Sazuna/UAT_keywords huggingface dataset:
Observational Constraints on Close Binary Star Evolution. I. Putative Contact Binaries with Long Periods and High Mass Ratios. Evolutionary and structural models for contact binary stars make quantitative predictions about the distribution of systems in the mass ratio (q)-orbital period (P) plane. Specifically, contact binaries containing primaries with convective envelopes are predicted to be absent at mass ratios larger than a critical threshold that is a function of orbital period and total mass. We test this prediction by characterizing candidate contact binaries that appear to have mass ratios in violation of this threshold. We obtained quadrature-phase echelle spectra (R ≈ 31,000) for 18 close binaries (0.65 day &lt; P &lt; 2.00 days) in the Kepler field, from which we extracted radial velocity profiles for each system. Use of a joint Markov Chain Monte Carlo fitting routine on the Kepler light curves and the radial velocity profiles allows us to retrieve all fundamental system and component parameters. Of the 18 systems, only one is a contact binary, and both components likely have radiative-not convective-envelopes. The 17 remaining systems are detached binaries (eight) or semidetached binaries (four) with ellipsoidal variations, rotating variables (four), or pulsating variables (one). Therefore, none of the systems are in violation of the theoretical mass ratio thresholds for low-mass contact binaries. The 12 noncontact binaries follow a T 2/T 1-q relation significantly weaker than expected for main-sequence components, suggesting radiative heating of the secondaries. Most of the secondaries have radii larger than main-sequence expectations, a possible consequence of heating. Four secondaries fill their Roche lobes, while none of the primaries do, possibly indicating prior mass-ratio reversal.

Keywords: Multiple star evolution, Close binary stars, Stellar evolutionary models, Ellipsoidal variable stars, Stellar evolutionary tracks, Contact binary stars
TOI-199 b: A Well-characterized 100 day Transiting Warm Giant Planet with TTVs Seen from Antarctica. We present the spectroscopic confirmation and precise mass measurement of the warm giant planet TOI-199 b. This planet was first identified in TESS photometry and confirmed using ground-based photometry from ASTEP in Antarctica including a full 6.5 hr long transit, PEST, Hazelwood, and LCO; space photometry from NEOSSat; and radial velocities (RVs) from FEROS, HARPS, CORALIE, and CHIRON. Orbiting a late G-type star, TOI-199 b has a ${104.854}_{-0.002}^{+0.001}\,{\rm{day}}$ period, a mass of 0.17 ± 0.02 M J, and a radius of 0.810 ± 0.005 R J. It is the first warm exo-Saturn with a precisely determined mass and radius. The TESS and ASTEP transits show strong transit timing variations (TTVs), pointing to the existence of a second planet in the system. The joint analysis of the RVs and TTVs provides a unique solution for the nontransiting companion TOI-199 c, which has a period of ${273.69}_{-0.22}^{+0.26}\,{\rm{days}}$ and an estimated mass of ${0.28}_{-0.01}^{+0.02}\,{M}_{{\rm{J}}}$ . This period places it within the conservative habitable zone.

Keywords: Radial velocity, Exoplanet systems, Exoplanet astronomy, Transit timing variation method, Exoplanet detection methods, Transit photometry
Discerning Parallax Amplitude in Astrometric Microlensing. Gravitational microlensing is a powerful method for discovering isolated stellar-mass black holes (ISMBHs). These objects make long-duration microlensing events. To characterize these lensing objects by fully resolving the microlensing degeneracy, measurements of parallax and astrometric deflections are necessary. Microlensing events due to ISMBHs have considerable astrometric deflections but small parallax amplitudes, ${\pi }_{{\rm{E}}}\propto 1/\sqrt{{M}_{{\rm{l}}}}$ , where M l is the lens mass. We numerically investigate the possibility of inferring parallax amplitude from astrometric deflection in microlensing events due to ISMBHs. The parallax amplitude in astrometric deflections is proportional to the relative parallax π rel, which means that it (i) does not strongly depend on M l and (ii) increases in microlensing observations toward the Magellanic Clouds. We assume that these events will be potentially detected in upcoming microlensing surveys such as (1) the Roman observations of the Galactic bulge (GB) and (2) the LSST observations of the Large Magellanic Cloud (LMC) and that the Extremely Large Telescope (ELT) will follow up on them with one data point every 10 days. We evaluate the probability of inferring parallax amplitude from these observations by calculating the Fisher and covariance matrices. For the GB, the efficiencies for discerning parallax amplitudes with a relative error of &lt;4% through astrometric and photometric observations are 3.8% and 29.1%, respectively. For observations toward the LMC, these efficiencies are 41.1% and 23.0%, respectively. Measuring parallax amplitude through astrometric deflections is plausible in GB events with a lens distance of ≲2.7 kpc and in LMC halo lensing. By monitoring long-duration microlensing events, the ELT can detect astrometric deflections and their parallax-induced deviations.

Keywords: Annual microlensing parallax, Monte Carlo methods, Astrometric microlensing effect, Computational methods, Gravitational microlensing
Spectral Retrieval with JWST Photometric data: a Case Study for HIP 65426 b. Half of the JWST high-contrast imaging objects will only have photometric data as of Cycle 2. However, to better understand their atmospheric chemistry that informs formation origin, spectroscopic data are preferred. Using HIP 65426 b, we investigate to what extent planet properties and atmospheric chemical abundance can be retrieved with only JWST photometric data points (2.5-15.5 μm) in conjunction with ground-based archival low-resolution spectral data (1.0-2.3 μm). We find that the data is consistent with an atmosphere with solar metallicity and C/O ratios at 0.40 and 0.55. We rule out 10× solar metallicity and an atmosphere with C/O = 1.0. We also find strong evidence of silicate clouds but no sign of an enshrouding featureless dust extinction. This work offers guidance and cautionary tales on analyzing data in the absence of medium-to-high-resolution spectral data.

Keywords: Exoplanet atmospheric composition , Exoplanet atmospheres
New Insights on 30 Dor B Revealed by High-quality Multiwavelength Observations. The supernova remnant (SNR) 30 Dor B is associated with the H II region ionized by the OB association LH99. The complex interstellar environment has made it difficult to study the physical structure of this SNR. We have used Hubble Space Telescope Hα images to identify SNR shocks and deep Chandra X-ray observations to detect faint diffuse emission. We find that 30 Dor B hosts three zones with very different X-ray surface brightnesses and nebular kinematics that are characteristic of SNRs in different interstellar environments and/or evolutionary stages. The ASKAP 888 MHz map of 30 Dor B shows counterparts to all X-ray emission features except the faint halo. The ASKAP 888 and 1420 MHz observations are used to produce a spectral index map, but its interpretation is complicated by the background thermal emission and the pulsar PSR J0537-6910's flat spectral index. The stellar population in the vicinity of 30 Dor B indicates a continuous star formation in the past 8-10 Myr. The observed very massive stars in LH99 cannot be coeval with the progenitor of 30 Dor B's pulsar. Adopting the pulsar's spin-down timescale, 5000 yr, as the age of the SNR, the X-ray shell would be expanding at ~4000 km s-1 and the post-shock temperature would be 1-2 orders of magnitude higher than that indicated by the X-ray spectra. Thus, the bright central region of 30 Dor B and the X-ray shell requires two separate SN events, and the faint diffuse X-ray halo perhaps other older SN events.

Keywords: Supernova remnants, Large Magellanic Cloud, Magellanic Clouds, Interstellar medium
GJ 357 d: Potentially Habitable World or Agent of Chaos?. Multiplanet systems provide important laboratories for exploring dynamical interactions within the range of known exoplanetary system architectures. One such system is GJ 357, consisting of a low-mass host star and three orbiting planets, the outermost (planet d) of which does not transit but lies within the habitable zone (HZ) of the host star. The minimum mass of planet d causes its nature to be unknown, both in terms of whether it is truly terrestrial and if it is a candidate for harboring surface liquid water. Here, we use three sectors of photometry from the Transiting Exoplanet Survey Satellite to show that planets c and d do not transit the host star, and therefore may have masses higher than the derived minimum masses. We present the results for a suite of dynamical simulations that inject an Earth-mass planet within the HZ of the system for three different orbital and mass configurations of planet d. These results show that planet d, rather than being a potentially habitable planet, is likely a source of significant orbital instability for other potential terrestrial planets within the HZ. We find that relatively small eccentricities of planet d cause a majority of the HZ to be unstable for an Earth-mass planet. These results highlight the importance of dynamical stability for systems that are prioritized in the context of planetary habitability.

Keywords: Exoplanet dynamics, Exoplanets, Exoplanet systems, Orbital evolution, Exoplanet astronomy, Astrobiology, Habitable planets
A Search for Technosignatures Around 11,680 Stars with the Green Bank Telescope at 1.15-1.73 GHz. We conducted a search for narrowband radio signals over four observing sessions in 2020-2023 with the L-band receiver (1.15-1.73 GHz) of the 100 m diameter Green Bank Telescope. We pointed the telescope in the directions of 62 TESS Objects of Interest, capturing radio emissions from a total of ~11,680 stars and planetary systems in the ~9' beam of the telescope. All detections were either automatically rejected or visually inspected and confirmed to be of anthropogenic nature. We also quantified the end-to-end efficiency of radio SETI pipelines with a signal injection and recovery analysis. The UCLA SETI pipeline recovers 94.0% of the injected signals over the usable frequency range of the receiver and 98.7% of the injections when regions of dense radio frequency interference are excluded. In another pipeline that uses incoherent sums of 51 consecutive spectra, the recovery rate is ~15 times smaller at ~6%. The pipeline efficiency affects calculations of transmitter prevalence and SETI search volume. Accordingly, we developed an improved Drake figure of merit and a formalism to place upper limits on transmitter prevalence that take the pipeline efficiency and transmitter duty cycle into account. Based on our observations, we can state at the 95% confidence level that fewer than 6.6% of stars within 100 pc host a transmitter that is continuously transmitting a narrowband signal with an equivalent isotropic radiated power (EIRP) &gt; 1013 W. For stars within 20,000 ly, the fraction of stars with detectable transmitters (EIRP &gt; 5 × 1016 W) is at most 3 × 10-4. Finally, we showed that the UCLA SETI pipeline natively detects the signals detected with AI techniques by Ma et al.

Keywords: Exoplanets, Technosignatures, Astrobiology, Search for extraterrestrial intelligence, Radio astronomy, Milky Way Galaxy
Direct Simulation Monte Carlo Modeling of Ammonia in Comet C/2014 Q2 (Lovejoy). Ammonia (NH3), likely the most abundant nitrogen-bearing molecule in cometary ices followed by hydrogen cyanide, is believed to be stored in the nucleus predominantly as a parent ice. However, spatial profiles of NH3 observed in comet C/2014 Q2 (Lovejoy) in the near-infrared region are consistent with a distributed source contribution (Dello Russo et al. 2022). We developed the direct simulation Monte Carlo model of ammonia in cometary coma and applied it to comet C/2014 Q2 (Lovejoy). Results suggest that NH3 molecules in the coma of C/2014 Q2 (Lovejoy) can plausibly originate from a combination of parent molecules of NH3 in the coma and a NH3 nucleus source. We demonstrate that the parents of NH3 having photodissociation lifetimes of several hundreds of seconds or longer (at 1 au from the Sun) can explain the observed spatial profile of NH3 in comet C/2014 Q2 (Lovejoy). Even though ammonia salts are possible candidates for parents of NH3, some simple ammonium salts such as NH4CN or NH4Cl may dissociate thermally within very short lifetimes after sublimation from the nucleus, so the contribution from those ammonium salts may be indistinguishable from the nucleus source. The lack of experimental data on photoprocesses for potential NH3 parent molecules prevent us from identifying the origin of NH3 in comets. Experimental and theoretical studies of photodissociation/ionization reactions of potential NH3 parent molecules by the solar UV radiation field are encouraged for the future identification of NH3 parents in comets.

Keywords: Comet nuclei, Comet volatiles , Comae
Stability and Detectability of Exomoons Orbiting HIP 41378 f, a Temperate Jovian Planet with an Anomalously Low Apparent Density. Moons orbiting exoplanets ("exomoons") may hold clues about planet formation, migration, and habitability. In this work, we investigate the plausibility of exomoons orbiting the temperate (T eq = 294 K) giant (R = 9.2 R ⊕) planet HIP 41378 f, which has been shown to have a low apparent bulk density of 0.09 g cm-3 and a flat near-infrared transmission spectrum, hinting that it may possess circumplanetary rings. Given this planet's long orbital period (P ≈ 1.5 yr), it has been suggested that it may also host a large exomoon. Here, we analyze the orbital stability of a hypothetical exomoon with a satellite-to-planet mass ratio of 0.0123 orbiting HIP 41378 f. Combining a new software package, astroQTpy, with REBOUND and EqTide, we conduct a series of N-body and tidal migration simulations, demonstrating that satellites up to this size are largely stable against dynamical escape and collisions. We simulate the expected transit signal from this hypothetical exomoon and show that current transit observations likely cannot constrain the presence of exomoons orbiting HIP 41378 f, though future observations may be capable of detecting exomoons in other systems. Finally, we model the combined transmission spectrum of HIP 41378 f and a hypothetical moon with a low-metallicity atmosphere and show that the total effective spectrum would be contaminated at the ~10 ppm level. Our work not only demonstrates the feasibility of exomoons orbiting HIP 41378 f but also shows that large exomoons may be a source of uncertainty in future high-precision measurements of exoplanet systems.

Keywords: Exoplanet dynamics, Natural satellites (Extrasolar), Transits, Exoplanet systems, Transmission spectroscopy, Exoplanet astronomy, Exoplanet tides
Evidence That the Occurrence Rate of Hot Jupiters around Sun-like Stars Decreases with Stellar Age. We investigate how the occurrence rate of giant planets (minimum mass &gt; 0.3 M Jup) around Sun-like stars depends on the age, mass, and metallicity of their host stars. We develop a hierarchical Bayesian framework to infer the number of planets per star (NPPS) as a function of both planetary and stellar parameters. The framework fully takes into account the uncertainties in the latter by utilizing the posterior samples for the stellar parameters obtained by fitting stellar isochrone models to the spectroscopic parameters, Gaia DR3 parallaxes, and 2MASS K s-band magnitudes adopting a certain bookkeeping prior. We apply the framework to 46 Doppler giants found around a sample of 382 Sun-like stars from the California Legacy Survey catalog that publishes spectroscopic parameters and search completeness for all the surveyed stars. We find evidence that the NPPS of hot Jupiters (orbital period P = 1-10 days) decreases roughly in the latter half of the main sequence over the timescale of ${ \mathcal O }(\mathrm{Gyr})$ , while that of cold Jupiters (P = 1-10 yr) does not. Assuming that this decrease is real and caused by tidal orbital decay, the modified stellar tidal quality factor ${Q}_{\star }^{{\prime} }$ is implied to be ${ \mathcal O }({10}^{6})$ for a Sun-like main-sequence star orbited by a Jupiter-mass planet with P ≈ 3 days.

Keywords: Hot Jupiters, Exoplanets, Tidal disruption, Exoplanet astronomy, Exoplanet evolution
Star Photometry for DECam Legacy Survey and Sloan Digital Sky Survey Images Based on Convolutional Neural Networks. Flux is one of the most fundamental parameters in astrophysics, and aperture photometry and point-spread function (PSF) photometry are commonly used methods to obtain the flux. With the continuous development of astronomical equipment that has generated massive data, researchers have to find more effective methods to obtain stellar fluxes. However, current photometric software such as SExtractor are very sensitive to the configuration parameters and are difficult to configure. We propose a new photometric model based on deep learning called sf-convolutional neural network (CNN) to extract aperture fluxes and PSF fluxes. For the simulated data including 5727 stars, the experimental results show that sf-CNN can predict fluxes better than SExtractor. The mean absolute error (MAE) values of sf-CNN and SExtractor for predicting PSF fluxes are 0.0034 and 0.0134, respectively. On the 6293 mixed stars in DECam Legacy Survey Data Release (DR) 9, the MAE values of the predicted PSF fluxes are 0.0075 and 0.0177, respectively. The PSF accuracy of the sf-CNN model is significantly higher than that of SExtractor. Additionally, the MAE values of the predicted aperture fluxes on 6215 mixed stars and 1341 blends of stars in Sloan Digital Sky Survey DR 12 illustrate that the accuracy of sf-CNN is still the highest. Meanwhile, the results indicate that sf-CNN outperforms VGG16 and ResNet50. Furthermore, sf-CNN is 100-200 times faster than Photutils on RTX 3070 GPU and 20-40 times faster than Photutils on I7 12700 CPU. sf-CNN can calculate fluxes efficiently and accurately only by setting a few parameters and may thus become a fundamental tool for the era of big data in astronomy.

Keywords: Stellar photometry, CCD photometry, Fundamental parameters of stars, Convolutional neural networks, Surface photometry
A Study of Eight Visual-spectroscopic Southern Binaries Using Recent SOAR Observations. Speckle observations performed between 2019 and 2022 with the HRCam attached to the 4.1 m SOAR telescope (Cerro Pachón, Chile) permitted to improve visual orbits of the southern binaries WDS 01243-0655 (BU 1163), WDS 09275-5806 (CHR 240), WDS 12114-1647 (S 643 AaAb), WDS 13317-0219 (HDS 1895), WDS 15282-0921 (BAG 25 AaAb), WDS 17304-0104 (STF 2173), WDS 19598-0957 (HO 276), and WDS 21274-0701 (HDS 3053). All of them are spectroscopic binaries, of which six are SB2, so relevant information about their individual masses has been obtained. Moreover, comparison between different values of their parallaxes (orbital, dynamic, and ANAPAR, a color-dependent model suitable for binary systems attending to the exact locations of the components on the MS in the HR diagram) with those provided by Hipparcos and Gaia missions, along with comments for each binary are presented. The luminosity determination of the 16 components allowed us to estimate their approximate age and position on the HR diagram as well.

Keywords: Binary stars, Orbits, Stellar dynamics, Stellar parallax, Spectroscopic binary stars, Stellar astronomy, Stellar masses, Visual binary stars, Stellar evolutionary tracks, Orbit determination
The Cycles of Alpha Centauri: Double Dipping of AB. In mid-2023, the Sunlike dwarfs of nearby α Centauri (HD 128620 ("A"): G2 V; HD 128621 ("B"): K1 V; hereafter "AB") coincidentally both entered coronal (T ≈ 1-3 MK) low states in their long-term X-ray cycles, as captured by the Chandra Observatory and its High Resolution Camera (HRC-I). The assessment benefited from a sensitivity degradation model for HRC-I based on a "check star," the F subgiant Procyon (α Canis Minoris A; HD 61421: F5 IV-V), further validated by Hubble Space Telescope time series of the Fe XII 1241.985 Å and 1349.396 Å coronal forbidden lines (T ≈ 1.6 MK) of all three stars. The AB starspot-cycle periods noted previously, 19 and 8 yr, appear to be holding. These deviate substantially from the 11 yr solar example, despite only modest differences in the stellar properties. The new cycle-minimum L X/L BOL of α Cen A is similar to that of the previous minimum observed by Chandra in 2005-2010, and close to solar-MIN X-ray levels in 2009 and 2019, with implications for the "basal" coronal flux of low-activity early G stars. The recent α Cen B X-ray MIN is similar to that in 2016 but higher than an earlier one in 2007-2009. Significantly, the B X-ray minima (in L X/L BOL) are comparable to the solar Cycle 24 maximum, suggesting plentiful starspots at the B-cycle MIN (contrary to the solar case). Tangentially, the current AB low states favor Doppler-reflex detections of planets, as opposed to the coronal high states, when elevated chromospheric activity can add nuisance signals to radial velocity time series.

Keywords: Ultraviolet sources, Starspots, Solar cycle, Ultraviolet telescopes, Ultraviolet spectroscopy, X-ray telescopes, Single x-ray stars
Reading Between the Lines: Investigating the Ability of JWST to Identify Discerning Features in exoEarth and exoVenus Transmission Spectra. The success of the Transiting Exoplanet Survey Satellite mission has led to the discovery of an abundance of Venus Zone terrestrial planets that orbit relatively bright host stars. Atmospheric observations of these planets play a crucial role in understanding the evolutionary history of terrestrial planets, past habitable states, and the divergence of Venus and Earth climates. The transmission spectrum of a Venus-like exoplanet can be difficult to distinguish from that of an Earthlike exoplanet however, which could severely limit what can be learned from studying exoVenuses. In this work we further investigate differences in transmission between hypothetical exoEarths and exoVenuses, both with varying amounts of atmospheric carbon dioxide (CO2). The exoEarths and exoVenuses were modeled assuming they orbit TRAPPIST-1 on the runaway greenhouse boundary. We simulated James Webb Space Telescope Near-Infrared Spectrograph PRISM transit observations of both sets of planets between 0.6 and 5.2 μm, and quantified the detectability of major absorption features in their transmission spectra. The exoEarth spectra include several large methane (CH4) features that can be detected in as few as six transits. The CH4 feature at 3.4 μm is the optimal for feature for discerning an exoEarth from an exoVenus since it is easily detectable and does not overlap with CO2 features. The sulfur dioxide (SO2) feature at 4.0 μm is the best indicator of an exoVenus, but it is detectable in atmospheres with reduced CO2 abundance.

Keywords: Observational astronomy, Exoplanet atmospheric composition , Exoplanets, Venus, Transmission spectroscopy, Planetary science, Exoplanet atmospheres
A Census of the Most Luminous Stars. I. The Upper HR Diagram for the Large Magellanic Cloud. Spectral classification and multiwavelength photometry for the most luminous stars in the LMC has greatly increased due to several recent surveys for both the hottest and coolest members. Combining data from these spectroscopic and photometric surveys, we have created catalogs based on their spectral classifications of the different groups: the luminous O and B stars, the A-type supergiants, and the evolved yellow and red supergiants. We derive their stellar parameters based on spectroscopic characteristics, and discuss the problems with extinction in crowded fields and the role of binarity on selected stars. Based on these surveys, we present the upper HR diagram representative of the LMC massive star population greater than 20 M ⊙.

Keywords: Massive stars, Large Magellanic Cloud