoplanet detection methods",
"transit duration variation method",
"super earths",
"mini neptunes",
"m dwarf stars"
] |
2021ApJ...908...66P | The First Extensive Exploration of UV-bright Stars in the Globular Cluster NGC 2808 | In this study, we identified and characterized the hot and luminous UV-bright stars in the globular cluster NGC 2808. We combined data from the Ultra Violet Imaging Telescope (UVIT) on board the Indian space satellite AstroSat with the Hubble Space Telescope UV Globular Cluster Survey data for the central region (within $\sim 2\buildrel{\,\prime}\over{.} 7\times 2\buildrel{\,\prime}\over{.} 7$ ) and Gaia and ground-based optical photometry for the outer parts of the cluster. We constructed the UV and UV-optical color-magnitude diagrams, compared the horizontal branch (HB) members with the theoretical zero- and terminal-age HB models, and identified 34 UV-bright stars. The spectral energy distributions of the UV-bright stars were fitted with theoretical models to estimate their effective temperatures (12,500-100,000 K), radii (0.13-2.2 R<SUB>⊙</SUB>), and luminosities (∼40-3000 L<SUB>⊙</SUB>) for the first time. These stars were then placed on the Hertzsprung-Russell diagram, along with theoretical post-HB evolutionary tracks, to assess their evolutionary status. The models suggest that most of these stars are in the asymptotic giant branch (AGB)-manqué phase, and all except three have evolutionary masses <0.53 M<SUB>⊙</SUB>. We also calculated the theoretically expected number of hot post-(early)-AGB stars in this cluster and found the range to match our observations. Seven UV-bright stars located in the outer region of the cluster, identified from the AstroSat/UVIT images, are ideal candidates for detailed follow-up spectroscopic studies. | [
656,
2121,
1740,
725,
746
] | [
"globular star clusters",
"post-asymptotic giant branch stars",
"ultraviolet photometry",
"hertzsprung russell diagram",
"horizontal branch stars"
] |
2021ApJ...914..119Y | A Bayesian ILC Method for CMB B-mode Posterior Estimation and Reconstruction of Primordial Gravity Wave Signal | The cosmic microwave background (CMB) radiation B-mode polarization signal contains the unique signature of primordial metric perturbations produced during the inflation. The separation of the weak CMB B-mode signal from strong foreground contamination in observed maps is a complex task, and proposed new-generation low-noise satellite missions compete with the weak signal level of this gravitational background. In this paper, for the first time, we employ a foreground model-independent internal linear combination (ILC) method to reconstruct the CMB B-mode signal using simulated observations over large angular scales of the sky of six frequency bands of the future-generation CMB mission Probe of Inflation and Cosmic Origins (PICO). We estimate the joint CMB B-mode posterior density following the interleaving Gibbs steps of the B-mode angular power spectrum and cleaned map samples using the ILC method. We extend and improve the earlier reported Bayesian ILC method to analyze weak CMB B-mode reconstruction by introducing noise-bias corrections at two stages during the ILC weight estimation. By performing 200 Monte Carlo simulations of the Bayesian ILC method, we find that our method can reconstruct the CMB signals and the joint posterior density accurately over large angular scales of the sky. We estimate the Blackwell-Rao statistics of the marginal density of the CMB B-mode angular power spectrum and use them to estimate the joint density of the tensor-to-scalar ratio r and a lensing power spectrum amplitude ${A}^{{\rm{lens}}}$ . Using 200 Monte Carlo simulations of the delensing approach, we find that our method can achieve an unbiased detection of the primordial gravitational-wave signal r with more than 8σ significance for levels of $r\geqslant 0.01$ for input frequency maps with realistic lensing and foregrounds with constant spectral indices. | [
322,
506,
319,
1944
] | [
"cosmic microwave background radiation",
"extragalactic astronomy",
"cosmic inflation",
"principal component analysis"
] |
2022AJ....163..274P | Colors of Irregular Satellites of Saturn with the Dark Energy Camera | We report g - r and r - i new colors for 21 Saturn Irregular Satellites; among them, four previously unreported. This is the highest number of Saturn Irregular satellites reported in a single survey. These satellites were measured by "stacking" their observations to increase their signal without trailing. This work describes a novel processing algorithm that enables the detection of faint sources under significant background noise and in front of a severely crowded field. Our survey shows these new color measurements of Saturn Irregular Satellites are consistent with other Irregular Satellites populations as found in previous works and reinforcing the observation that the lack of ultrared objects among the irregular satellites is a real feature that separates them from the trans-Neptunian objects (their posited source population). | [
1077,
2027,
1427,
1684
] | [
"multi-color photometry",
"irregular satellites",
"saturnian satellites",
"astronomical techniques"
] |
2023PSJ.....4..118V | Titan's North-South Haze Asymmetry Ratio and Boundary at Visible Wavelengths over the Cassini Mission | We document the evolution of the north-south asymmetry (NSA) of Titan's haze albedo during the Cassini mission between 2004 and 2017. We analyze coadded cube images taken at 96 distinct wavelengths between 0.35 and 1.05 μm by the Cassini Visual and Infrared Mapping Spectrometer (VIMS-V) instrument from 14 Titan flybys. Over half of a Titan year, we observe a near-complete transition in the NSA boundary latitude across the geographic equator from the southern to the northern hemisphere, including a 3 yr fading of the boundary for several years after the equinox. The fading transition of the NSA matches previous observations of a reversal of the NSA in Hubble Space Telescope images of Titan before the winter solstice between 1997 and 2000. A comparison of NSA images taken at similar times but different phase angles shows the NSA boundary is detectable, albeit with less contrast, at moderately high phase angles (~90°). Analysis of the NSA boundary in T61 and T67 VIMS images further supports a small tilt between the superrotating atmosphere and the solid body of Titan, as suggested in a previous analysis of 0.890 μm images from the Cassini Imaging Science Subsystem. | [
1859,
2306,
2186,
2301,
2300,
2321,
293
] | [
"astronomy data modeling",
"astronomy image processing",
"titan",
"atmospheric evolution",
"atmospheric dynamics",
"albedo",
"computational astronomy"
] |
2020ApJ...896..111G | A Second-order Moment of Microlensing Variability as a Novel Tool to Constrain Source Emission Size or Discrete Lens Demographics in Extragalactic Research | We define a second-order moment of the observational differential microlensing curves that can be used to impose constraints on physical properties of lensed quasars. We show that this quantity is sensitive both to variations in the source size and the deflector mass. We formulize a methodology to recover the source size from the observational measurements when the mass spectrum is fixed. As a case study, we test it with a sample of four quadruple lenses, both in simulated scenarios and with real data from the Chandra X-ray Observatory. In our simulations with a uniform stellar population the method works best to detect sources around 0.1 Einstein radii, giving correct upper/lower limits for much smaller/bigger sizes without requiring a big leap in additional computational effort as compared to a single-epoch approach, yet taking advantage of multi-epoch information. We apply the method to a small sample of X-ray data from four objects assuming a range of star masses, and obtain a degeneracy relation between the source size and deflector mass. Combined with previous estimates for the size of the X-ray corona, the degeneracy relation suggests that X-ray microlensing is mainly induced by planetary mass objects. | [
14,
159,
670,
1318,
1319
] | [
"accretion",
"black hole physics",
"gravitational lensing",
"quasar microlensing",
"quasars"
] |
2020PSJ.....1...35H | Tidal Currents Detected in Kraken Mare Straits from Cassini VIMS Sun Glitter Observations | We present Cassini Visual and Infrared Mapping Spectrometer (VIMS) observations of sun glitter—wave-induced reflections from a liquid surface offset from a specular point—on Kraken Mare. sun glitter reveals rough sea surfaces around Kraken Mare, namely the coasts and narrow straits. The sun glitter observations indicate wave activity driven by the winds and tidal currents in Kraken Mare during northern summer. T104 Cassini VIMS observations show three sun glitter features in Bayta Fretum indicative of variegated wave fields. We cannot uniquely determine one source for the coastal Bayta waves, but we lean toward the interpretation of surface winds, because tidal currents should be too weak to generate capillary-gravity waves in Bayta Fretum. T105 and T110 observations reveal wave fields in the straits of Seldon Fretum, Lulworth Sinus, and Tunu Sinus that likely originate from the constriction of tidal currents. Coastlines of Bermoothes and Hufaidh Insulae adjoin rough sea surfaces, suggesting a complex interplay of wind-roughened seas and localized tidal currents. Bermoothes and Hufaidh Insulae may share characteristics of either the Torres Strait off Australia or the Åland region of Finland, summarized as an island-dense strait with shallow bathymetry that hosts complex surface circulation patterns. Hufaidh Insulae could host seafloor bedforms formed by tidal currents with an abundant sediment supply, similar to the Torres Strait. The coastlines of Hufaidh and Bermoothes Insulae likely host ria or flooded coastal inlets, suggesting that the Insulae may be local peaks of primordial crust isolated by an episode of sea-level rise or tectonic uplift. | [
1427,
1150
] | [
"saturnian satellites",
"ocean-atmosphere interactions"
] |
2023AJ....166..139M | Speckle Interferometry at SOAR in 2022 | Results of the speckle-interferometry observations at the 4.1 m SOuthern Astrophysical Research Telescope obtained during 2022 are presented: 2508 measurements of 1925 resolved pairs or subsystems and 785 nonresolutions of 611 targets; 26 pairs are resolved here for the first time. This work continues our long-term effort to monitor orbital motion in close binaries and hierarchical systems. A large number of orbits have been updated using these measurements. | [
806
] | [
"interferometric binary stars"
] |
2023AJ....166..130S | Orbital Alignment of the Eccentric Warm Jupiter TOI-677 b | Warm Jupiters lay out an excellent laboratory for testing models of planet formation and migration. Their separation from the host star makes tidal reprocessing of their orbits ineffective, which preserves the orbital architectures that result from the planet-forming process. Among the measurable properties, the orbital inclination with respect to the stellar rotational axis, stands out as a crucial diagnostic for understanding the migration mechanisms behind the origin of close-in planets. Observational limitations have made the procurement of spin-orbit measurements heavily biased toward hot Jupiter systems. In recent years, however, high-precision spectroscopy has begun to provide obliquity measurements for planets well into the warm Jupiter regime. In this study, we present Rossiter-McLaughlin (RM) measurements of the projected obliquity angle for the warm Jupiter TOI-677 b using ESPRESSO at the VLT. TOI-677 b exhibits an extreme degree of alignment (λ = 0.3 ± 1.3 deg), which is particularly puzzling given its significant eccentricity (e ≈ 0.45). TOI-677 b thus joins a growing class of close-in giants that exhibit large eccentricities and low spin-orbit angles, which is a configuration not predicted by existing models. We also present the detection of a candidate outer brown dwarf companion on an eccentric, wide orbit (e ≈ 0.4 and P ≈ 13 yr). Using simple estimates, we show that this companion is unlikely to be the cause of the unusual orbit of TOI-677 b. Therefore, it is essential that future efforts prioritize the acquisition of RM measurements for warm Jupiters. | [
498,
1243,
490,
2205,
1332,
1711
] | [
"exoplanets",
"planetary alignment",
"exoplanet dynamics",
"exoplanet migration",
"radial velocity",
"transits"
] |
2023ApJ...943..144M | Principal-component Interferometric Modeling (PRIMO), an Algorithm for EHT Data. I. Reconstructing Images from Simulated EHT Observations | The sparse interferometric coverage of the Event Horizon Telescope (EHT) poses a significant challenge for both reconstruction and model fitting of black hole images. PRIMO is a new principal components analysis-based algorithm for image reconstruction that uses the results of high-fidelity general relativistic, magnetohydrodynamic simulations of low-luminosity accretion flows as a training set. This allows the reconstruction of images that are consistent with the interferometric data and that live in the space of images that is spanned by the simulations. PRIMO follows Monte Carlo Markov Chains to fit a linear combination of principal components derived from an ensemble of simulated images to interferometric data. We show that PRIMO can efficiently and accurately reconstruct synthetic EHT data sets for several simulated images, even when the simulation parameters are significantly different from those of the image ensemble that was used to generate the principal components. The resulting reconstructions achieve resolution that is consistent with the performance of the array and do not introduce significant biases in image features such as the diameter of the ring of emission. | [
1769,
159,
2306,
808,
1944,
14
] | [
"very long baseline interferometry",
"black hole physics",
"astronomy image processing",
"interferometry",
"principal component analysis",
"accretion"
] |
2021AJ....161...21C | Identifying Bound Stellar Companions to Kepler Exoplanet Host Stars Using Speckle Imaging | The Kepler mission and subsequent ground-based follow-up observations have revealed a number of exoplanet host stars with nearby stellar companions. This study presents speckle observations of 57 Kepler objects of interest (KOIs) that are also double stars, each observed over a 3-8 yr period, which has allowed us to track their relative motions with high precision. Measuring the position angle and separation of the companion with respect to the primary can help determine if the pair exhibits common proper motion, indicating it is likely to be a bound binary system. We report on the motions of 34 KOIs that have close stellar companions, three of which are triple stars, for a total of 37 companions studied. Eighteen of the 34 systems are confirmed exoplanet hosts, including one triple star, while four other systems have been subsequently judged to be false positives and twelve are yet to be confirmed as planet hosts. We find that 21 are most likely to be common proper motion pairs, 4 are line-of-sight companions, and 12 are of an uncertain disposition at present. The fraction of the confirmed exoplanet host systems that are common proper motion pairs is approximately 86% in this sample. In this subsample, the planets are exclusively found with periods of less than 110 days, so that in all cases the stellar companion is found at a much larger separation from the planet host star than the planet itself. A preliminary period-radius relation for the confirmed planets in our sample suggests no obvious differences at this stage with the full sample of known exoplanets. | [
1777,
806,
1242,
1552,
80
] | [
"visual binary stars",
"interferometric binary stars",
"planet hosting stars",
"speckle interferometry",
"astrometry"
] |
2024PASP..136c3001C | TONGS: A Treasury of Nearby Galaxy Surveys | The beginning of the 21st century marked the "modern era of galaxy surveys" in astronomy. Rapid innovation in observing technology, combined with the base built by galaxy catalogs and atlases dating back centuries, sparked an explosion of new observational programs driven by efforts to understand the different processes driving galaxy evolution. This review aims to answer the following science questions: (1) how have galaxy surveys evolved in the past 20 yr, and how have traditional observational programs been affected by the rise of large panoramic surveys, (2) can the term "nearby" be quantified in the context of galaxy surveys, and (3) how complete is the coverage of the nearby universe and what areas hold the largest opportunity for future work? We define a galaxy survey as a systematically obtained data set which aims to characterize a set of astronomical objects. Galaxy surveys can further be subdivided based on the methods used to select the objects to observe, the properties of the survey samples (e.g., distance or morphology), or the observing strategies used. We focus on pointed nearby galaxy surveys, which we define as surveys which observe a specific sample of target galaxies. Through a study of 43 nearby galaxy surveys, we find no standardized quantitative definition for "nearby" with surveys covering a wide range of distances. We observe that since 2003, traditional targeted galaxy surveys have undergone a dramatic evolution, transitioning from large, statistical surveys to small, ultra-specific projects which compliment the rise of large high resolution panoramic surveys. While wavelength regimes observable from the ground (such as radio or optical wavelengths) host numerous surveys, the largest opportunity for future work is within the less covered space-based wavelength regimes (especially ultraviolet and X-ray). | [
1868,
573,
611,
2171,
212,
590
] | [
"history of astronomy",
"galaxies",
"galaxy photometry",
"galaxy spectroscopy",
"celestial objects catalogs",
"galaxy distances"
] |
2020ApJ...902L..44C | Neon Cluster Formation and Phase Separation during White Dwarf Cooling | Recent observations of Galactic white dwarfs (WDs) with Gaia suggest there is a population of massive crystallizing WDs exhibiting anomalous cooling—the Q branch. While single-particle <SUP>22</SUP>Ne sedimentation has long been considered a possible heat source, recent work suggests that <SUP>22</SUP>Ne must separate into clusters, enhancing diffusion, in order for sedimentation to provide heating on the observed timescale. We show definitively that <SUP>22</SUP>Ne cannot separate to form clusters in C/O WDs using molecular dynamics simulations, and we further present a general C/O/Ne phase diagram showing that strong <SUP>22</SUP>Ne enrichment is not achievable for <SUP>22</SUP>Ne abundance ≲30%. We conclude that the anomalous heating cannot be due to <SUP>22</SUP>Ne cluster sedimentation and that Q branch WDs may have an unusual composition, possibly rich with heavier elements. | [
1606,
367,
1083
] | [
"stellar interiors",
"degenerate matter",
"n-body simulations"
] |
2020AJ....160..170M | Mathematical Underpinnings of the Multiwavelength Structure of the Tip of the Red Giant Branch | We consider the application of the tip of the red giant branch (TRGB) in the optical and in the near-infrared for the determination of distances to nearby galaxies. We analyze ACS VI (F555W and F814W) data and self-consistently cross-calibrate WFC3-IR JH (F110W and F120W) data using an absolute magnitude calibration of M<SUB>I</SUB> = -4.05 mag as determined in the Large Magellanic Cloud using detached eclipsing binary star geometric parallaxes. We demonstrate how the optical and near-infrared calibrations of the TRGB method are mathematically self-consistent, and illustrate the mathematical basis and relations among these multiwavelength calibrations. We go on to present a method for determining the reddening, extinction, and the true modulus to the host galaxy using multiwavelength data. The power of the method is that with high-precision data, the reddening can be determined using the TRGB stars themselves, and decreases the systematic (albeit generally small) uncertainty in distance due to reddening for these halo stars. | [
1368,
1371,
394,
1595
] | [
"red giant branch",
"red giant tip",
"distance indicators",
"stellar distance"
] |
2020ApJ...892L..15Z | Periodic Fast Radio Bursts with Neutron Star Free Precession | The CHIME/FRB collaboration recently reported the detection of a 16 day periodicity in the arrival times of radio bursts from FRB 180916.J0158+65. We study the possibility that the observed periodicity arises from free precession of a magnetized neutron star, and put constraints on different components of the star's magnetic fields. Using a simple geometric model, where radio bursts are emitted from a rotating neutron star magnetosphere, we show that the emission pattern as a function of time can match that observed from FRB 180916.J0158+65. | [
289,
998,
1339,
1108,
992
] | [
"compact radiation sources",
"magnetospheric radio emissions",
"radio bursts",
"neutron stars",
"magnetars"
] |
2023ApJ...945...61N | A Superflare on YZ Canis Minoris Observed by the Seimei Telescope and TESS: Red Asymmetry of Hα Emission Associated with White-light Emission | Active M-type stars are known to often produce superflares on the surface. Radiation from stellar (super)flares is important for exoplanet habitability, but the mechanisms are not well understood. In this paper, we report simultaneous optical spectroscopic and photometric observations of a stellar superflare on an active M dwarf, YZ Canis Minoris, with the 3.8 m Seimei telescope and the Transiting Exoplanet Survey Satellite. The flare bolometric energy is ${1.3}_{-0.6}^{+1.6}\times {10}^{34}\,\mathrm{erg}$ and the Hα energy is ${3.0}_{-0.1}^{+0.1}\times {10}^{32}\,\mathrm{erg}$ . The Hα emission line profile shows red asymmetry throughout the flare, with a duration of 4.6-5.1 hr. The velocity of the red asymmetry is ~200-500 km s<SUP>-1</SUP> and the line width of Hα broadens up to 34 ± 14 Å. The redshifted velocity and line width of Hα line decay more rapidly than the equivalent width, and their time evolutions are correlated with that of the white-light emission. This indicates the possibility of the white light, the Hα red asymmetry, and the Hα line broadening originating from nearly the same site, i.e., the dense chromospheric condensation region, heated by nonthermal electrons. On the other hand, the flux ratio of the redshifted excess components to the central components is enhanced one hr after the flare's onset. This may be due to the main source of the red asymmetry changing to post-flare loops in the later phase of the flare. | [
1603,
1619,
1166,
1496,
996,
982,
1504,
1503,
994
] | [
"stellar flares",
"stellar phenomena",
"optical flares",
"solar flares",
"magnetic variable stars",
"m dwarf stars",
"solar magnetic reconnection",
"solar magnetic fields",
"magnetic fields"
] |
2024ApJ...962....9S | Disruption of Dark Matter Minihalos in the Milky Way Environment: Implications for Axion Miniclusters and Early Matter Domination | Many theories of dark matter beyond the weakly interacting massive particles paradigm feature an enhanced matter power spectrum on subparsec scales, leading to the formation of dense dark matter minihalos. Future local observations are promising to search for and constrain such substructures. The survival probability of these dense minihalos in the Milky Way environment is crucial for interpreting local observations. In this work, we investigate two environmental effects: stellar disruption and (smooth) tidal disruption. These two mechanisms are studied using semianalytic models and idealized N-body simulations. For stellar disruption, we perform a series of N-body simulations of isolated minihalo–star encounters to test and calibrate analytic models of stellar encounters before applying the model to the realistic Milky Way disk environment. For tidal disruption, we perform N-body simulations to confirm the effectiveness of the analytic treatment. Finally, we propose a framework to combine the hierarchical assembly and infall of minihalos to the Milky Way with the late-time disruption mechanisms. We make predictions for the mass functions of minihalos in the Milky Way. The mass survival fraction (at M <SUB>mh</SUB> ≥ 10<SUP>‑12</SUP> M <SUB>⊙</SUB>) of dense dark matter minihalos, e.g., for axion miniclusters and minihalos from early matter domination, is ∼60% with the relatively low-mass, compact population surviving. The survival fraction is insensitive to the detailed model parameters. We discuss various implications of the framework and future direct detection prospects. | [
353,
343,
1083,
1509,
664
] | [
"dark matter",
"cosmology",
"n-body simulations",
"solar neighborhood",
"gravitational disruption"
] |
2021ApJ...914....8M | Could Switchbacks Originate in the Lower Solar Atmosphere? II. Propagation of Switchbacks in the Solar Corona | The magnetic switchbacks observed recently by the Parker Solar Probe have raised the question about their nature and origin. One of the competing theories of their origin is the interchange reconnection in the solar corona. In this scenario, switchbacks are generated at the reconnection site between open and closed magnetic fields, and are either advected by an upflow or propagate as waves into the solar wind. In this paper we test the wave hypothesis, numerically modeling the propagation of a switchback, modeled as an embedded Alfvén wave packet of constant magnetic field magnitude, through the gravitationally stratified solar corona with different degrees of background magnetic field expansion. While switchbacks propagating in a uniform medium with no gravity are relatively stable, as reported previously, we find that gravitational stratification together with the expansion of the magnetic field act in multiple ways to deform the switchbacks. These include WKB effects, which depend on the degree of magnetic field expansion, and also finite-amplitude effects, such as the symmetry breaking between nonlinear advection and the Lorentz force. In a straight or radially expanding magnetic field the propagating switchbacks unfold into waves that cause minimal magnetic field deflections, while a super-radially expanding magnetic field aids in maintaining strong deflections. Other important effects are the mass uplift the propagating switchbacks induce and the reconnection and drainage of plasmoids contained within the switchbacks. In the Appendix, we examine a series of setups with different switchback configurations and parameters, which broaden the scope of our study. | [
1534,
1964,
23,
1995,
1948
] | [
"solar wind",
"magnetohydrodynamics",
"alfven waves",
"solar coronal waves",
"nonlinear regression"
] |
2021AJ....162....4N | Analysis of Hybrid Gas-Dust Outbursts Observed at 67P/Churyumov-Gerasimenko | Cometary outbursts offer a valuable window into the composition of comet nuclei with their forceful ejection of dust and volatiles in explosive events, revealing the interior components of the comet. Understanding how different types of outbursts influence the dust properties and volatile abundances, to better interpret what signatures can be attributed to primordial composition and what features are the result of processing, is an important task best undertaken with a multi-instrument approach. The European Space Agency Rosetta mission to 67P/Churyumov-Gerasimenko carried a suite of instruments capable of carrying out this task in the near-nucleus coma with unprecedented spatial and spectral resolution. In this work, we discuss two outbursts that occurred 2015 November 7 and were observed by three instruments on board: the Alice ultraviolet spectrograph, the Visual Infrared and Thermal Imaging Spectrometer, and the Optical, Spectroscopic, and Infrared Remote Imaging System. Together, the observations show that mixed gas and dust outbursts can have different spectral signatures representative of their initiating mechanisms, with the first outburst showing indicators of a cliff collapse origin and the second more representative of fresh volatiles being exposed via a deepening fracture. This analysis opens up the possibility of remote spectral classification of cometary outbursts with future work. | [
280,
1736,
1469,
2158
] | [
"comets",
"ultraviolet astronomy",
"small solar system bodies",
"neutral coma gases"
] |
2024ApJ...960...40G | Computed Rotational Collision Rate Coefficients for Recently Detected Anionic Cyanopolyynes | We report new results from quantum calculations of energy-transfer processes taking place in interstellar environments and involving two newly observed molecular species: C<SUB>5</SUB>N<SUP>-</SUP> and C<SUB>7</SUB>N<SUP>-</SUP> in collision with He atoms and p-H<SUB>2</SUB> molecules. These species are part of the anionic molecular chains labeled as cyanopolyynes, which have been observed over the years in molecule-rich circumstellar envelopes and in molecular clouds. In the present work, we first carry out new ab initio calculations for the C<SUB>7</SUB>N<SUP>-</SUP> interaction potential with He atoms and then obtain state-to-state rotationally inelastic cross sections and rate coefficients involving the same transitions, which have been observed experimentally by emission in the interstellar medium (ISM) from both of these linear species. For the C<SUB>5</SUB>N<SUP>-</SUP>/He system, we extend the calculations already published in Biwas et al. to compare more directly the two molecular anions. We extend further the quantum calculations by also computing in this work collision rate coefficients for the hydrogen molecule interacting with C<SUB>5</SUB>N<SUP>-</SUP>, using our previously computed interaction potential. Additionally, we obtain the same rate coefficients for the C<SUB>7</SUB>N<SUP>-</SUP>/H<SUB>2</SUB> system by using a scaling procedure that makes use of the new C<SUB>7</SUB>N<SUP>-</SUP>/He rate coefficients, as discussed in detail in the present paper. Their significance in affecting internal state populations in ISM environments where the anionic cyanopolyynes have been found is analyzed by using the concept of critical density indicators. Finally, similarities and differences between such species and the comparative efficiency of their collision rate coefficients are discussed. These new calculations suggest that, at least for the case of these longer chains, the rotational populations could reach local thermal equilibrium conditions within their observational environments. | [
2286
] | [
"collisional processes"
] |
2023RNAAS...7...18S | FluxCT: A Web Tool for Identifying Contaminating Flux in Kepler and TESS Target Pixel Files | We announce FluxCT, a web tool for identifying contaminating flux in Kepler and TESS target pixel files due to secondary visual sources. We demonstrate the usage of this tool and discuss the benefits of this tool over a simple Gaia radius search. FluxCT focuses on clarity and simplicity, where the only input needed from the user is a KIC or TIC ID. By more appropriately accounting for the actual shape of the photometric pixel apertures, FluxCT can produce much more accurate estimates of contaminating flux than simple radial cone searches. | [
1583,
1870,
1855
] | [
"stellar astronomy",
"educational software",
"astronomy software"
] |
2023ApJ...953...27L | The Fate of the Interstellar Medium in Early-type Galaxies. II. Observational Evidence for Morphological Quenching | The mechanism by which galaxies stop forming stars and get rid of their interstellar medium (ISM) remains elusive. Here, we study a sample of more than 2000 elliptical galaxies in which dust emission has been detected. This is the largest sample of such galaxies ever analyzed. We infer the timescale for removal of dust in these galaxies and investigate its dependence on physical and environmental properties. We obtain a dust-removal timescale in elliptical galaxies of τ = 2.26 ± 0.18 Gyr, corresponding to a half-life time of 1.57 ± 0.12 Gyr. This timescale does not depend on environment, stellar mass, or redshift. We observe a departure of dusty elliptical galaxies from the relation between star formation rate and dust mass. This is caused by the star formation rates declining faster than the dust masses and indicates that there exists an internal mechanism that affects star formation but leaves the ISM intact. Morphological quenching together with ionization or outflows caused by older stellar populations (Type Ia supernovae or planetary nebulae) is consistent with these observations. <SUP>*</SUP> Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA. | [
429,
456,
576,
594,
2040,
847,
2268
] | [
"early-type galaxies",
"elliptical galaxies",
"galaxy ages",
"galaxy evolution",
"galaxy quenching",
"interstellar medium",
"dust destruction"
] |
2020ApJ...905L..28B | Dark Sirens to Resolve the Hubble-Lemaître Tension | The planned sensitivity upgrades to the LIGO and Virgo facilities could uniquely identify host galaxies of dark sirens—compact binary coalescences without any electromagnetic counterparts—within a redshift of z = 0.1. This is aided by the higher-order spherical harmonic modes present in the gravitational-wave signal, which also improve distance estimation. In conjunction, sensitivity upgrades and higher modes will facilitate an accurate, independent measurement of the host galaxy's redshift in addition to the luminosity distance from the gravitational-wave observation to infer the Hubble-Lemaître constant H<SUB>0</SUB> to better than a few percent in 5 yr. A possible Voyager upgrade or third-generation facilities would further solidify the role of dark sirens for precision cosmology in the future. | [
343,
758,
763,
283,
675,
677,
676
] | [
"cosmology",
"hubble constant",
"hubble-lemaitre law",
"compact binary stars",
"gravitational wave astronomy",
"gravitational wave sources",
"gravitational wave detectors"
] |
2022ApJ...936..162S | NuSTAR Observations of AGNs with Low Observed X-Ray to [O III] Luminosity Ratios: Heavily Obscured AGNs or Turned-off AGNs? | Type 2 active galactic nuclei (AGNs) show signatures of accretion onto a supermassive black hole through strong, high-ionization, narrow emission lines extended on scales of hundreds to thousands of parsecs, but they lack the broad emission lines from close in to the black hole that characterize type 1 AGNs. The lack of broad emission could indicate obscuration of the innermost nuclear regions, or could indicate that the black hole is no longer strongly accreting. Since high-energy X-rays can penetrate thick obscuring columns, they have the power to distinguish these two scenarios. We present high-energy NuSTAR observations of nine Seyfert 2 AGNs from the Infrared Astronomical Satellite 12 μm survey, supplemented with low-energy X-ray observations from Chandra, XMM-Newton, and Swift. The galaxies were selected to have anomalously low observed 2-10 keV luminosities compared to their [O III] optical luminosities, a traditional diagnostic of heavily obscured AGNs, reaching into the Compton-thick regime for the highest hydrogen column densities (N <SUB>H</SUB> > 1.5 × 10<SUP>24</SUP> cm<SUP>-2</SUP>). Based on updated [O III] luminosities and intrinsic X-ray luminosities based on physical modeling of the hard X-ray spectra, we find that one galaxy was misclassified as type 2 (NGC 5005) and most of the remaining AGNs are obscured, including three confirmed as Compton thick (IC 3639, NGC 1386, and NGC 3982). One galaxy, NGC 3627, appears to have recently deactivated. Compared to the original sample that the nine AGNs were selected from, this is a rate of approximately 1%. We also find a new X-ray changing-look AGN in NGC 6890. | [
1447,
2035,
925,
2031
] | [
"seyfert galaxies",
"x-ray active galactic nuclei",
"liner galaxies",
"scaling relations"
] |
2021ApJ...914..141S | Culminating the Peak Cusp to Descry the Dark Side of Halos | The ConflUent System of Peak trajectories (CUSP) is a rigorous formalism in the framework of the peak theory that allows one to derive from first principles and no free parameters the typical halo properties from the statistics of peaks in the filtered Gaussian random field of density perturbations. The predicted halo mass function, spherically averaged density, velocity dispersion, velocity anisotropy, ellipticity, prolateness, and potential profiles, as well as the abundance and number density profiles of accreted and stripped subhalos and diffuse dark matter, accurately recover the results of cosmological N-body simulations. CUSP is thus a powerful tool for the calculation, in any desired hierarchical cosmology with Gaussian perturbations, of halo properties beyond the mass, redshift, and radial ranges covered by simulations. More importantly, CUSP unravels the origin of the characteristic features of those properties. In this paper, we culminate its construction. We show that all halo properties but those related to subhalo stripping are independent of the assembly history of those objects, and that the Gaussian is the only smoothing window able to find the finite collapsing patches while properly accounting for the entropy increase produced in major mergers. | [
1880,
730
] | [
"galaxy dark matter halos",
"hierarchical cosmology"
] |
2020ApJ...890....1N | Search for Eccentric Binary Neutron Star Mergers in the First and Second Observing Runs of Advanced LIGO | We present a search for gravitational waves from merging binary neutron stars (BNSs) which have non-negligible eccentricity as they enter the Laser Interferometer Gravitational Wave Observatory (LIGO) observing band. We use the public Advanced LIGO data which covers the period from 2015 through 2017 and contains ∼164 days of LIGO-Hanford and LIGO-Livingston coincident observing time. The search was conducted using matched-filtering using the PyCBC toolkit. We find no significant BNS candidates beyond GW170817, which has previously been reported by searches for binaries in circular orbits. We place a 90% upper limit of ∼1700 mergers Gpc<SUP>-3</SUP> yr<SUP>-1</SUP> for eccentricities ≲0.43 at a dominant-mode gravitational-wave frequency of 10 Hz. The absence of a detection with these data is consistent with theoretical predictions of eccentric BNS merger rates. Using our measured rate we estimate the sensitive volume of future gravitational-wave detectors and compare this to theoretical rate predictions. We find that, in the absence of a prior detection, the rate limits set by six months of Cosmic Explorer observations would constrain all current plausible models of eccentric BNS formation. | [
457,
678,
288,
1108
] | [
"elliptical orbits",
"gravitational waves",
"compact objects",
"neutron stars"
] |
2020ApJ...899L..14H | Axial Asymmetry Studies in Gaia Data Release 2 Yield the Pattern Speed of the Galactic Bar | Our recent studies of axial-symmetry breaking in the nearby (d < 3 kpc) star counts are sensitive to the distortions of stellar orbits perpendicular and parallel to the orientation of the bar just within and beyond the outer Lindblad resonance (OLR) radius. Using the location of the sign flip in the left-right asymmetry in stars counts about the anticenter line to determine the OLR radius R<SUB>OLR</SUB>, and treating the bar as if it were a weakly nonaxisymmetric effect, we use R<SUB>OLR</SUB> and recent measurements of the Galactic rotation curve and the Sun-Galactic-center distance R<SUB>0</SUB> to determine the pattern speed Ω<SUB>p</SUB> of the Galactic bar, as well as the Galactic corotation radius R<SUB>CR</SUB>. After removing the effect of the Large and Small Magellanic Clouds from our asymmetry measurement, we find that R<SUB>OLR</SUB> = (0.96 ± 0.03)R<SUB>0</SUB> = 7.85 ± 0.25 kpc, Ω<SUB>p</SUB> = 49.3 ± 2.2 km s<SUP>-1</SUP> kpc<SUP>-1</SUP>, R<SUB>CR</SUB> = (0.58 ± 0.04)R<SUB>0</SUB> = 4.76 ± 0.27 kpc, revealing, as we shall show, that the Milky Way's bar is likely both weak and fast, though we also note possible evidence for non-steady-state effects in the bar region. | [
2041,
565,
1051,
1059
] | [
"galactic bulge",
"galactic center",
"milky way dynamics",
"milky way rotation"
] |
2024ApJ...962..114B | Analysis of the 3.2–3.3 μm Interstellar Absorption Feature on Three Milky Way Sightlines | We report new analyses of spectra of the 3.2–3.3 μm absorption feature observed in the diffuse interstellar medium toward three Milky Way sources: 2MASS J17470898 ‑ 2829561 (2M1747) and the Quintuplet Cluster, both located in the Galactic center, and Cygnus OB2-12. The 3.2–3.3 μm interval coincides with the CH-stretching region for compact polycyclic aromatic hydrocarbons (PAHs). We focus on the 2M1747 spectrum. Its published optical depth spectrum contains residual telluric transmission features, which arise from the 0.06 difference in mean airmasses between the observations of the source and its telluric standard star. We corrected the published spectrum by adding the airmass residual optical depth spectrum. The corrected spectrum is well fit by a superposition of four Gaussians. The absorption spectra of the other two sources were also fit by four Gaussians, with similar central wavelengths, widths, and relative peak opacities. We associate the three longer wavelength Gaussians covering the 3.23–3.31 μm interval with compact PAHs in positive, neutral, and negative charge states. We identify the shortest-wavelength Gaussian, near 3.21 μm, with irregularly shaped PAHs. Constraints imposed by spectral smoothness on the corrected 2M1747 spectrum, augmented by a PAH cluster formation model for post-asymptotic giant branch stars, suggests that >99% of the PAHs in the diffuse interstellar medium reside in small clusters. This study supports the PAH hypothesis, and it suggests that a family of primarily compact PAHs with a C<SUB>66</SUB>H<SUB>20</SUB> (circumvalene) parent is consistent with the observed mid-infrared and ultraviolet interstellar absorption spectrum. | [
836,
837,
838,
201,
1280,
786,
2095,
75,
1736,
2121
] | [
"interstellar dust",
"interstellar dust extinction",
"interstellar dust processes",
"carbonaceous grains",
"polycyclic aromatic hydrocarbons",
"infrared astronomy",
"molecular spectroscopy",
"astrochemistry",
"ultraviolet astronomy",
"post-asymptotic giant branch stars"
] |
2024ApJS..271...29A | Image Synthesis for Solar Flare Prediction | Solar flare prediction is a topic of interest to many researchers owing to the potential of solar flares to affect various technological systems, both terrestrial and in orbit. In recent years, the forecasting task has become progressively more reliant on data-driven computations and machine-learning algorithms. Although these efforts have improved solar flare predictions, they still falter in doing so for large solar flares, in particular under operational conditions, since large-flare data are very scarce and labeled data are heavily imbalanced. In this work, we seek to address this fundamental issue and present a scheme for generating synthetic magnetograms to reduce the imbalance in the data. Our method consists of (1) synthetic oversampling of line-of-sight magnetograms using Gaussian mixture model representation, followed by (2) a global optimization technique to ensure consistency of both physical features and flare precursors, and (3) the mapping of the generated representations to realistic magnetogram images using deep generative models. We show that these synthetically generated data indeed improve the capacity of solar flare prediction models and that, when tested on such a state-of-the-art model, it significantly enhances its forecasting performance, achieving an F1-score as high as 0.43 ± 0.08 and a true skill statistic of 0.64 ± 0.10 for X-class flares in the 24 hr operational solar flare data split. | [
2037,
1974,
1933,
1937,
1496
] | [
"space weather",
"solar active regions",
"neural networks",
"gaussian mixture model",
"solar flares"
] |
2024AJ....168...66B | Discovery of the Remarkably Red L/T Transition Object VHS J183135.58-551355.9 | We present the discovery of VHS J183135.58‑551355.9 (hereafter VHS J1831‑5513), an L/T transition dwarf identified as a result of its unusually red near-infrared colors (J ‑ K <SUB>S</SUB> = 3.633 ± 0.277 mag; J ‑ W2 = 6.249 ± 0.245 mag) from the VISTA Hemisphere Survey and CatWISE2020 surveys. We obtain low-resolution near-infrared spectroscopy of VHS J1831‑5513 using the Magellan Folded port InfraRed Echellette spectrograph to confirm its extremely red nature and assess features sensitive to surface gravity (i.e., youth). Its near-infrared spectrum shows multiple CH<SUB>4</SUB> absorption features, indicating an exceptionally low effective temperature for its spectral type. Based on proper-motion measurements from CatWISE2020 and a photometric distance derived from its K <SUB> s </SUB>-band magnitude, we find that VHS J1831‑5513 is a likely (∼85% probability) kinematic member of the β Pictoris moving group. Future radial velocity and trigonometric parallax measurements will clarify such membership. Follow-up mid-infrared or higher-resolution near-infrared spectroscopy of this object will allow for further investigation as to the cause(s) of its redness, such as youth, clouds, and viewing geometry. | [
185,
894,
1679,
1582,
1076
] | [
"brown dwarfs",
"l dwarfs",
"t dwarfs",
"stellar associations",
"moving clusters"
] |
2024PASP..136d4501W | Assessing the Influence of Urban Lights on Night Sky Brightness with a Smartphone | The darkness of the sky is a critical parameter for assessing the suitability of an astronomical site. Among various sources of light pollution, urban lights pose the most significant threat to ground-based optical astronomical and planetary observations. Quantitatively assessing the impact of urban lights with varying scales and fluxes is indispensable for selecting an ideal optical observation site. In order to quantitatively assess the changes in Night Sky Brightness (NSB) relative to the distance from urban areas and to establish a foundation for safeguarding the light environment at the newly developed Lenghu astronomical site on the Tibetan Plateau, we employed both a Sky Quality Meter and a pre-calibrated smartphone. These instruments were used to measure the NSB in the vicinity of two cities, Da Qaidam and Delingha, which vary in size and radiant flux, on the Tibetan Plateau. The findings indicate that the NSB around both cities decreases significantly as the distance from the city center increases, although the rate of decrease varies between the two locations. This decline can be effectively modeled using an exponential decay function. Notably, the influence of city lights on NSB becomes negligible at distances exceeding 30 km from Da Qaidam, while for Delingha, this distance extends to 50 km due to its larger city size and higher total radiant flux. The methodologies and results presented in this paper offer valuable insights for the selection of astronomical observation sites and the development of light pollution management policies. | [
94,
113,
1689,
1112
] | [
"astronomical site protection",
"atmospheric effects",
"telescopes",
"night sky brightness"
] |
2024ApJ...967...81L | An Eccentric Planet Orbiting the Polar V808 Aurigae | We analyze 15 yr of eclipse timings of the polar V808 Aur. The rapid ingress/egress of the white dwarf and bright accretion region provide timings as precise as a few tenths of a second for rapid cadence photometric data. We find that between 2015 and 2018, the eclipse timings deviated from a linear ephemeris by more than 30 s. The rapid timing change is consistent with the periastron passage of a planet in an eccentric orbit about the polar. The best-fit orbital period is 11 ± 1 yr and we estimate a projected mass of $M\sin (i)=6.8\pm 0.7$ Jupiter masses. We also show that the eclipse timings are correlated with the brightness of the polar with a slope of 1.1 s mag<SUP>‑1</SUP>. This is likely due to the change in the geometry of the accretion curtains as a function of the mass transfer rate in the polar. While an eccentric planet offers an excellent explanation to the available eclipse data for V808 Aur, proposed planetary systems in other eclipsing polars have often struggled to accurately predict future eclipse timings. | [
203,
32,
489,
443,
1610
] | [
"cataclysmic variable stars",
"am herculis stars",
"exoplanet detection methods",
"eclipsing binary minima timing method",
"stellar magnetic fields"
] |
2022ApJ...933....4O | FAST Search for Circumstellar Atomic Hydrogen. I. The Young Planetary Nebula IC 4997 | Using the Five-hundred-meter Aperture Spherical radio Telescope in Guizhou, China, we detect the 21 cm neutral atomic hydrogen absorption in the young planetary nebula IC 4997. The absorption arises from a shell that is also associated with Na I D lines. The H I shell has a mass of 1.46 × 10<SUP>-2</SUP> M <SUB>⊙</SUB> and a dynamic age of 990 yr. The column density of H I is estimated to be 7.1 × 10<SUP>20</SUP> cm<SUP>-2</SUP>, which can be well explained in terms of a photodissociation region around the ionized nebula, limited by the self-shielding of H<SUB>2</SUB>. We find that the atomic-to-ionized hydrogen ratio is 0.6, suggesting that H I substantially contributes to the overall nebular mass. | [
1249,
1460,
237,
1613
] | [
"planetary nebulae",
"single-dish antennas",
"circumstellar envelopes",
"stellar mass loss"
] |
2022ApJ...932...68H | Radial Trapping of Thermal Rossby Waves within the Convection Zones of Low-mass Stars | We explore how thermal Rossby waves propagate within the gravitationally stratified atmosphere of a low-mass star with an outer convective envelope. Under the conditions of slow, rotationally constrained dynamics, we derive a local dispersion relation for atmospheric waves in a fully compressible stratified fluid. This dispersion relation describes the zonal and radial propagation of acoustic waves and gravito-inertial waves. Thermal Rossby waves are just one class of prograde-propagating gravito-inertial wave that manifests when the buoyancy frequency is small compared to the rotation rate of the star. From this dispersion relation, we identify the radii at which waves naturally reflect and demonstrate how thermal Rossby waves can be trapped radially in a waveguide that permits free propagation in the longitudinal direction. We explore this trapping further by presenting analytic solutions for thermal Rossby waves within an isentropically stratified atmosphere that models a zone of efficient convective heat transport. We find that, within such an atmosphere, waves of short zonal wavelength have a wave cavity that is radially thin and confined within the outer reaches of the convection zone near the star's equator. The same behavior is evinced by the thermal Rossby waves that appear at convective onset in numerical simulations of convection within rotating spheres. Finally, we suggest that stable thermal Rossby waves could exist in the lower portion of the Sun's convection zone, despite that region's unstable stratification. For long wavelengths, the Sun's rotation rate is sufficiently rapid to stabilize convective motions, and the resulting overstable convective modes are identical to thermal Rossby waves. | [
301,
1617,
1515,
1629,
1524,
819,
1963,
73,
709,
1998,
1281
] | [
"stellar convective zones",
"stellar oscillations",
"solar oscillations",
"stellar rotation",
"solar rotation",
"internal waves",
"hydrodynamics",
"asteroseismology",
"helioseismology",
"solar convective zone",
"polytropes"
] |
2023ApJ...942...69M | The Time-averaged Mass-loss Rates of Red Supergiants as Revealed by Their Luminosity Functions in M31 and M33 | Mass loss in red supergiants (RSGs) is generally recognized to be episodic, but mass-loss prescriptions fail to reflect this. Evolutionary models show that the total amount of mass lost in this phase determines if these stars evolve to warmer temperatures before undergoing core collapse. The current Geneva evolutionary models mimic episodic mass loss by enhancing the quiescent prescription rates whenever the star's outer layers exceed the Eddington luminosity by a large factor. This results in a 20 M <SUB>⊙</SUB> model undergoing 10× more mass loss than it would otherwise, but has little effect on models of lower mass. We can test the validity of this approach observationally by measuring the proportion of high-luminosity RSGs to that predicted by the models. To do this, we use our recent luminosity-limited census of RSGs in M31 and M33, making modest improvements to membership, and adopting extinctions based on the recent panchromatic M31 and M33 Hubble surveys. We then compare the proportions of the highest luminosity RSGs found to that predicted by published Geneva models, as well as to a special set of models computed without the enhanced rates. We find good agreement with the models which include the supra-Eddington enhanced mass loss. The models with lower mass-loss rates predict a larger fraction of high-luminosity RSGs than observed, and thus can be ruled out. We also use these improved data to confirm that the upper luminosity limit of RSGs is $\mathrm{log}L/{L}_{\odot }\sim 5.4$ , regardless of metallicity, using our improved data on M31 and M33 plus previous results on the Magellanic Clouds. | [
732,
1600,
1375,
1613
] | [
"massive stars",
"stellar evolutionary tracks",
"red supergiant stars",
"stellar mass loss"
] |
2021ApJ...914...54Y | Comparing the Inner and Outer Star-forming Complexes in the Nearby Spiral Galaxies NGC 628, NGC 5457, and NGC 6946 Using UVIT Observations | We present a far-UV (FUV) study of the star-forming complexes (SFCs) in three nearby galaxies using the Ultraviolet Imaging Telescope. The galaxies are close to face-on and show significant outer disk star formation. Two of them are isolated (NGC 628 and NGC 6946), and one is interacting with distant companions (NGC 5457). We compared the properties of the SFCs inside and outside the optical radius (R<SUB>25</SUB>). We estimated the sizes, star formation rates (SFRs), metallicities, and Toomre Q parameter of the SFCs. We find that the outer disk SFCs are at least 10 times smaller in area than those in the inner disk. The SFRs per unit area (Σ<SUB>SFR</SUB>) in both regions have similar mean values, but the outer SFCs have a much smaller range of Σ<SUB>SFR</SUB>. They are also metal-poor compared to the inner disk SFCs. The FUV emission is well correlated with the neutral hydrogen gas (H I) distribution and detected within and near several H I holes. Our estimation of the Q parameter in the outer disks of the two isolated galaxies suggests that their outer disks are stable (Q > 1). However, their FUV images indicate that there is ongoing star formation in these regions. This suggests that there may be some nonluminous mass or dark matter in their outer disks, which increases the disk surface density and supports the formation of local gravitational instabilities. In the interacting galaxy, NGC 5457, the baryonic surface density is sufficient (Q < 1) to trigger local disk instabilities in the outer disk. | [
1736,
1560,
600,
728
] | [
"ultraviolet astronomy",
"spiral galaxies",
"galaxy interactions",
"hi shells"
] |
2020ApJ...888...24B | On the Sensitivity of Heliosphere Models to the Uncertainty of the Low-energy Charge Exchange Cross-section | Models play an important role in our understanding of the global structure of the solar wind and its interaction with the interstellar medium. A critical ingredient in many types of models is the charge-exchange collisions between ions and neutrals. Some ambiguity exists in the charge-exchange cross-section for protons and hydrogen atoms, depending on which experimental data is used. The differences are greatest at low energies, and for the plasma-neutral interaction in the outer heliosheath may exceed 50%. In this paper we assess a number of existing data sets and formulae for proton-hydrogen charge exchange. We use a global simulation of the heliosphere to quantify the differences between the currently favored cross-section, and we suggest a formulation that more closely matches the majority of available data. We find that in order to make the resulting two heliospheres the same size, the interstellar proton and hydrogen densities need to be adjusted by 10%-15%, which provides a way to link the uncertainty in the cross-section to the uncertainty in the parameters of the pristine interstellar plasma. | [
711,
710,
106,
2056
] | [
"heliosphere",
"heliosheath",
"astrosphere interstellar medium interactions",
"charge exchange ionization"
] |
2023ApJ...943...31M | The High-resolution Soft X-Ray Spectrum of Nova Delphini 2013 | We present the high-resolution soft X-ray spectrum of Nova Delphini 2013. Two spectra were taken with the Low Energy Transmission Grating Spectrometer on the Chandra X-ray Observatory, on 2013 November 9 and 2013 December 6, 87 and 114 days after the nova eruption, respectively. The spectra are of very high statistical quality, and reveal clear spectral evolution between the two observations. The source is bright enough on the two occasions that the third spectral order, with resolving power up to ~3000, can easily be seen. We observe the photospheric emission spectrum of the hot white dwarf, which exhibits a rich absorption line spectrum from an atmosphere of effective temperature likely near T <SUB>eff</SUB> ~ 640,000 K, and complex chemical abundances. Superimposed on this photospheric spectrum, we detect the absorption spectrum of a shell of highly ionized gas, comprising absorption by the K-shell ions of C and N, blueshifted (outflowing) by ~1400 km s<SUP>-1</SUP>, and with a velocity width of ~1000 km s<SUP>-1</SUP>. The abundance ratio C/N is clearly very nonsolar, and indicative of thermonuclear fusion by the CNO cycle. We discuss the physical properties (kinematics, ionization balance, radiative transfer, mechanical energy balance, chemical abundances) of this hot shell, in the context of the physics of nova eruptions. | [
1127,
2096,
242
] | [
"novae",
"high resolution spectroscopy",
"circumstellar shells"
] |
2022ApJ...928...20B | New Variable Hot Subdwarf Stars Identified from Anomalous Gaia Flux Errors, Observed by TESS, and Classified via Fourier Diagnostics | Hot subdwarf stars are mostly stripped red giants that can exhibit photometric variations due to stellar pulsations, eclipses, the reflection effect, ellipsoidal modulation, and Doppler beaming. Detailed studies of their light curves help constrain stellar parameters through asteroseismological analyses or binary light-curve modeling and generally improve our capacity to draw a statistically meaningful picture of this enigmatic stage of stellar evolution. From an analysis of Gaia DR2 flux errors, we have identified around 1200 candidate hot subdwarfs with inflated flux errors for their magnitudes-a strong indicator of photometric variability. As a pilot study, we obtained 2 minute cadence TESS Cycle 2 observations of 187 candidate hot subdwarfs with anomalous Gaia flux errors. More than 90% of our targets show significant photometric variations in their TESS light curves. Many of the new systems found are cataclysmic variables, but we report the discovery of several new variable hot subdwarfs, including HW Vir binaries, reflection-effect systems, pulsating sdBV<SUB> s </SUB> stars, and ellipsoidally modulated systems. We determine atmospheric parameters for select systems using follow-up spectroscopy from the 3 m Shane telescope. Finally, we present a Fourier diagnostic plot for classifying binary light curves using the relative amplitudes and phases of their fundamental and harmonic signals in their periodograms. This plot makes it possible to identify certain types of variables efficiently, without directly investigating their light curves, and may assist in the rapid classification of systems observed in large photometric surveys. | [
129,
1671,
154,
444,
254,
1453
] | [
"b subdwarf stars",
"surveys",
"binary stars",
"eclipsing binary stars",
"close binary stars",
"short period variable stars"
] |
2023ApJ...951....6A | Pixelated Reconstruction of Foreground Density and Background Surface Brightness in Gravitational Lensing Systems Using Recurrent Inference Machines | Modeling strong gravitational lenses in order to quantify distortions in the images of background sources and to reconstruct the mass density in foreground lenses has been a difficult computational challenge. As the quality of gravitational lens images increases, the task of fully exploiting the information they contain becomes computationally and algorithmically more difficult. In this work, we use a neural network based on the recurrent inference machine to reconstruct simultaneously an undistorted image of the background source and the lens mass density distribution as pixelated maps. The method iteratively reconstructs the model parameters (the image of the source and a pixelated density map) by learning the process of optimizing the likelihood given the data using the physical model (a ray-tracing simulation), regularized by a prior implicitly learned by the neural network through its training data. When compared to more traditional parametric models, the proposed method is significantly more expressive and can reconstruct complex mass distributions, which we demonstrate by using realistic lensing galaxies taken from the IllustrisTNG cosmological hydrodynamic simulation. | [
1938,
1857,
1903
] | [
"convolutional neural networks",
"astronomical simulations",
"nonparametric inference"
] |
2022ApJ...937...72N | Survival of Terrestrial N<SUB>2</SUB>-O<SUB>2</SUB> Atmospheres in Violent XUV Environments through Efficient Atomic Line Radiative Cooling | Atmospheres play a crucial role in planetary habitability. Around M dwarfs and young Sun-like stars, planets receiving the same insolation as the present-day Earth are exposed to intense stellar X-rays and extreme-ultraviolet (XUV) radiation. This study explores the fundamental question of whether the atmosphere of present-day Earth could survive in such harsh XUV environments. Previous theoretical studies suggest that stellar XUV irradiation is sufficiently intense to remove such atmospheres completely on short timescales. In this study, we develop a new upper-atmospheric model and re-examine the thermal and hydrodynamic responses of the thermospheric structure of an Earth-like N<SUB>2</SUB>-O<SUB>2</SUB> atmosphere, on an Earth-mass planet, to an increase in the XUV irradiation. Our model includes the effects of radiative cooling via electronic transitions of atoms and ions, known as atomic line cooling, in addition to the processes accounted for by previous models. We demonstrate that atomic line cooling dominates over the hydrodynamic effect at XUV irradiation levels greater than several times the present level of the Earth. Consequentially, the atmosphere's structure is kept almost hydrostatic, and its escape remains sluggish even at XUV irradiation levels up to a thousand times that of the Earth at present. Our estimates for the Jeans escape rates of N<SUB>2</SUB>-O<SUB>2</SUB> atmospheres suggest that these 1 bar atmospheres survive in early active phases of Sun-like stars. Even around active late M dwarfs, N<SUB>2</SUB>-O<SUB>2</SUB> atmospheres could escape significant thermal loss on timescales of gigayears. These results give new insights into the habitability of terrestrial exoplanets and the Earth's climate history. | [
498,
487,
437,
695,
1748
] | [
"exoplanets",
"exoplanet atmospheres",
"earth atmosphere",
"habitable planets",
"upper atmosphere"
] |
2021ApJ...911L..13L | Tiny-scale Structure Discovered toward PSR B1557-50 | Optical depth variations in the Galactic neutral interstellar medium (ISM) with spatial scales from hundreds to thousands of astronomical units have been observed through H I absorption against pulsars and continuum sources, while extremely small structures with spatial scales of tens of astronomical units remain largely unexplored. The nature and formation of such tiny-scale atomic structures (TSAS) need to be better understood. We report a tentative detection of TSAS with a signal-to-noise ratio of 3.2 toward PSR B1557-50 in the second epoch of two Parkes sessions just 0.36 yr apart, which are the closest-spaced spectral observations toward this pulsar. One absorption component showing marginal variations has been identified. Based on the pulsar's proper motion of 14 mas yr<SUP>-1</SUP> and the component's kinematic distance of 3.3 kpc, the corresponding characteristic spatial scale is 17 au, which is among the smallest sizes of known TSAS. Assuming a similar line-of-sight (LOS) depth, the tentative TSAS cloud detected here is overdense and overpressured relative to the cold neutral medium (CNM), and can radiatively cool fast enough to be in thermal equilibrium with the ambient environment. We find that turbulence is not sufficient to confine the overpressured TSAS. We explore the LOS elongation that would be required for the tentative TSAS to be at the canonical CNM pressure, and find that it is ∼5000—much larger than filaments observed in the ISM. We see some evidence of line width and temperature variations in the CNM components observed at the two epochs, as predicted by models of TSAS-like cloud formation colliding warm neutral medium flows. | [
847,
831,
834,
1353,
1306,
690,
395,
266,
1789
] | [
"interstellar medium",
"interstellar absorption",
"interstellar clouds",
"radio pulsars",
"pulsars",
"h i line emission",
"distance measure",
"cold neutral medium",
"warm neutral medium"
] |
2020ApJ...893...52H | A Deep Exposure in High Resolution X-Rays Reveals the Hottest Plasma in the ζ Puppis Wind | We have obtained a very deep exposure (813 ks) of ζ Puppis (O4 supergiant) with the Chandra HETG Spectrometer. Here we report on analysis of the 1-9 Å region, especially well suited for Chandra, which has a significant contribution from continuum emission between well separated emission lines from high-ionization species. These data allow us to study the hottest plasma present through the continuum shape and emission line strengths. Assuming a power-law emission measure distribution that has a high-temperature cutoff, we find that the emission is consistent with a thermal spectrum having a maximum temperature of 12 MK as determined from the corresponding spectral cutoff. This implies an effective wind shock velocity of 900 km s<SUP>-1</SUP>, well below the wind terminal speed of 2250 km s<SUP>-1</SUP>. For X-ray emission that forms close to the star, the speed and X-ray flux are larger than can be easily reconciled with strictly self-excited line-deshadowing-instability models, suggesting a need for a fraction of the wind to be accelerated extremely rapidly right from the base. This is not so much a dynamical instability as a nonlinear response to changing boundary conditions. | [
1137,
1823,
1636
] | [
"o stars",
"x-ray stars",
"stellar winds"
] |
2020ApJ...902..118S | A Survey of 3-5.4 μm Emission from Planetary Nebulae Using SOFIA/FLITECAM | Here we present the results of an airborne 3-5.4 μm spectroscopic study of three young, carbon-rich planetary nebulae (PNs) IC 5117, PNG 093.9-00.1, and BD +30 3639. These observations were made using the grism spectroscopy mode of the First Light Infrared TEst CAMera (FLITECAM) instrument during airborne science operations on board NASA's Stratospheric Observatory for Infrared Astronomy (SOFIA). The goal of this study is to characterize the 3.3 and 5.25 μm polycyclic aromatic hydrocarbon (PAH) dust emission in PNs and study the evolution of PAH features within evolved stars before their incorporation into new stellar systems in star-forming regions. Targets were selected from Infrared Astronomical Satellite, Kuiper Airborne Observatory and Infrared Space Observatory source lists, and were previously observed with FLITECAM on the 3 m Shane telescope at Lick Observatory to allow direct comparison between the ground and airborne observations. We measure PAH emission equivalent width and central wavelength, classify the shape of the PAH emission, and determine the PAH/aliphatic ratio for each target. The 3.3 μm PAH emission feature is observed in all three objects. PNG 093.9-00.1 exhibits NGC 7027-like aliphatic emission in the 3.4-3.6 μm region while IC 5117 and BD +30 3639 exhibit less aliphatic structure. All three PNs additionally exhibit PAH emission at 5.25 μm. | [
786,
1249,
1280,
2121,
1558,
791
] | [
"infrared astronomy",
"planetary nebulae",
"polycyclic aromatic hydrocarbons",
"post-asymptotic giant branch stars",
"spectroscopy",
"infrared observatories"
] |
2023ApJ...958...97X | Predicting the Radiation Field of Molecular Clouds Using Denoising Diffusion Probabilistic Models | Accurately quantifying the impact of radiation feedback in star formation is challenging. To address this complex problem, we employ deep-learning techniques known as denoising diffusion probabilistic models (DDPMs) to predict the interstellar radiation field (ISRF) strength based on three-band dust emission at 4.5, 24, and 250 μm. We adopt magnetohydrodynamic simulations from the STARFORGE project that model star formation and giant molecular cloud (GMC) evolution. We generate synthetic dust emission maps matching observed spectral energy distributions in the Monoceros R2 (MonR2) GMC. We train DDPMs to estimate the ISRF using synthetic three-band dust emission. The dispersion between the predictions and true values is within a factor of 0.1 for the test set. We extended our assessment of the diffusion model to include new simulations with varying physical parameters. While there is a consistent offset observed in these out-of-distribution simulations, the model effectively constrains the relative intensity to within a factor of 2. Meanwhile, our analysis reveals a weak correlation between the ISRF solely derived from dust temperature and the actual ISRF. We apply our trained model to predict the ISRF in MonR2, revealing a correspondence between intense ISRF, bright sources, and high dust emission, confirming the model's ability to capture ISRF variations. Our model robustly predicts radiation feedback distribution, even in complex, poorly constrained ISRF environments like those influenced by nearby star clusters. However, precise ISRF predictions require an accurate training data set mirroring the target molecular cloud's unique physical conditions. | [
847,
836,
852,
1882,
1886,
1072,
1964,
1834
] | [
"interstellar medium",
"interstellar dust",
"interstellar radiation field",
"astrostatistics",
"astrostatistics techniques",
"molecular clouds",
"magnetohydrodynamics",
"young stellar objects"
] |
2023RNAAS...7...92J | The Recent Mass Loss History of the Hypergiant RW Cep | In light of recent variability seen in RW Cep, we present an analysis of the spectral energy distribution of the star and unpublished, high spatial resolution mid-Infrared imaging. We derive a current mass-loss rate of ~7 × 10<SUP>-6</SUP> M <SUB>⊙</SUB> yr<SUP>-1</SUP> for the star and clear evidence of a higher mass-loss rate phase ending no more than ~100 yr ago. | [
774
] | [
"hypergiant stars"
] |
2020ApJ...900...24W | Thermal and Orbital Evolution of Low-mass Exoplanets | The thermal, orbital, and rotational dynamics of tidally loaded exoplanets are interconnected by intricate feedback. The rheological structure of the planet determines its susceptibility to tidal deformation and, as a consequence, participates in shaping its orbit. The orbital parameters and the spin state, conversely, control the rate of tidal dissipation and may lead to substantial changes in the interior. We investigate the coupled thermal-orbital evolution of differentiated rocky exoplanets governed by the Andrade viscoelastic rheology. The coupled evolution is treated by a semianalytical model, 1D parameterized heat transfer, and self-consistently calculated tidal dissipation. First, we conduct several parametric studies, exploring the effect of the rheological properties, the planet size, and the orbital eccentricity on tidal locking and dissipation. These tests show that the role of tidal locking into high spin-orbit resonances is most prominent on low eccentric orbits, where it results in substantially higher tidal heating than synchronous rotation. Second, we calculate the long-term evolution of three currently known low-mass exoplanets with nonzero orbital eccentricity and absent or yet-unknown eccentricity forcing (namely GJ 625 b, GJ 411 b, and Proxima Centauri b). The tidal model incorporates the formation of a stable magma ocean and a consistently evolving spin rate. We find that the thermal state is strongly affected by the evolution of eccentricity and spin state and proceeds as a sequence of thermal equilibria. Final despinning into synchronous rotation slows down the orbital evolution and helps to maintain long-term stable orbital eccentricity. | [
497,
490,
498,
511,
1699,
1178,
1698
] | [
"exoplanet tides",
"exoplanet dynamics",
"exoplanets",
"extrasolar rocky planets",
"tidal interaction",
"orbital evolution",
"tidal friction"
] |
2023ApJ...956L...6L | Outlier Detection in the DESI Bright Galaxy Survey | We present an unsupervised search for outliers in the Bright Galaxy Survey (BGS) data set from the DESI Early Data Release. This analysis utilizes an autoencoder to compress galaxy spectra into a compact, redshift-invariant latent space, and a normalizing flow to identify low-probability objects. The most prominent outliers show distinctive spectral features, such as irregular or double-peaked emission lines or originate from galaxy mergers, blended sources, and rare quasar types, including one previously unknown broad absorption line system. A significant portion of the BGS outliers are stars spectroscopically misclassified as galaxies. By building our own star model trained on spectra from the DESI Milky Way Survey, we have determined that the misclassification likely stems from the principle component analysis of stars in the DESI pipeline. To aid follow-up studies, we make the full probability catalog of all BGS objects and our pretrained models publicly available. | [
2171,
1934
] | [
"galaxy spectroscopy",
"outlier detection"
] |
2024ApJ...965..104F | Latent Stochastic Differential Equations for Modeling Quasar Variability and Inferring Black Hole Properties | Quasars are bright and unobscured active galactic nuclei (AGN) thought to be powered by the accretion of matter around supermassive black holes at the centers of galaxies. The temporal variability of a quasar's brightness contains valuable information about its physical properties. The UV/optical variability is thought to be a stochastic process, often represented as a damped random walk described by a stochastic differential equation (SDE). Upcoming wide-field telescopes such as the Rubin Observatory Legacy Survey of Space and Time (LSST) are expected to observe tens of millions of AGN in multiple filters over a ten year period, so there is a need for efficient and automated modeling techniques that can handle the large volume of data. Latent SDEs are machine learning models well suited for modeling quasar variability, as they can explicitly capture the underlying stochastic dynamics. In this work, we adapt latent SDEs to jointly reconstruct multivariate quasar light curves and infer their physical properties such as the black hole mass, inclination angle, and temperature slope. Our model is trained on realistic simulations of LSST ten year quasar light curves, and we demonstrate its ability to reconstruct quasar light curves even in the presence of long seasonal gaps and irregular sampling across different bands, outperforming a multioutput Gaussian process regression baseline. Our method has the potential to provide a deeper understanding of the physical properties of quasars and is applicable to a wide range of other multivariate time series with missing data and irregular sampling. | [
1319,
16,
1933,
1916,
1953
] | [
"quasars",
"active galactic nuclei",
"neural networks",
"time series analysis",
"irregular cadence"
] |
2023ApJ...950L..19F | Astrometric Accelerations as Dynamical Beacons: A Giant Planet Imaged inside the Debris Disk of the Young Star AF Lep | We present the direct-imaging discovery of a giant planet orbiting the young star AF Lep, a 1.2 M <SUB>⊙</SUB> member of the 24 ± 3 Myr β Pic moving group. AF Lep was observed as part of our ongoing high-contrast imaging program targeting stars with astrometric accelerations between Hipparcos and Gaia that indicate the presence of substellar companions. Keck/NIRC2 observations in $L^{\prime} $ with the vector vortex coronagraph reveal a point source, AF Lep b, at ≈340 mas, which exhibits orbital motion at the 6σ level over the course of 13 months. A joint orbit fit yields precise constraints on the planet's dynamical mass of ${3.2}_{-0.6}^{+0.7}$ M <SUB>Jup</SUB>, semimajor axis of ${8.4}_{-1.3}^{+1.1}$ au, and eccentricity of ${0.24}_{-0.15}^{+0.27}$ . AF Lep hosts a debris disk located at ~50 au, but it is unlikely to be sculpted by AF Lep b, implying there may be additional planets in the system at wider separations. The stellar inclination (i <SUB>*</SUB> = ${54}_{-9}^{{+11}^\circ} $ ) and orbital inclination (i <SUB> o </SUB> = ${50}_{-12}^{{+9}^\circ} $ ) are in good agreement, which is consistent with the system having spin-orbit alignment. AF Lep b is the lowest-mass imaged planet with a dynamical mass measurement and highlights the promise of using astrometric accelerations as a tool to find and characterize long-period planets. | [
509,
2130,
387,
1175,
363
] | [
"extrasolar gaseous giant planets",
"astrometric exoplanet detection",
"direct imaging",
"orbit determination",
"debris disks"
] |
2023ApJ...945L..31R | Unified Picture of the Local Interstellar Magnetic Field from Voyager and IBEX | Prior to the Voyagers' heliopause crossings, models and the community expected the magnetic field to show major rotations across the boundary. Surprisingly, the field showed no significant change in direction from the heliospheric Parker Spiral at either Voyager location. Meanwhile, a major result from the IBEX mission is the derived magnitude and direction of the interstellar field far from the Sun (~1000 au) beyond the influence of the heliosphere. Using a self-consistent model fit to IBEX ribbon data, Zirnstein et al. reported that this "pristine" local interstellar magnetic field has a magnitude of 0.293 nT and direction of 227° in ecliptic longitude and 34.°6 in ecliptic latitude. These values differ by 27% (51%) and 44° (12°) from what Voyager 1 (2) currently observes (as of ~2022.75). While differences are to be expected as the field undrapes away from the heliosphere, the global structure of the draping across hundreds of astronimcal units has not been reconciled. This leads to several questions: How are these distinct sets of observations reconcilable? What is the interstellar magnetic field's large-scale structure? How far out would a future mission need to go to sample the unperturbed field? Here, we show that if realistic errors are included for the difficult-to-calibrate radial field component, the measured transverse field is consistent with that predicted by IBEX, allowing us to answer these questions through a unified picture of the behavior of the local interstellar magnetic field from its draping around the heliopause to its unfolding into the pristine interstellar medium. | [
824,
711,
707,
710,
851,
1261,
1544,
847,
106
] | [
"interplanetary magnetic fields",
"heliosphere",
"heliopause",
"heliosheath",
"interstellar plasma",
"plasma astrophysics",
"space plasmas",
"interstellar medium",
"astrosphere interstellar medium interactions"
] |
2020RNAAS...4...12P | A Catalog of Galactic Multiple Systems with a Red Supergiant and a B Star | Binary systems composed of a red supergiant and a B star are useful probes of stellar evolution. We have searched the literature to create a catalog of 108 Galactic systems of such type, which is presented here. | [
154,
205,
430,
909,
910,
1375,
128
] | [
"binary stars",
"catalogs",
"early-type stars",
"late-type stars",
"late-type supergiant stars",
"red supergiant stars",
"b stars"
] |
2023PSJ.....4..165J | Radar Observations of the Arid Meteor Shower Outburst from Comet 15P/Finlay | We report on observations of the anticipated, first time occurrence, Arid meteor shower produced by comet 15P/Finlay. This comet, which has not been noteworthy for over a century, produced two major outbursts of activity during perihelion passage between 2014 December and 2015 January. Various authors predicted that Earth would cross the resulting ejecta on 2021 October 6-7 UT with a radiant in the constellation Ara, optimally placed to be observed from the Southern Hemisphere. We observed two outbursts using the Southern Argentina Agile Meteor Radar-Orbital System: one on 2021 September 29 and a second more dominant peak on 2021 October 7, centered around α = 260.°34, δ = -57.°63 and α = 255.°01, δ = -48.°47, respectively. The 6.5 mag limit flux and zenithal hourly rates were 0.073 meteors km<SUP>-2</SUP> hr<SUP>-1</SUP> and 491 hr<SUP>-1</SUP>, respectively. The time of occurrence of the two detected peaks are in good agreement with predictions of this shower reported by several authors, confirming the validity of the models used for the predictions. | [
1034,
1041,
2287
] | [
"meteor showers",
"meteors",
"radar observations"
] |
2023ApJ...943...34S | Tracking the Rapid Opening and Closing of Polar Coronal Holes through IBEX ENA Observations | Fast solar wind (SW) flows outward from polar coronal holes (PCHs). The latitudinal extent of the fast SW varies during different phases of the solar cycle. The fast SW in the inner heliosheath produces a flatter proton spectrum than the slow SW that can be observed through energetic neutral atoms (ENAs) by the Interstellar Boundary Explorer (IBEX). In this study, we investigate the evolution of PCHs as reflected in the high-time resolution ENA flux measurements from IBEX-Hi, where the PCHs are identified by ENA spectral indices <1.8. The ENA spectral index over the poles shows a periodic evolution over the solar cycle 24. The surface area with flatter ENA spectra (<1.8) around the ecliptic south pole increases slightly from 2009-2011 and then decreased gradually from 2012-2014. The PCH completely disappears in 2016 and then starts to appear again starting in 2017, gradually growing until 2019. This evolution shows a clear correlation with the change in the PCH area observed at the Sun once the delay in the ENA observation time is included. In addition, the higher-cadence ENA data at the highest latitudes show a rapid evolution of the ENA spectrum near the south pole in 2014 and 2017. The rapid evolution in 2014 is related to a rapid closing of PCHs in 2012 and that in 2017 is related to a rapid opening of PCHs in late 2014. These results also agree qualitatively with the evolution of the ENA spectral index from simulations using a simple time-dependent heliospheric flow model. | [
1534,
1484,
1239,
711,
710,
2056,
1690,
1553
] | [
"solar wind",
"solar coronal holes",
"pickup ions",
"heliosphere",
"heliosheath",
"charge exchange ionization",
"termination shock",
"spectral index"
] |
2024AJ....167...30H | Variability in Protoplanetary Nebulae. X. Multiyear Periods as an Indicator of Potential Binaries | New observations are presented of four evolved objects that display long, multiyear variations in their light curves. These are interpreted as good evidence of their binary nature, with the modulation caused by the barycenter motion of the evolved star resulting in a periodic obscuration by a circumbinary disk. Although protoplanetary nebulae (PPNe) commonly possess bipolar nebulae, which are thought to be shaped by a binary companion, there are very few PPNe in which a binary companion has been found. Three of the objects in this study appear to be PPNe, IRAS 07253-2001, 08005-2356, and 17542-0603, with long periods of 5.2, 6.9, and 8.2 yr, respectively. The binary nature of IRAS 08005-2356 has recently been confirmed by a radial velocity study. Two samples, one of PPNe and the other of post-AGB star candidates, are investigated for further evidence on how common is a long-period light-curve variation. Both samples suggest such light-curve variations are not common. The fourth object, IRAS 20056+1834 (QY Sge), is an obscured RV Tau variable of the RVb subclass, with a long period of 3.9 yr and pulsation periods of 102.9 and 51.5 days. The period of this object is seen to vary by 2%. Evidence is presented for a recent mass ejection in IRAS 17542-0603. | [
2121,
481,
154,
935,
1418,
1301
] | [
"post-asymptotic giant branch stars",
"evolved stars",
"binary stars",
"long period variable stars",
"rv tauri variable stars",
"protoplanetary nebulae"
] |
2020ApJ...893L..26I | A Binary Comb Model for Periodic Fast Radio Bursts | We show that the periodic FRB 180916.J0158+65 can be interpreted by invoking an interacting neutron star binary system with an orbital period of ∼16 days. The FRBs are produced by a highly magnetized pulsar, whose magnetic field is "combed" by the strong wind from a companion star, either a massive star or a millisecond pulsar. The FRB pulsar wind retains a clear funnel in the companion's wind that is otherwise opaque to induced Compton or Raman scatterings for repeating FRB emission. The 4 day active window corresponds to the time when the funnel points toward Earth. The interaction also perturbs the magnetosphere of the FRB pulsar and may trigger emission of FRBs. We derive the physical constraints on the comb and the FRB pulsar from the observations and estimate the event rate of FRBs. In this scenario, a lower limit on the period of observable FRBs is predicted. We speculate that both the intrinsic factors (strong magnetic field and young age) and the extrinsic factor (interaction) may be needed to generate FRBs in neutron star binary systems. | [
2008,
153,
1108,
992,
1119,
1391,
994,
1212
] | [
"radio transient sources",
"binary pulsars",
"neutron stars",
"magnetars",
"non-thermal radiation sources",
"relativistic mechanics",
"magnetic fields",
"periodic orbit"
] |
2021ApJ...923..231S | VLA and NOEMA Views of Bok Globule CB 17: The Starless Nature of a Proposed First Hydrostatic Core Candidate | We use 3 mm continuum NOrthern Extended Millimeter Array and NH<SUB>3</SUB> Very Large Array observations toward the First Hydrostatic Core (FHSC) candidate CB 17 MMS in order to reveal the dust structure and gas properties to 600–1100 au scales and to constrain its evolutionary stage. We do not detect any compact source at the previously identified 1.3 mm point source, despite expecting a minimum signal-to-noise ratio of 9. The gas traced by NH<SUB>3</SUB> exhibits subsonic motions, with an average temperature of 10.4 K. A fit of the radial column density profile derived from the ammonia emission finds a flat inner region of radius ∼1800 au and a central density of ∼6 × 10<SUP>5</SUP> cm<SUP>‑3</SUP>. Virial and density structure analysis reveals the core is marginally bound (α <SUB>vir</SUB> = 0.73). The region is entirely consistent with that of a young starless core, hence ruling out CB 17 MMS as an FHSC candidate. Additionally, the core exhibits a velocity gradient aligned with the major axis, showing an arc-like structure in the position–velocity diagram and an off-center region with high velocity dispersion, caused by two distinct velocity peaks. These features could be due to interactions with the nearby outflow, which appears to deflect due to the dense gas near the NH<SUB>3</SUB> column density peak. We investigate the specific angular momentum profile of the starless core, finding that it aligns closely with previous studies of similar radial profiles in Class 0 sources. This similarity to more evolved objects suggests that motions at 1000 au scales are determined by large-scale dense cloud motions, and may be preserved throughout the early stages of star formation. | [
1569,
1302,
171,
808,
847
] | [
"star formation",
"protostars",
"bok globules",
"interferometry",
"interstellar medium"
] |
2021AJ....161..174M | Phase-curve Pollution of Exoplanet Transmission Spectra | The occurrence of a planet transiting in front of its host star offers the opportunity to observe the planet's atmosphere filtering starlight. The fraction of occulted stellar flux is roughly proportional to the optically thick area of the planet, the extent of which depends on the opacity of the planet's gaseous envelope at the observed wavelengths. Chemical species, haze, and clouds are now routinely detected in exoplanet atmospheres through rather small features in transmission spectra, i.e., collections of planet-to-star area ratios across multiple spectral bins and/or photometric bands. Technological advances have led to a shrinking of the error bars down to a few tens of parts per million (ppm) per spectral point for the brightest targets. The upcoming James Webb Space Telescope (JWST) is anticipated to deliver transmission spectra with precision down to 10 ppm. The increasing precision of measurements requires a reassessment of the approximations hitherto adopted in astrophysical models, including transit light-curve models. Recently, it has been shown that neglecting the planet's thermal emission can introduce significant biases in the transit depth measured with the JWST/Mid-InfraRed Instrument, integrated between 5 and 12 μm. In this paper, we take a step forward by analyzing the effects of the approximation on transmission spectra over the 0.6-12 μm wavelength range covered by various JWST instruments. We present open-source software to predict the spectral bias, showing that, if not corrected, it may affect the inferred molecular abundances and thermal structure of some exoplanet atmospheres. | [
487,
2133,
484,
498,
791
] | [
"exoplanet atmospheres",
"transmission spectroscopy",
"exoplanet systems",
"exoplanets",
"infrared observatories"
] |
2022ApJ...932...91M | Where to Find Overmassive Brown Dwarfs: New Benchmark Systems for Binary Evolution | Under the right conditions, brown dwarfs that gain enough mass late in their lives to cross the hydrogen-burning limit will not turn into low-mass stars, but rather remain essentially brown dwarf-like. While these objects, called either beige dwarfs or overmassive brown dwarfs, may exist in principle, it remains unclear exactly how they would form astrophysically. We show that accretion from AGB winds, aided by the wind Roche lobe overflow mechanism, is likely to produce a substantial population of observable overmassive brown dwarfs, though other mechanisms are still plausible. Specifically, we predict that Sun-like stars born with a massive brown dwarf companion on an orbit with a semimajor axis of order 10 au will likely produce overmassive brown dwarfs, which may be found today as companions to the donor star's remnant white dwarf. The identification and characterization of such an object would produce unique constraints on binary evolution, because there is a solid upper limit on the brown dwarf's initial mass. | [
185,
2052,
1599,
154,
2100,
1799,
2050
] | [
"brown dwarfs",
"stellar evolutionary types",
"stellar evolution",
"binary stars",
"asymptotic giant branch stars",
"white dwarf stars",
"low mass stars"
] |
2022ApJ...930..121W | Spectral Line Depth Variability in Radial Velocity Spectra | Stellar active regions, including spots and faculae, can create radial velocity (RV) signals that interfere with the detection and mass measurements of low-mass exoplanets. In doing so, these active regions affect each spectral line differently, but the origin of these differences is not fully understood. Here we explore how spectral line variability correlated with S-index (Ca H and K emission) is related to the atomic properties of each spectral line. Next, we develop a simple analytic stellar atmosphere model that can account for the largest sources of line variability with S-index. Then, we apply this model to HARPS spectra of α Cen B to explain Fe I line depth changes in terms of a disk-averaged temperature difference between active and quiet regions on the visible hemisphere of the star. This work helps establish a physical basis for understanding how stellar activity manifests differently in each spectral line and may help future work mitigating the impact of stellar activity on exoplanet RV surveys. | [
1332,
1601,
489,
1580
] | [
"radial velocity",
"stellar faculae",
"exoplanet detection methods",
"stellar activity"
] |
2023PASP..135f4503Z | Regularized Maximum Likelihood Image Synthesis and Validation for ALMA Continuum Observations of Protoplanetary Disks | Regularized Maximum Likelihood (RML) techniques are a class of image synthesis methods that achieve better angular resolution and image fidelity than traditional methods like CLEAN for sub-mm interferometric observations. To identify best practices for RML imaging, we used the GPU-accelerated open source Python package MPoL, a machine learning-based RML approach, to explore the influence of common RML regularizers (maximum entropy, sparsity, total variation, and total squared variation) on images reconstructed from real and synthetic Atacama Large millimeter/submillimeter Array (ALMA) continuum observations of protoplanetary disks. We tested two different cross-validation (CV) procedures to characterize their performance and determine optimal prior strengths, and found that CV over a coarse grid of regularization strengths easily identifies a range of models with comparably strong predictive power. To evaluate the performance of RML techniques against a ground truth image, we used MPoL on a synthetic protoplanetary disk data set and found that RML methods successfully resolve structures at fine spatial scales present in the original simulation. We used ALMA DSHARP observations of the protoplanetary disk around HD 143006 to compare the performance of MPoL and CLEAN, finding that RML imaging improved the spatial resolution of the image by up to a factor of 3 without sacrificing sensitivity. We provide general recommendations for building an RML workflow for image synthesis of ALMA protoplanetary disk observations, including effective use of CV. Using these techniques to improve the imaging resolution of protoplanetary disk observations will enable new science, including the detection of protoplanets embedded in disks. | [
1300,
1647,
1346,
1910,
1866
] | [
"protoplanetary disks",
"submillimeter astronomy",
"radio interferometry",
"deconvolution",
"open source software"
] |
2021ApJ...908..173G | White Dwarf Photospheric Abundances in Cataclysmic Variables. I. SS Aurigae and TU Mensae | Chemical abundance studies of cataclysmic variables have revealed high nitrogen to carbon ratios in a number of cataclysmic variable white dwarfs (based on ultraviolet emission and absorption lines), as well as possible carbon deficiency in many secondaries (based on the absence of infrared CO absorption lines). These indicate that the accreted material on the white dwarf surface and the donor itself might be contaminated with CNO processed material. To further understand the origin of this abundance anomaly, there is a need for further chemical abundance study. In the present work, we carry out a far-ultraviolet spectral analysis of the extreme SU UMa dwarf nova TU Men and the U Gem dwarf nova SS Aur using archival spectra. We derive the mass and temperature of the WD using the recently available DR2 Gaia parallaxes. The analysis of HST STIS spectra yields a WD mass ${M}_{\mathrm{wd}}={0.77}_{-0.13}^{+0.16}{M}_{\odot }$ with a temperature of 27,750 ± 1000 K for TU Men and a WD mass M<SUB>wd</SUB> ∼ 0.80 ± 0.15 M<SUB>⊙</SUB> with a temperature of ∼30,000 ± 1000 K for SS Aur. However, the analysis of a FUSE spectrum for SS Aur gives a higher temperature of ∼33,375 ± 1875 K, yielding a higher WD mass of ∼1 ± 0.25 M<SUB>⊙</SUB>, which could be due to the effect of a second hot emitting component present in the short wavelengths of FUSE. Most importantly, based on the white dwarf far-ultraviolet absorption lines, we find that both systems have subsolar carbon and silicon abundances. For TU Men, we also find suprasolar nitrogen abundance, evidence of CNO processing. <SUP>*</SUP> Based on observations made with the NASA/ESA Hubble Space Telescope, obtained from the data archive at the Space Telescope Science Institute. STScI is operated by the Association of University for Research in Astronomy, Inc. under NASA contract NAS 5-26555. | [
1799,
203,
418,
1645,
1732
] | [
"white dwarf stars",
"cataclysmic variable stars",
"dwarf novae",
"su ursae majoris stars",
"u geminorum stars"
] |
2022AJ....163..284H | The unpopular Package: A Data-driven Approach to Detrending TESS Full-frame Image Light Curves | The majority of observed pixels on the Transiting Exoplanet Survey Satellite (TESS) are delivered in the form of full-frame images (FFIs). However, the FFIs contain systematic effects such as pointing jitter and scattered light from the Earth and Moon that must be removed (i.e., "detrended") before downstream analysis. We present unpopular, an open-source Python package to obtain detrended TESS FFI light curves optimized for variable sources. The unpopular package implements a variant of the causal pixel model to remove systematics and allows for simultaneous fitting with a polynomial component to capture nontransit astrophysical variations, such as supernova signals or stellar variability, that tend to be removed in techniques optimized for exoplanet detection. We validate our method by detrending different sources (e.g., supernovae, tidal disruption events (TDEs), exoplanet-hosting stars, fast-rotating stars) and comparing our light curves to those obtained by other pipelines when appropriate. Our supernova and TDE light curves are visually similar to those obtained by others using the ISIS image subtraction package, indicating that unpopular can be used to extract multisector light curves by preserving astrophysical signals on timescales of a TESS sector (~27 days). We note that our method contains tuning parameters that are currently set heuristically, and that the optimal set of tuning parameters will likely depend on the particular signal the user is interested in obtaining. The unpopular source code and tutorials are freely available online. | [
1858,
1945,
918,
2109,
1916,
1851,
1761,
486,
1709
] | [
"astronomy data analysis",
"linear regression",
"light curves",
"time domain astronomy",
"time series analysis",
"transient sources",
"variable stars",
"exoplanet astronomy",
"transit photometry"
] |
2021AJ....162...10D | The High-energy Spectrum of the Nearby Planet-hosting Inactive Mid-M Dwarf LHS 3844 | To fully characterize the atmospheres, or lack thereof, of terrestrial exoplanets, we must include the high-energy environments provided by their host stars. The nearby mid-M dwarf LHS 3844 hosts a terrestrial world that lacks a substantial atmosphere. We present a time-series UV spectrum of LHS 3844 from 1131 to 3215 Å captured by HST/COS. We detect one flare in the FUV that has an absolute energy of 8.96 ± 0.77 × 10<SUP>28</SUP> erg and an equivalent duration of 355 ± 31 s. We extract the flare and quiescent UV spectra separately. For each spectrum, we estimate the Lyα flux using correlations between UV line strengths. We use Swift-XRT to place an upper limit on the soft X-ray flux and construct a differential emission model to estimate flux that is obscured by the interstellar medium. We compare the differential emission model flux estimates in the XUV to other methods that rely on scaling from the Lyα, Si iv, and N v lines in the UV. The XUV, FUV, and NUV flux of LHS 3844 relative to its bolometric luminosity is log<SUB>10</SUB>(L<SUB>band</SUB>/L<SUB>Bol</SUB>) =-3.65, -4.16, and -4.48, respectively, for the quiescent state. These values agree with trends in high-energy flux as a function of stellar effective temperature found by the MUSCLES survey for a sample of early-M dwarfs. Many of the most spectroscopically accessible terrestrial exoplanets orbit inactive mid-to-late M dwarfs like LHS 3844. Measurements of M dwarf high-energy spectra are preferable for exoplanet characterization but are not always possible. The spectrum of LHS 3844 is a useful proxy for the current radiation environment for these worlds. | [
1736,
982,
487,
1603,
761,
1739,
1543
] | [
"ultraviolet astronomy",
"m dwarf stars",
"exoplanet atmospheres",
"stellar flares",
"hubble space telescope",
"ultraviolet observatories",
"space observatories"
] |
2020ApJ...905...46G | Retrieval of the d/sdL7+T7.5p Binary SDSS J1416+1348AB | We present the distance-calibrated spectral energy distribution (SED) of the d/sdL7 SDSS J14162408+1348263A (J1416A) and an updated SED for SDSS J14162408+1348263B (J1416B). We also present the first retrieval analysis of J1416A using the Brewster retrieval code base and the second retrieval of J1416B. We find that the primary is best fit by a nongray cloud opacity with a power-law wavelength dependence but is indistinguishable between the type of cloud parameterization. J1416B is best fit by a cloud-free model, consistent with the results from Line et al. Most fundamental parameters derived via SEDs and retrievals are consistent within 1σ for both J1416A and J1416B. The exceptions include the radius of J1416A, where the retrieved radius is smaller than the evolutionary model-based radius from the SED for the deck cloud model, and the bolometric luminosity, which is consistent within 2.5σ for both cloud models. The pair's metallicity and carbon-to-oxygen ratio point toward formation and evolution as a system. By comparing the retrieved alkali abundances while using two opacity models, we are able to evaluate how the opacities behave for the L and T dwarf. Lastly, we find that relatively small changes in composition can drive major observable differences for lower-temperature objects. | [
185,
896,
1680,
555
] | [
"brown dwarfs",
"l subdwarfs",
"t subdwarfs",
"fundamental parameters of stars"
] |
2020ApJS..247...11R | Radial Velocity Photon Limits for the Dwarf Stars of Spectral Classes F-M | The determination of extrasolar planet masses with the radial velocity (RV) technique requires spectroscopic Doppler information from the planet's host star, which varies with stellar brightness and temperature. We analyze the Doppler information in spectra from dwarfs of spectral types F-M utilizing empirical information from HARPS and CARMENES data and model spectra. We revisit the question of whether optical or near-infrared instruments are more efficient for RV observations in low-mass stars, and we come to the conclusion that an optical setup (BVR bands) is more efficient than a near-infrared one (YJHK) in dwarf stars hotter than 3200 K. We publish a catalog of 46,480 well-studied F-M dwarfs in the solar neighborhood, and we compare its distribution to more than 1 million stars from Gaia DR2. For all stars, we estimate the RV photon noise achievable in typical observations under the assumption of no activity jitter and slow rotation. We find that with an ESPRESSO-like instrument at an 8 m telescope, a photon noise limit of 10 cm s<SUP>-1</SUP> or lower can be reached in more than 280 stars in a 5 minute observation. At 4 m telescopes, a photon noise limit of 1 m s<SUP>-1</SUP> can be reached in a 10 minute exposure in approximately 10,000 predominantly Sun-like stars with a HARPS-like (optical) instrument. The same applies to ∼3000 stars for a red optical setup that covers the R and I bands and ∼700 stars for a near-infrared instrument. For the latter two, many of the targets are nearby M dwarfs. Finally, we identify targets in which Earth-mass planets within the liquid water habitable zone can cause RV amplitudes comparable to the RV photon noise. Assuming the same exposure times as above, we find that an ESPRESSO-like instrument can reach this limit for 1 M<SUB>⊕</SUB> planets in more than 1000 stars. The optical, red optical, and near-infrared configurations reach the limit for 2 M<SUB>⊕</SUB> planets in approximately 500, 700, and 200 stars, respectively. An online tool is provided to estimate the RV photon noise as a function of stellar temperature and brightness and wavelength coverage. | [
1332,
2096,
556,
876,
982,
498,
205
] | [
"radial velocity",
"high resolution spectroscopy",
"g dwarf stars",
"k dwarf stars",
"m dwarf stars",
"exoplanets",
"catalogs"
] |
2020ApJ...903...98H | Delivery of Pebbles from the Protoplanetary Disk into Circumplanetary Disks | Small bodies likely existed in the late stage of planet formation either as remnants of the planetesimal formation stage or as fragments of larger planetesimals. Recent studies suggest that they may have played an important role in the formation of regular satellites of giant planets, but their delivery process into the circumplanetary disk has been poorly understood. Using orbital integration that incorporates the gas flow around the planet obtained by hydrodynamic simulation, we examine delivery of small bodies in the protoplanetary disk into circumplanetary disks. We find that large bodies can be captured when they experience strong gas drag near the midplane of the circumplanetary disk, while particles with Stokes number near unity tend to settle toward the midplane of the protoplanetary disk and can be captured near the outer edge of the circumplanetary disk. On the other hand, small particles coupled to the gas can be delivered into the circumplanetary disk with the vertically accreting gas and are captured near the surface of the circumplanetary disk over a wide radial region, if they are sufficiently stirred off the midplane of the protoplanetary disk. However, if the turbulence in the protoplanetary disk is not sufficiently strong, delivery of small particles by such a mechanism would not be efficient. Also, gas depletion in the vicinity of the planet's orbit reduces the efficiency of the delivery. In these cases, larger bodies directly captured by gas drag from the circumplanetary disk would be the major building blocks of regular satellites. | [
1300,
492,
509,
627,
872,
1425
] | [
"protoplanetary disks",
"exoplanet formation",
"extrasolar gaseous giant planets",
"galilean satellites",
"jovian satellites",
"natural satellite formation"
] |
2024ApJ...962...34R | X-Ray Polarimetry as a Tool to Constrain Orbital Parameters in X-Ray Binaries | X-ray binary systems consist of a companion star and a compact object in close orbit. Thanks to their copious X-ray emission, these objects have been studied in detail using X-ray spectroscopy and timing. The inclination of these systems is a major uncertainty in the determination of the mass of the compact object using optical spectroscopic methods. In this paper, we present a new method to constrain the inclination of X-ray binaries, which is based on the modeling of the polarization of X-rays photons produced by a compact source and scattered off the companion star. We describe our method and explore the potential of this technique in the specific case of the low-mass X-ray binary GS 1826‑238 observed by the Imaging X-ray Polarimetry Explorer observatory. | [
1278,
1811,
939,
733,
154,
1175,
780
] | [
"polarimetry",
"x-ray binary stars",
"low-mass x-ray binary stars",
"high mass x-ray binary stars",
"binary stars",
"orbit determination",
"inclination"
] |
2024PSJ.....5..152L | Updated Catalog of Kepler Planet Candidates: Focus on Accuracy and Orbital Periods | We present a new catalog of Kepler planet candidates that prioritizes accuracy of planetary dispositions and properties over uniformity. This catalog contains 4376 transiting planet candidates, including 1791 residing within 709 multiplanet systems, and provides the best parameters available for a large sample of Kepler planet candidates. We also provide a second set of stellar and planetary properties for transiting candidates that are uniformly derived for use in occurrence rate studies. Estimates of orbital periods have been improved, but as in previous catalogs, our tabulated values for period uncertainties do not fully account for transit timing variations (TTVs). We show that many planets are likely to have TTVs with long periodicities caused by various processes, including orbital precession, and that such TTVs imply that ephemerides of Kepler planets are not as accurate on multidecadal timescales as predicted by the small formal errors (typically 1 part in 10<SUP>6</SUP> and rarely >10<SUP>‑5</SUP>) in the planets' measured mean orbital periods during the Kepler epoch. Analysis of normalized transit durations implies that eccentricities of planets are anticorrelated with the number of companion transiting planets. Our primary catalog lists all known Kepler planet candidates that orbit and transit only one star; for completeness, we also provide an abbreviated listing of the properties of the two dozen nontransiting planets that have been identified around stars that host transiting planets discovered by Kepler. | [
488,
490,
498,
1709,
1258
] | [
"exoplanet catalogs",
"exoplanet dynamics",
"exoplanets",
"transit photometry",
"planetary theory"
] |
2020ApJ...892..120H | Cascade Model for Planetesimal Formation by Turbulent Clustering | We use a newly developed cascade model of turbulent concentration of particles in protoplanetary nebulae to calculate several properties of interest to the formation of primitive planetesimals and to the meteorite record. The model follows, and corrects, calculations of the primary initial mass function (IMF) of planetesimals by Cuzzi et al., in which an incorrect cascade model was used. Here we use the model of Hartlep et al., which has been validated against several published numerical simulations of particle concentration in turbulence. We find that, for a range of nebula and particle properties, planetesimals may be "born big," formed as sandpiles with diameters in the range 10-100 km, directly from freely floating particles. The IMFs have a modal nature, with a well-defined peak rather than a power-law size dependence. Predictions for the inner and outer parts of the nebula behave similarly in this regard, and observations of primitive bodies in the inner and outer nebula support such modal IMFs. Also, we present predictions of local particle concentrations on several lengthscales in which particles "commonly" find themselves, which have significance for meteoritical observations of the redox state and isotopic fractionation in regions of chondrule formation. An important difference between these results and those of Cuzzi et al. is that particle growth by sticking must proceed to a radius range of at least one to a few centimeters for the IMF and meteoritical properties to be most plausibly satisfied. That is, as far as the inner nebula goes, the predominant "particles" must be aggregates of chondrules (or chondrule-size precursors) rather than individual chondrules themselves. | [
1301,
1259,
1257,
1300,
229
] | [
"protoplanetary nebulae",
"planetesimals",
"planetary system formation",
"protoplanetary disks",
"chondrules"
] |
2023ApJ...943..133F | A Preferential Growth Channel for Supermassive Black Holes in Elliptical Galaxies at z ≲ 2 | The assembly of stellar and supermassive black hole (SMBH) mass in elliptical galaxies since z ~ 1 can help to diagnose the origins of locally observed correlations between SMBH mass and stellar mass. We therefore construct three samples of elliptical galaxies, one at z ~ 0 and two at 0.7 ≲ z ≲ 2.5, and quantify their relative positions in the M <SUB>BH</SUB>-M <SUB>*</SUB> plane. Using a Bayesian analysis framework, we find evidence for translational offsets in both stellar mass and SMBH mass between the local sample and both higher-redshift samples. The offsets in stellar mass are small, and consistent with measurement bias, but the offsets in SMBH mass are much larger, reaching a factor of 7 between z ~ 1 and z ~ 0. The magnitude of the SMBH offset may also depend on redshift, reaching a factor of ~20 at z ~ 2. The result is robust against variation in the high- and low-redshift samples and changes in the analysis approach. The magnitude and redshift evolution of the offset are challenging to explain in terms of selection and measurement biases. We conclude that either there is a physical mechanism that preferentially grows SMBHs in elliptical galaxies at z ≲ 2, or that selection and measurement biases are both underestimated, and depend on redshift. | [
651,
594,
1663
] | [
"giant elliptical galaxies",
"galaxy evolution",
"supermassive black holes"
] |
2023ApJ...946...89M | Jitter Mechanism as a Kind of Coherent Radiation: Constrained by the GRB 221009A Emission at 18 TeV | The emission of gamma-ray burst (GRB) 221009A at 18 TeV has been detected by the large high-altitude air shower observatory. We suggest jitter radiation as a possible explanation for the TeV emission for this energetic GRB. In our scenario, the radiation field is linked to the perturbation field, and the perturbation field is dominated by kinetic turbulence. Kinetic turbulence takes a vital role in both magnetic field generation and particle acceleration. The jitter radiation can reach the TeV energy band when we consider either electron cooling or Landau damping. We further suggest that the jitter radiation in the very high-energy band is coherent emission. Our modeling results can be constrained by the observational results of GRB 221009A in the TeV energy band. This radiation mechanism is expected to have wide applications in the high-energy astrophysical research field. | [
629,
739,
2055,
321,
994,
1261
] | [
"gamma-ray bursts",
"high energy astrophysics",
"radiative processes",
"cosmic magnetic fields theory",
"magnetic fields",
"plasma astrophysics"
] |
2023ApJ...951..148N | Search for Young and Intermediate-age Stellar Populations in the Galactic Center with Subaru/MOIRCS and CO Narrowband Filters | Extinction toward the Galactic Center (GC) is extreme and limits observations of its stars to the infrared. In addition, the extinction varies on scales of arcseconds. It is therefore highly challenging to distinguish between different stars photometrically and to identify young, massive, or intermediate-age stars that can trace recent star formation. Here we report the results of near-infrared imaging observations of a $6\buildrel{\,\prime}\over{.} 0\times 3\buildrel{\,\prime}\over{.} 3$ region at the GC that encompasses the northwest part of the nuclear star cluster and parts of the nuclear stellar disk. We carried out the observations with the wide-field camera MOIRCS of the Subaru Telescope, using three narrowband (NB) filters. Two of the filters trace the stellar continuum, while we use the third one to measure the strength of the CO absorption features that are prominent in the spectra of cool giants, shallower in the spectra of warmer stars, and absent in young massive stars. Thus, we aim to distinguish between old late-type giants and young and intermediate-age stars. We have found 131 candidates of young and intermediate-age stars. The magnitude limit is ≈11.25 in the extinction-corrected K-band magnitude. The contamination of the candidates by old giants is estimated to be 26%. We show that our method allows us to identify correctly four out of five spectroscopically confirmed massive stars, and 68 of 75 spectroscopically confirmed cool stars (91%). Our results suggest that imaging observations with a CO NB filter can be complementary to other methods to identify massive stars in the GC. | [
565,
792,
1088
] | [
"galactic center",
"infrared photometry",
"narrow band photometry"
] |
2021ApJ...910..139R | Quantifying Feedback from Narrow Line Region Outflows in Nearby Active Galaxies. III. Results for the Seyfert 2 Galaxies Markarian 3, Markarian 78, and NGC 1068 | Outflows of ionized gas driven by active galactic nuclei (AGN) may significantly impact the evolution of their host galaxies. However, determining the energetics of these outflows is difficult with spatially unresolved observations that are subject to strong global selection effects. We present part of an ongoing study using Hubble Space Telescope and Apache Point Observatory spectroscopy and imaging to derive spatially resolved mass outflow rates and energetics for narrow-line region outflows in nearby AGN that are based on multi-component photoionization models to account for spatial variations in gas ionization, density, abundances, and dust content. This expanded analysis adds Mrk 3, Mrk 78, and NGC 1068, doubling our earlier sample. We find that the outflows contain total ionized gas masses of M ≈ 10<SUP>5.5</SUP>-10<SUP>7.5</SUP> M<SUB>⊙</SUB> and reach peak velocities of v ≈ 800-2000 km s<SUP>-1</SUP>. The outflows reach maximum mass outflow rates of ${\dot{M}}_{\mathrm{out}}\approx 3\mbox{--}12\,{M}_{\odot }$ <!-- --> yr<SUP>-1</SUP> and encompass total kinetic energies of E ≈ 10<SUP>54</SUP>-10<SUP>56</SUP> erg. The outflows extend to radial distances of r ≈ 0.1-3 kpc from the nucleus, with the gas masses, outflow energetics, and radial extents positively correlated with AGN luminosity. The outflow rates are consistent with in situ ionization and acceleration where gas is radiatively driven at multiple radii. These radial variations indicate that spatially resolved observations are essential for localizing AGN feedback and determining the most accurate outflow parameters. <SUP>*</SUP> Based on observations made with the NASA/ESA Hubble Space Telescope, obtained from the Data Archive at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. These observations are associated with program Nos. 5140, 5754, 7404, 7573, and 8480. <SUP>†</SUP> Based in part on observations obtained with the Apache Point Observatory 3.5 m telescope, which is owned and operated by the Astrophysical Research Consortium. | [
17,
16,
2017,
459,
1447,
1006,
1663,
602,
626,
848
] | [
"active galaxies",
"active galactic nuclei",
"agn host galaxies",
"emission line galaxies",
"seyfert galaxies",
"markarian galaxies",
"supermassive black holes",
"galaxy kinematics",
"galaxy winds",
"interstellar medium wind"
] |
2021AJ....162..186B | orvara: An Efficient Code to Fit Orbits Using Radial Velocity, Absolute, and/or Relative Astrometry | We present an open-source Python package, Orbits from Radial Velocity, Absolute, and/or Relative Astrometry (orvara), to fit Keplerian orbits to any combination of radial velocity, relative astrometry, and absolute astrometry data from the Hipparcos-Gaia Catalog of Accelerations. By combining these three data types, one can measure precise masses and sometimes orbital parameters even when the observations cover a small fraction of an orbit. The computational performance of orvara is achieved with an eccentric anomaly solver 5-10 times faster than commonly used approaches and low-level memory management to avoid Python overheads and by analytically marginalizing out parallax, barycenter proper motion, and instrument-specific radial velocity zero-points. Through its integration with the Hipparcos and Gaia intermediate astrometry package htof, orvara can properly account for the epoch astrometry measurements of Hipparcos and the measurement times and scan angles of individual Gaia epochs. We configure orvara with modifiable .ini configuration files tailored to any specific stellar or planetary system. We demonstrate orvara with a case study application to a recently discovered white dwarf/main-sequence system, HD 159062. By adding absolute astrometry to literature radial velocity and relative astrometry data, our comprehensive Markov Chain Monte Carlo analysis improves the precision of HD 159062B's mass by more than an order of magnitude to {0.6083}_{-0.0073}^{+0.0083}$ M<SUB>⊙</SUB>. We also derive a low eccentricity and large semimajor axis, establishing HD 159062AB as a system that did not experience Roche lobe overflow. | [
1175,
884,
1855,
486,
2130,
1332
] | [
"orbit determination",
"keplerian orbit",
"astronomy software",
"exoplanet astronomy",
"astrometric exoplanet detection",
"radial velocity"
] |
2022ApJ...935L...9B | Stars That Approach within One Parsec of the Sun: New and More Accurate Encounters Identified in Gaia Data Release 3 | Close encounters of stars to the Sun could affect life on Earth through gravitational perturbations of comets in the Oort cloud or exposure to ionizing radiation. By integrating orbits through the Galactic potential, I identify which of 33 million stars in Gaia DR3 with complete phase space information come close to the Sun. 61 stars formally approach within 1 pc, although there is high confidence in only 42 (two thirds) of these, the rest being spurious measurements or (in) binary systems. Most of the stars will encounter within the past or future 6 Myr; earlier/later encounters are less common due to the magnitude limit of the Gaia radial velocities (RVs). Several close encountering stars are identified for the first time, and the encounter times, distances, and velocities of previously known close encounters are determined more precisely on account of the significantly improved precision of Gaia DR3 over earlier releases. The K7 dwarf Gl 710 remains the closest known encounter, with an estimated (median) encounter distance of 0.0636 pc (90% confidence interval 0.0595-0.0678 pc) to take place in 1.3 Myr. The new second closest encounter took place 2.8 Myr ago: this was the G3 dwarf HD 7977, now 76 pc away, which approached within less than 0.05 pc of the Sun with a probability of one third. The apparent close encounter of the white dwarf UPM J0812-3529 is probably spurious due to an incorrect RV in Gaia DR3. | [
1541,
1509
] | [
"space astrometry",
"solar neighborhood"
] |
2022ApJ...935..158P | Exploring Refractory Organics in Extraterrestrial Particles | The origin of organic compounds detected in meteorites and comets, some of which could have served as precursors of life on Earth, remains an open question. The aim of the present study is to make one more step in revealing the nature and composition of organic materials of extraterrestrial particles by comparing infrared spectra of laboratory-made refractory organic residues to spectra of cometary particles returned by the Stardust mission, interplanetary dust particles, and meteorites. Our results reinforce the idea of a pathway for the formation of refractory organics through energetic and thermal processing of molecular ices in the solar nebula. There is also the possibility that some of the organic material had formed already in the parental molecular cloud before it entered the solar nebula. The majority of the IR "organic" bands of the studied extraterrestrial particles can be reproduced in the spectra of the laboratory organic residues. We confirm the detection of water, nitriles, hydrocarbons, and carbonates in extraterrestrial particles and link it to the formation location of the particles in the outer regions of the solar nebula. To clarify the genesis of the species, high-sensitivity observations in combination with laboratory measurements like those presented in this paper are needed. Thus, this study presents one more piece of the puzzle of the origin of water and organic compounds on Earth and motivation for future collaborative laboratory and observational projects. | [
75,
1528,
2004,
1037,
2203
] | [
"astrochemistry",
"solar system",
"laboratory astrophysics",
"meteorite composition",
"comet origins"
] |
2020ApJ...890...66K | Are Faint Supernovae Responsible for Carbon-enhanced Metal-poor Stars? | Mixing and fallback models in faint supernova models are supposed to reproduce the abundance patterns of observed carbon-enhanced metal-poor (CEMP) stars in the Galactic halo. A fine-tuning of the model parameters for individual stars is required to reproduce the observed ratios of carbon to iron. We focus on extremely metal-poor stars formed out of the ejecta from the mixing and fallback models using a chemical evolution model. Our chemical evolution models take into account the contribution of individual stars to chemical enrichment in host halos, together with their evolution in the context of the hierarchical clustering. Parameterized models of mixing and fallback models for Population III faint supernovae are implemented in the chemical evolution models with merger trees to reproduce the observed CEMP stars. A variety of choices for model parameters on star formation and metal pollution by faint supernovae are unable to reproduce the observed stars with $[\mathrm{Fe}/{\rm{H}}]\lesssim -4$ and $[{\rm{C}}/{\rm{H}}]\gtrsim -2$ , which are the majority of CEMP stars among the lowest-metallicity stars. Only possible solution is to form stars from small ejecta mass, which produces an inconsistent metallicity distribution function. We conclude that not all the CEMP stars are explicable by the mixing and fallback models. We also tested the contribution of binary mass transfers from AGB stars that are also supposed to reproduce the abundances of known CEMP stars. This model reasonably reproduces the distribution of carbon and iron abundances simultaneously only if we assume that long-period binaries are favored at $[\mathrm{Fe}/{\rm{H}}]\lesssim -3.5$ . | [
580,
225,
699,
1284,
1285
] | [
"galaxy chemical evolution",
"chemical enrichment",
"halo stars",
"population ii stars",
"population iii stars"
] |
2022ApJ...935..120J | Reconstructing the Assembly of Massive Galaxies. I. The Importance of the Progenitor Effect in the Observed Properties of Quiescent Galaxies at z ≈ 2 | We study the relationship between the morphology and star formation history (SFH) of 361 quiescent galaxies (QGs) at redshift <z <SUB>obs</SUB>> ≈ 2, with stellar mass $\mathrm{log}{M}_{* }\geqslant 10.3$ , selected with the UVJ technique. Taking advantage of panchromatic photometry covering the rest-frame UV-to-NIR spectral range ( ≈40 bands), we reconstruct the nonparametric SFH of the galaxies with the fully Bayesian SED fitting code PROSPECTOR. We find that the half-light radius R <SUB> e </SUB>, observed at z <SUB>obs</SUB>, depends on the formation redshift of the galaxies, z <SUB>form</SUB>, and that this relationship depends on M <SUB>*</SUB>. At $\mathrm{log}{M}_{* }\lt 11$ , the relationship is consistent with ${R}_{e}\propto {\left(1+{z}_{\mathrm{form}}\right)}^{-1}$ , in line with the expectation that the galaxies' central density depends on the cosmic density at the time of their formation, i.e., the "progenitor effect." At $\mathrm{log}{M}_{* }\gt 11$ , the relationship between R <SUB> e </SUB> and z <SUB>form</SUB> flattens, suggesting that mergers become increasingly important for the size growth of more massive galaxies after they quenched. We also find that the relationship between z <SUB>form</SUB> and galaxy compactness similarly depends on M <SUB>*</SUB>. While no clear trend is observed for QGs with $\mathrm{log}{M}_{* }\gt 11$ , lower-mass QGs that formed earlier, i.e., with larger z <SUB>form</SUB>, have larger central stellar-mass surface densities, both within the R <SUB> e </SUB> (Σ<SUB> e </SUB>) and central 1 kpc (Σ<SUB>1 kpc</SUB>), and also larger M <SUB>1 kpc</SUB>/M <SUB>*</SUB>, the fractional mass within the central 1 kpc. These trends between z <SUB>form</SUB> and compactness, however, essentially disappear if the progenitor effect is removed by normalizing the stellar density with the cosmic density at z <SUB>form</SUB>. Our findings highlight the importance of reconstructing the SFH of galaxies before attempting to infer their intrinsic structural evolution. | [
59,
594,
622,
734,
2016
] | [
"apparent magnitude",
"galaxy evolution",
"galaxy structure",
"high-redshift galaxies",
"quenched galaxies"
] |
2024ApJ...964..173R | Accretion Disk Size and Updated Time-delay Measurements in the Gravitationally Lensed Quasar SDSS J165043.44+425149.3 | We analyze variability in 15-season optical lightcurves from the doubly imaged lensed quasar SDSS J165043.44+425149.3 (SDSS1650), comprising five seasons of monitoring data from the Maidanak Observatory (277 nights in total, including the two seasons of data previously presented in Vuissoz et al.), five seasons of overlapping data from the Mercator telescope (269 nights), and 12 seasons of monitoring data from the US Naval Observatory, Flagstaff Station at lower cadence (80 nights). We update the 2007 time-delay measurement for SDSS1650 with these new data, finding a time delay of ${\rm{\Delta }}{t}_{\mathrm{AB}}=-{55.1}_{-3.7}^{+4.0}$ days, with image A leading image B. We analyze the microlensing variability in these lightcurves using a Bayesian Monte Carlo technique to yield measurements of the size of the accretion disk at λ <SUB>rest</SUB> = 2420 Å, finding a half-light radius of log(r <SUB>1/2</SUB>/cm) = ${16.19}_{-0.58}^{+0.38}$ assuming a 60° inclination angle. This result is unchanged if we model 30% flux contamination from the broad-line region. We use the width of the Mg II line in the existing Sloan Digital Sky Survey spectra to estimate the mass of this system's supermassive black hole, finding M <SUB>BH</SUB> = 2.47 × 10<SUP>9</SUP> M <SUB>⊙</SUB>. We confirm that the accretion disk size in this system, whose black hole mass is on the very high end of the M <SUB>BH</SUB> scale, is fully consistent with the existing quasar accretion disk size–black hole mass relation. | [
1318,
1319,
670,
672
] | [
"quasar microlensing",
"quasars",
"gravitational lensing",
"gravitational microlensing"
] |
2021ApJ...909..166H | Sunspot Observations at the Eimmart Observatory and in Its Neighborhood during the Late Maunder Minimum (1681-1718) | The Maunder Minimum (1645-1715; hereafter MM) is generally considered as the only grand minimum in the chronological coverage of telescopic sunspot observations. Characterized by scarce sunspot occurrences and their asymmetric concentrations in the southern solar hemisphere, the MM has frequently been associated with a special state of solar dynamo activity. As such, it is important to analyze contemporary observational records and improve our understanding of this peculiar interval, whereas the original records are frequently preserved in historical archives and can be difficult to access. In this study, we consult historical archives in the National Library of Russia, St. Petersburg, and analyze a series of sunspot observations conducted at the Eimmart Observatory from 1681 to 1709, which is the second-richest sunspot data set produced during the MM, following La Hire's series, among existing data sets. We have further extended our analyses to neighboring observations to extend our investigations up to 1718. We first analyze source documents and descriptions of observational instruments. Our analyses have significantly revised the existing data set, removed contaminations, and updated and labeled them as Eimmart Observatory (78 days), Altdorf Observatory (4 days), Hoffmann (22 days), and Wideburg (25 days). The revisions have updated the temporal coverage of the contemporary sunspot observations from 73.4% to 66.9% from 1677 to 1709. We have also derived the positions of the observed sunspot groups in comparison with contemporary observations. Our results indicate hemispheric asymmetry in the MM and recovery of sunspot groups in both hemispheres after 1716, supporting the common paradigm of the MM. | [
1015,
1650,
1651,
1652,
1475,
1473
] | [
"maunder minimum",
"sunspot cycle",
"sunspot groups",
"sunspot number",
"solar activity",
"solar-terrestrial interactions"
] |
2020ApJ...904..138S | Detection of 2-4 GHz Continuum Emission from ɛ Eridani | The nearby star ɛ Eridani has been a frequent target of radio surveys for stellar emission and extraterrestrial intelligence. Using deep 2-4 GHz observations with the Very Large Array, we have uncovered a 29 μJy compact, steady continuum radio source coincident with ɛ Eridani to within 0"06 (≲2σ; 0.2 au at the distance of the star). Combining our data with previous high-frequency continuum detections of ɛ Eridani, our observations reveal a spectral turnover at 6 GHz. We ascribe the 2-6 GHz emission to optically thick, thermal gyroresonance radiation from the stellar corona, with thermal free-free opacity likely becoming relevant at frequencies below 1 GHz. The steep spectral index (α ≃ 2) of the 2-6 GHz spectrum strongly disfavors its interpretation as stellar-wind-associated thermal bremsstrahlung (α ≃ 0.6). Attributing the entire observed 2-4 GHz flux density to thermal free-free wind emission, we thus derive a stringent upper limit of 3 × 10<SUP>-11</SUP> M<SUB>⊙</SUB> yr<SUP>-1</SUP> on the mass-loss rate from ɛ Eridani. Finally, we report the nondetection of flares in our data above a 5σ threshold of 95 μJy. Together with the optical nondetection of the most recent stellar maximum expected in 2019, our observations postulate a likely evolution of the internal dynamo of ɛ Eridani. | [
305,
878,
1340,
1584
] | [
"stellar coronae",
"k stars",
"radio continuum emission",
"stellar atmospheres"
] |
2021ApJ...921...59H | A Fast and Accurate Analytic Method of Calculating Galaxy Two-point Correlation Functions | We have developed a new analytic method to calculate the galaxy two-point correlation functions accurately and efficiently, applicable to surveys with finite, regular, and mask-free geometries. We have derived simple, accurate formulas of the normalized random-random pair counts RR as functions of the survey area dimensions. We have also suggested algorithms to compute the normalized data-random pair counts DR analytically. With all edge corrections fully accounted for analytically, our method computes RR and DR with perfect accuracy and zero variance in O(1) and O(N<SUB>g</SUB>) time, respectively. We test our method on a galaxy catalog from the Evolution and Assembly of GaLaxies and their Environments (EAGLE) simulation. Our method calculates RR + DR at a speed 3-6 orders of magnitude faster than the brute-force Monte Carlo method and 2.5 orders of magnitude faster than tree-based algorithms. For a galaxy catalog with 10 million data points in a cube, this reduces the computation time to under 1 minute on a laptop. Our analytic method is favored over the traditional Monte Carlo method whenever applicable. Some applications in the study of correlation functions and power spectra in cosmological simulations and galaxy surveys are discussed. However, we recognize that its applicability is very limited for realistic surveys with masks, irregular shapes, and/or weighted patterns. | [
1951,
902,
1883
] | [
"two-point correlation function",
"large-scale structure of the universe",
"algorithms"
] |
2024ApJ...964...62Z | Velocity Acoustic Oscillations on Cosmic Dawn 21 cm Power Spectrum as a Probe of Small-scale Density Fluctuations | We investigate the feasibility of using the velocity acoustic oscillations (VAO) features on the Cosmic Dawn 21 cm power spectrum to probe small-scale density fluctuations. In the standard cold dark matter (CDM) model, Population III stars form in minihalos and affect the 21 cm signal through Lyα and X-ray radiation. Such a process is modulated by the relative motion between dark matter and baryons, generating the VAO wiggles on the 21 cm power spectrum. In the fuzzy or warm dark matter models for which the number of minihalos is reduced, the VAO wiggles are weaker or even fully invisible. We investigate the wiggle features in the CDM with different astrophysical models and in different dark matter models. We find that (1) in the CDM model the relative streaming velocities can generate the VAO wiggles for broad ranges of parameters f <SUB>*</SUB>, ζ <SUB> X </SUB>, and f <SUB>esc,LW</SUB> ζ <SUB>LW</SUB>, though for different parameters the wiggles would appear at different redshifts and have different amplitudes. (2) For the axion model with m <SUB>a</SUB> ≲ 10<SUP>‑19</SUP> eV, the VAO wiggles are negligible. In the mixed model, the VAO signal is sensitive to the axion fraction. For example, the wiggles almost disappear when f <SUB>a</SUB> ≳ 10% for m <SUB>a</SUB> = 10<SUP>‑21</SUP> eV. Therefore, the VAO signal can be an effective indicator for small-scale density fluctuations and a useful probe of the nature of dark matter. The Square Kilometre Array-low with ∼2000 hr observation time has the ability to detect the VAO signal and constrain dark matter models. | [
1383,
690,
1285,
265,
1787,
902,
813
] | [
"reionization",
"h i line emission",
"population iii stars",
"cold dark matter",
"warm dark matter",
"large-scale structure of the universe",
"intergalactic medium"
] |
2023ApJS..268...32M | Powerful Radio Sources in the Southern Sky. II. A Swift X-Ray Perspective | We recently constructed the G4Jy-3CRE, a catalog of extragalactic radio sources based on the GLEAM 4-Jy (G4Jy) sample, with the aim of increasing the number of powerful radio galaxies and quasars with similar selection criteria to those of the revised release of the Third Cambridge Catalog (3CR). The G4Jy-3CRE consists of a total of 264 radio sources mainly visible from the Southern Hemisphere. Here, we present an initial X-ray analysis of 89 G4Jy-3CRE radio sources with archival X-ray observations from the Neil Gehrels Swift Observatory. We reduced a total of 624 Swift observations, for about 0.9 Ms of integrated exposure time. We found X-ray counterparts for 59 radio sources belonging to the G4Jy-3CRE, nine of them showing extended X-ray emission. The remaining 30 sources do not show any X-ray emission associated with their radio cores. Our analysis demonstrates that X-ray snapshot observations, even if lacking uniform exposure times, as those carried out with Swift, allow us to (i) verify and/or refine the host galaxy identification; (ii) discover the extended X-ray emission around radio galaxies of the intracluster medium when harbored in galaxy clusters, as the case of G4Jy 1518 and G4Jy 1664; and (iii) detect X-ray radiation arising from their radio lobes, as for G4Jy 1863. | [
2134,
1347,
1348,
1349,
584,
563,
1824,
1671
] | [
"radio active galactic nuclei",
"radio jets",
"radio lobes",
"radio loud quasars",
"galaxy clusters",
"galactic and extragalactic astronomy",
"x-ray surveys",
"surveys"
] |
2020AJ....160....9L | Speckle Holography of Visual Double Stars at the 2.1 m Telescope of OAN-SPM: First Results | We present our first results of multiband Speckle Holography of components of visual double stars. The observations were performed during 2019 April at the 2.1 m telescope at the Observatorio Astronómico Nacional at Sierra de San Pedro Mártir (México). We have observed 190 double stars with separation between 3″ and 5″. The position angle, separation and magnitude difference in three broadband optical filters (VRI) for these systems are provided. For 15 systems we found different interesting features, we have identified a close component for 9 of those systems; 5 of them are newly discovered. In the remaining 6 systems, although unresolved, we found elongations that we have been able to derive astrometric parameters if proven to be a (newly discovered) close component. This corresponds to about 8% of the sample presenting a certain feature in one of the components and about 5% of the sample having a confirmed close component. | [
154,
745,
1684
] | [
"binary stars",
"holographic interferometry",
"astronomical techniques"
] |
2020ApJ...891...60W | Theoretical Study of the State-resolved Thermal Rate Constants for the Astrophysical Reaction Li + HD<SUP>+</SUP> (V = 0, 1) | In the present study, we use the time-dependent wave packet (TDWP) method to calculate the thermal rate constants for the reaction Li + HD<SUP>+</SUP>(V = 0, 1) → LiH/LiD + H<SUP>+</SUP>/D<SUP>+</SUP> in the temperature range of 200-5000 K on the potential energy surface constructed by Martinazzo et al. Total rate constants for both the V = 0 and V = 1 reactions exhibit simple Arrhenius behavior and are compared with previous isotope reactions. Total rate constants for V = 1 are several times larger than those of V = 0, particularly in the low-temperature region. For the two channels of the reaction, the vibrational excitation of HD<SUP>+</SUP> greatly promotes the formation rate of the products LiH and LiD. For V = 0, the rate constants of LiH and LiD are comparable, while for V = 1, the rate constants of LiH are more than two times larger than those of LiD. The state-resolved rate constants show that the products LiH and LiD molecules can be excited to higher vibrational states and are preferably formed with hotter rotational states when the reactant HD<SUP>+</SUP> is vibrationally excited. Applications of these rate constants in the modeling of the astrophysical sources are discussed. | [
11,
435,
1365,
2107,
573
] | [
"abundance ratios",
"early universe",
"recombination (cosmology)",
"theoretical models",
"galaxies"
] |
2023ApJ...959L..13M | Auroras on Planets around Pulsars | The first extrasolar planets were discovered serendipitously, by finding the slight variation in otherwise highly regular timing of the pulses, caused by the planets orbiting a millisecond pulsar. In analogy with the solar system planets, we predict the existence of aurora on planets around millisecond pulsars. We perform the first magnetohydrodynamic simulations of magnetospheric pulsar-planet interaction and estimate the radio emission from such systems. We find that the radio emission from aurora on pulsar planets could be observable with the current instruments. We provide parameters for such a detection, which would be the first radio detection of an extrasolar planet. In addition to probing the atmosphere of planets in such extreme conditions, of great interest is also the prospect of the first direct probe into the pulsar wind. | [
1304,
1964,
2192
] | [
"pulsar planets",
"magnetohydrodynamics",
"aurorae"
] |
2024PASP..136d7001W | Research on the Optimal Design of the High-stability Optical System for Atmospheric Spectra in Transit Observation | Capturing the characteristics of exoplanetary atmospheres (CEA) through transit spectroscopy (TS) holds profound implications for our understanding of planetary formation and evolution. However, TS, the method employed for detecting CEA, indirectly extracts these characteristics from the subtle variations in stellar spectra during the transit process, necessitating a high level of observational stability in optical instrumentation. To mitigate observational errors in spectral energy within the optical system, this dissertation delves into the optimal design of a high-stability optical system tailored for atmospheric spectra in transit observations. Initially, a theoretical model of transit signal-to-noise ratios (S/Ns) catered to the EAC retrievals is formulated based on transit observation strategies. Subsequently, the optimal parameters and design approach for the optical system are explored through an analysis of the optical factors influencing S/N. Leveraging an observation simulator for optical instruments, the detection feasibility of the optimized optical system for capturing CEA is validated. | [
1708,
1554,
794,
1857,
2021
] | [
"transit instruments",
"spectrometers",
"infrared telescopes",
"astronomical simulations",
"exoplanet atmospheric composition"
] |
2023ApJ...951..124K | MASTER OT J030227.28+191754.5: A Dwarf Nova at a Massive Oxygen-Neon White Dwarf System? | We present timing and spectral analysis results of the NICER and NuSTAR observations of the dwarf nova MASTER OT J030227.28+191754.5 during the 2021-2022 outburst. The soft X-ray component was found to be dominated by blackbody radiation with a temperature of ~30 eV and also showed prominent oxygen and neon emission lines. The blackbody luminosity exceeded 10<SUP>34</SUP> erg s<SUP>-1</SUP>, which is consistent with theoretical predictions, and then decreased more than an order of magnitude in 3.5 days. The inferred abundances of oxygen and neon in the optically thin coronal region surrounding the central white dwarf (WD) are several times higher than the respective solar values. Although inconclusive, the abundance enrichment may originate from the WD, indicating that it may be mainly composed of oxygen and neon. Assuming that the blackbody radiation comes from the belt-shaped boundary layer between the WD and the accretion disk, we estimated the WD radius to be (2.9 ± 1.1) × 10<SUP>8</SUP> cm, which corresponds to the WD mass range of 1.15-1.34 M <SUB>⊙</SUB>. If the accretion continues for another ~1 Gyr, the WD may experience an accretion-induced collapse into a neutron star and form a so-called black widow pulsar system. | [
418,
1822,
1579,
203,
1809
] | [
"dwarf novae",
"x-ray sources",
"stellar accretion disks",
"cataclysmic variable stars",
"wz sagittae stars"
] |
2021PSJ.....2...19P | Examination of Fragment Species in the Comae of Several Comets Using an Integral Field Unit Spectrograph | Spectra of the comae of four comets were obtained with an integral field unit spectrograph on the Harlan J. Smith Telescope at McDonald Observatory. The passband of the spectrograph permitted the observation of C<SUB>2</SUB>, C<SUB>3</SUB>, CH, CN, and NH<SUB>2</SUB> transitions for these comets. The classical Haser model was used to derive production rates for each observed species. The production rates obtained for the comets were also used to obtain mixing ratios relative to CN. The relative abundances with respect to CN obtained for these comets vary greatly, but are largely consistent with ranges established from prior comet chemistry surveys. The notable exception is 168P/Hergenrother, which the results suggest is extremely depleted in volatiles, even with respect to many other comets designated as volatile depleted in prior surveys. The results for comet Hergenrother add to a small, but growing, body of data suggesting that there may be a subgroup of carbon-chain-depleted Jupiter-family comets that are also depleted in ammonia. | [
280,
271,
2158,
2095
] | [
"comets",
"comae",
"neutral coma gases",
"molecular spectroscopy"
] |
2024ApJS..272...37J | Advancing Solar Energetic Particle Event Prediction through Survival Analysis and Cloud Computing. I. Kaplan–Meier Estimation and Cox Proportional Hazards Modeling | Solar energetic particles (SEPs) pose significant challenges to technology, astronaut health, and space missions. This initial paper in our two-part series undertakes a comprehensive analysis of the time to detection for SEPs, applying advanced statistical techniques and cloud-computing resources to deepen our understanding of SEP event probabilities over time. We employ a range of models encompassing nonparametric, semiparametric, and parametric approaches, such as the Kaplan–Meier estimator and Cox Proportional Hazards models. These are complemented by various distribution models—including exponential, Weibull, lognormal, and log-logistic distributions—to effectively tackle the challenges associated with "censored data," a common issue in survival analysis. Employing Amazon Web Services and Python's "lifelines" and "scikit-survival" libraries, we efficiently preprocess and analyze large data sets. This methodical approach not only enhances our current analysis, but also sets a robust statistical foundation for the development of predictive models, which will be the focus of the subsequent paper. In identifying the key determinants that affect the timing of SEP detection, we establish the vital features that will inform the machine-learning (ML) techniques explored in the second paper. There, we will utilize advanced ML models—such as survival trees and random survival forests—to evolve SEP event prediction capabilities. This research is committed to advancing space weather, strengthening the safety of space-borne technology, and safeguarding astronaut health. | [
2037,
711,
1491,
1496,
1970
] | [
"space weather",
"heliosphere",
"solar energetic particles",
"solar flares",
"cloud computing"
] |
2020AJ....160..274B | BD+14°3061: A Luminous Yellow Post-AGB Star in the Galactic Halo | I report the discovery that the ninth-mag Galactic-halo star BD+14°3061 is a member of the rare class of luminous metal-poor "yellow post-AGB" stars. Its Gaia DR2 parallax implies an absolute magnitude of M<SUB>V</SUB> = -3.44 ± 0.27, and it is a very high-velocity star moving in a retrograde Galactic orbit. BD+14°3061 is a field analog of the half-dozen yellow PAGB stars known in Galactic globular clusters, which have closely similar absolute magnitudes. These objects are the visually brightest members of old stellar populations; their apparently narrow luminosity function makes them potentially useful as Population II standard candles. The spectral-energy distribution of BD+14°3061 out to 22 μm shows no evidence for circumstellar dust. The star is a low-amplitude semiregular pulsating variable, with typical periods of 30-32 days. A radial-velocity study suggests that it is a spectroscopic binary with a period of 429.6 days, making it similar to known binary yellow PAGB stars such as HD 46703 and BD+39°4926. | [
2121,
481,
656,
1557,
1444
] | [
"post-asymptotic giant branch stars",
"evolved stars",
"globular star clusters",
"spectroscopic binary stars",
"semi-regular variable stars"
] |
Subsets and Splits