Sazuna/UAT_keywords huggingface dataset:
Galaxy and Mass Assembly: A Comparison between Galaxy-Galaxy Lens Searches in KiDS/GAMA. Strong gravitational lenses are a rare and instructive type of astronomical object. Identification has long relied on serendipity, but different strategies—such as mixed spectroscopy of multiple galaxies along the line of sight, machine-learning algorithms, and citizen science—have been employed to identify these objects as new imaging surveys become available. We report on the comparison between spectroscopic, machine-learning, and citizen-science identification of galaxy-galaxy lens candidates from independently constructed lens catalogs in the common survey area of the equatorial fields of the Galaxy and Mass Assembly survey. In these, we have the opportunity to compare high completeness spectroscopic identifications against high-fidelity imaging from the Kilo Degree Survey used for both machine-learning and citizen-science lens searches. We find that the three methods—spectroscopy, machine learning, and citizen science—identify 47, 47, and 13 candidates, respectively, in the 180 square degrees surveyed. These identifications barely overlap, with only two identified by both citizen science and machine learning. We have traced this discrepancy to inherent differences in the selection functions of each of the three methods, either within their parent samples (i.e., citizen science focuses on low redshift) or inherent to the method (i.e., machine learning is limited by its training sample and prefers well-separated features, while spectroscopy requires sufficient flux from lensed features to lie within the fiber). These differences manifest as separate samples in estimated Einstein radius, lens stellar mass, and lens redshift. The combined sample implies a lens candidate sky density of ∼0.59 deg-2 and can inform the construction of a training set spanning a wider mass-redshift space. A combined approach and refinement of automated searches would result in a more complete sample of galaxy-galaxy lens candidates for future surveys.

Keywords: Galaxy dark matter halos, Giant elliptical galaxies, Redshift surveys, Strong gravitational lensing
Revisiting the Architecture of the KOI-89 System. While high stellar obliquities observed in exoplanetary systems may be attributed to processes that tilt the planetary orbits, it is also possible that they reflect misalignments between protoplanetary disks and stellar spins. This latter hypothesis predicts the presence of coplanar multiplanetary systems misaligned with their central stars. Here we reevaluate the evidence of such an architecture that has been claimed for the KOI-89 system. An early-type star, KOI-89 has one validated transiting planet, KOI-89.01/Kepler-462b (period 84.7 days, radius 3.0 R⊕), and one transiting planet candidate, KOI-89.02 (period 207.6 days, radius 4.0 R⊕), where the latter exhibits transit timing variations (TTVs). A previous modeling of the stellar gravity-darkening effect in the transit light curves inferred a high stellar obliquity of ≈70°. We perform photodynamical modeling of the Kepler transit light curves and use the resulting constraints on the orbital configuration and transit times to update the gravity-darkened transit model. As a result, we find no firm evidence for the gravity-darkening effect in the transit shapes and conclude that stellar obliquity is not constrained by the data. Given the evidence for low orbital eccentricities from the dynamical analysis, the system architecture can thus be consistent with many other multitransiting systems with flat, near-circular orbits aligned with the stellar spin. We find that the TTVs imparted on its neighbor imply that KOI-89.01 has a mass ≳20 M⊕. This would render it one of the densest known sub-Neptunes, mostly composed of a solid core. Lower masses are possible if the TTVs are instead due to an unseen third planet.

Keywords: Exoplanet dynamics, Exoplanets, Exoplanet systems, Exoplanet astronomy, Exoplanet structure
High-resolution Spectra of Earth-like Planets Orbiting Red Giant Host Stars. In the near future we will have ground- and space-based telescopes that are designed to observe and characterize Earth-like planets. While attention is focused on exoplanets orbiting main-sequence stars, more than 150 exoplanets have already been detected orbiting red giants, opening the intriguing question of what rocky worlds orbiting in the habitable zone (HZ) of red giants would be like and how to characterize them. We present a high-resolution spectral database of reflection and emission spectra for nominal Earth-like planets orbiting in the red giant HZ from the visible to infrared (0.4-20 μm) for planets orbiting at the Earth-equivalent distance. We also show the change of such planetary spectra through the evolution of their red giant hosts. While the luminosity of the host increases the contrast ratio between star and planet, the increased orbital distance of the HZ for red giant hosts relaxes the light suppression requirements close to the star, which could make such planets interesting targets to characterize and search for signs of life, if new coronagraph designs with higher suppression at larger orbital separations could be developed. We assess the feasibility of characterizing atmospheric features including biosignatures for such planets with the proposed mission concept Large UV/Optical/IR Surveyor (LUVOIR).

Keywords: Horizontal branch, Evolved stars, Exoplanet evolution, Astrobiology, Red giant stars, Biosignatures, Habitable zone, Habitable planets, Exoplanet atmospheres, Stellar evolution
Mitigation of LEO Satellite Brightness and Trail Effects on the Rubin Observatory LSST. We report studies on the mitigation of optical effects of bright low-Earth-orbit (LEO) satellites on Vera C. Rubin Observatory and its Legacy Survey of Space and Time (LSST). These include options for pointing the telescope to avoid satellites, laboratory investigations of bright trails on the Rubin Observatory LSST camera sensors, algorithms for correcting image artifacts caused by bright trails, experiments on darkening SpaceX Starlink satellites, and ground-based follow-up observations. The original Starlink v0.9 satellites are g ∼ 4.5 mag, and the initial experiment "DarkSat" is g ∼ 6.1 mag. Future Starlink darkening plans may reach g ∼ 7 mag, a brightness level that enables nonlinear image artifact correction to well below background noise. However, the satellite trails will still exist at a signal-to-noise ratio ∼ 100, generating systematic errors that may impact data analysis and limit some science. For the Rubin Observatory 8.4 m mirror and a satellite at 550 km, the full width at half maximum of the trail is about 3″ as the result of an out-of-focus effect, which helps avoid saturation by decreasing the peak surface brightness of the trail. For 48,000 LEOsats of apparent magnitude 4.5, about 1% of pixels in LSST nautical twilight images would need to be masked.

Keywords: Observational astronomy, CCD observation, CCD photometry, Sky surveys, Astronomy data acquisition, Astronomy data analysis, Artificial satellites, Astronomical techniques, Field of view, Photometry, Astronomy data reduction
The Effect of Environment on AGN Activity: The Properties of Radio and Optical AGN in Void, Isolated, and Group Galaxies. The evolution of galaxies depends on their environment. In this work, active galactic nucleus (AGN) activity in different environments has been studied. The fractions of radio and optical AGN in four different environments have been compared using samples of void, isolated, group member, and the brightest group galaxies. Galaxies in voids show significantly lower stellar ages, concentrations, colors, and surface mass densities, and they experience more one-on-one interactions compared to the isolated galaxies and galaxies in groups. To study pure environmental effects, the biases caused by the stellar mass and galaxy type quantified by 4000 Šbreak strength have been removed. While the results confirm no dependence of the optical AGN activity on environment in blue galaxies and with lower significance in green galaxies, a higher fraction of optical AGN has been observed for the massive red galaxies in voids compared to the galaxies in dense environments. This may be related to the higher amount of one-on-one interaction observed in the void galaxies, or it may reflect more fundamental differences in the host galaxies or environments of the voids. The radio-mode AGN activity increases in the dense environment for red galaxies. No changes in the radio-loud AGN fraction have been observed for the blue and green galaxies. This shows that the effect of environment on AGN activity is not significant in the presence of cold gas in galaxies. We also discuss whether the efficiency of gas accretion depends on the properties of the host galaxy.

Keywords: AGN host galaxies, Active galaxies, Radio active galactic nuclei, Galaxy interactions
A Search for FeH in Hot-Jupiter Atmospheres with High-dispersion Spectroscopy. Most of the molecules detected thus far in exoplanet atmospheres, such as water and CO, are present for a large range of pressures and temperatures. In contrast, metal hydrides exist in much more specific regimes of parameter space, and so can be used as probes of atmospheric conditions. Iron hydride (FeH) is a dominant source of opacity in low-mass stars and brown dwarfs, and evidence for its existence in exoplanets has recently been observed at low resolution. We performed a systematic search of archival CARMENES near-infrared data for signatures of FeH during transits of 12 exoplanets. These planets span a large range of equilibrium temperatures (600 $\lesssim \,{T}_{\mathrm{eq}}\,\lesssim $ 4000 K) and surface gravities (2.5 $\lesssim \,\mathrm{log}g\,\lesssim $ 3.5). We did not find a statistically significant FeH signal in any of the atmospheres, but obtained potential low-confidence signals (signal-to-noise ratio ∼ 3) in two planets, WASP-33b and MASCARA-2b. Previous modeling of exoplanet atmospheres indicate that the highest volume mixing ratios (VMRs) of 10-7 to 10-9 are expected for temperatures between 1800 and 3000 K and log $g\gtrsim 3$ . The two planets for which we find low-confidence signals are in the regime where strong FeH absorption is expected. We performed injection and recovery tests for each planet and determined that FeH would be detected in every planet for VMRs $\geqslant {10}^{-6}$ , and could be detected in some planets for VMRs as low as ${10}^{-9.5}$ . Additional observations are necessary to conclusively detect FeH and assess its role in the temperature structures of hot-Jupiter atmospheres.

Keywords: High resolution spectroscopy, Exoplanet atmospheric composition , Hot Jupiters, Exoplanets, Exoplanet atmospheres
TOI 564 b and TOI 905 b: Grazing and Fully Transiting Hot Jupiters Discovered by TESS. We report the discovery and confirmation of two new hot Jupiters discovered by the Transiting Exoplanet Survey Satellite (TESS): TOI 564 b and TOI 905 b. The transits of these two planets were initially observed by TESS with orbital periods of 1.651 and 3.739 days, respectively. We conducted follow-up observations of each system from the ground, including photometry in multiple filters, speckle interferometry, and radial velocity measurements. For TOI 564 b, our global fitting revealed a classical hot Jupiter with a mass of ${1.463}_{-0.096}^{+0.10}$ MJ and a radius of ${1.02}_{-0.29}^{+0.71}$ RJ. Also a classical hot Jupiter, TOI 905 b has a mass of ${0.667}_{-0.041}^{+0.042}$ MJ and radius of ${1.171}_{-0.051}^{+0.053}$ RJ. Both planets orbit Sun-like, moderately bright, mid-G dwarf stars with V ∼ 11. While TOI 905 b fully transits its star, we found that TOI 564 b has a very high transit impact parameter of ${0.994}_{-0.049}^{+0.083}$ , making it one of only ∼20 known systems to exhibit a grazing transit and one of the brightest host stars among them. Therefore, TOI 564 b is one of the most attractive systems to search for additional nontransiting, smaller planets by exploiting the sensitivity of grazing transits to small changes in inclination and transit duration over a timescale of several years.

Keywords: Hot Jupiters, Radial velocity, Exoplanet astronomy, Exoplanet detection methods, Transit photometry, Extrasolar gaseous giant planets
ACCESS: Confirmation of No Potassium in the Atmosphere of WASP-31b. We present a new optical (400-950 nm) transmission spectrum of the hot Jupiter WASP-31b (M = 0.48 MJ; R = 1.54 RJ; P = 3.41 days), obtained by combining four transit observations. These transits were observed with IMACS on the Magellan Baade Telescope at Las Campanas Observatory as part of the ACCESS project. We investigate the presence of clouds/hazes in the upper atmosphere of this planet, as well as the contribution of stellar activity on the observed features. In addition, we search for absorption features of the alkali elements Na I and K I, with particular focus on K I, for which there have been two previously published disagreeing results. Observations with Hubble Space Telescope (HST)/STIS detected K I, whereas ground-based low- and high-resolution observations did not. We use equilibrium and nonequilibrium chemistry retrievals to explore the planetary and stellar parameter space of the system with our optical data combined with existing near-IR observations. Our best-fit model is that with a scattering slope consistent with a Rayleigh slope ( $\alpha ={5.3}_{-3.1}^{+2.9}$ ), high-altitude clouds at a log cloud top pressure of -3.6 ${}_{-2.1}^{+2.7}$ bars, and possible muted H2O features. We find that our observations support other ground-based claims of no K I. Clouds are likely why signals like H2O are extremely muted and Na or K cannot be detected. We then juxtapose our Magellan/IMACS transmission spectrum with existing VLT/FORS2, HST/WFC3, HST/STIS, and Spitzer observations to further constrain the optical-to-infrared atmospheric features of the planet. We find that a steeper scattering slope (α = 8.3 ± 1.5) is anchored by STIS wavelengths blueward of 400 nm and only the original STIS observations show significant potassium signal.

Keywords: Observational astronomy, Exoplanets, Hot Jupiters, Spectroscopy, Exoplanet atmospheres
JWST Noise Floor. I. Random Error Sources in JWST NIRCam Time Series. James Webb Space Telescope (JWST) transmission and emission spectra will provide invaluable glimpses of transiting exoplanet atmospheres, including possible biosignatures. This promising science from JWST, however, will require exquisite precision and understanding of systematic errors that can impact the time series of planets crossing in front of and behind their host stars. Here, we provide estimates of the random noise sources affecting JWST Near-Infrared Camera (NIRCam) time-series data on the integration-to-integration level. We find that 1/f noise can limit the precision of grism time series for two groups (230-1000 ppm depending on the extraction method and extraction parameters), but will average down like the square root of N frames/reads. The current NIRCam grism time-series mode is especially affected by 1/f noise because its GRISMR dispersion direction is parallel to the detector fast-read direction, but could be alleviated in the GRISMC direction. Care should be taken to include as many frames as possible per visit to reduce this 1/f noise source: thus, we recommend the smallest detector subarray sizes one can tolerate, four output channels, and readout modes that minimize the number of skipped frames (RAPID or BRIGHT2). We also describe a covariance-weighting scheme that can significantly lower the contributions from 1/f noise as compared to sum extraction. We evaluate the noise introduced by pre-amplifier offsets, random telegraph noise, and high dark current resistor capacitor (RC) pixels and find that these are correctable below 10 ppm once background subtraction and pixel masking are performed. We explore systematic error sources in a companion paper.

Keywords: Transmission spectroscopy, Astronomical detectors, Astronomical techniques, Atomic spectroscopy, Spectroscopy, Photometry, Exoplanet atmospheres
The Great Inequality and the Dynamical Disintegration of the Outer Solar System. Using an ensemble of N-body simulations, this paper considers the fate of the outer gas giants (Jupiter, Saturn, Uranus, and Neptune) after the Sun leaves the main sequence and completes its stellar evolution. Due to solar mass loss—which is expected to remove roughly half of the star's mass—the orbits of the giant planets expand. This adiabatic process maintains the orbital period ratios, but the mutual interactions between planets and the width of mean-motion resonances (MMR) increase, leading to the capture of Jupiter and Saturn into a stable 5:2 resonant configuration. The expanded orbits, coupled with the large-amplitude librations of the critical MMR angle, make the system more susceptible to perturbations from stellar flyby interactions. Accordingly, within about 30 Gyr, stellar encounters perturb the planets onto the chaotic subdomain of the 5:2 resonance, triggering a large-scale instability, which culminates in the ejections of all but one planet over the subsequent ∼10 Gyr. After an additional ∼50 Gyr, a close stellar encounter (with a perihelion distance less than ∼200 au) liberates the final planet. Through this sequence of events, the characteristic timescale over which the solar system will be completely dissolved is roughly 100 Gyr. Our analysis thus indicates that the expected dynamical lifetime of the solar system is much longer than the current age of the universe, but is significantly shorter than previous estimates.

Keywords: Solar system, Dynamical evolution
WASP-117 b: An Eccentric Hot Saturn as a Future Complex Chemistry Laboratory. We present spectral analysis of the transiting Saturn-mass planet WASP-117 b, observed with the G141 grism of the Hubble Space Telescope's (HST) Wide Field Camera 3. We reduce and fit the extracted spectrum from the raw transmission data using the open-source software Iraclis before performing a fully Bayesian retrieval using the publicly available analysis suite TauREx 3.0. We detect water vapor alongside a layer of fully opaque cloud, retrieving a terminator temperature of ${T}_{\mathrm{term}}={833}_{-156}^{+260}$ K. In order to quantify the statistical significance of this detection, we employ the atmospheric detectability index (ADI), deriving a value of ADI = 2.30, which provides positive but not strong evidence against the flat-line model. Due to the eccentric orbit of WASP-117 b, it is likely that chemical and mixing timescales oscillate throughout orbit due to the changing temperature, possibly allowing warmer chemistry to remain visible as the planet begins transit, despite the proximity of its point of ingress to apastron. We present simulated spectra of the planet as would be observed by the future space missions such as the Atmospheric Remote-sensing Infrared Exoplanet Large-survey and the James Webb Space Telescope and show that, despite not being able to probe such chemistry with current HST data, these observatories should make it possible in the not too distant future.

Keywords: Radiative transfer simulations, Astronomy data analysis, Exoplanet atmospheres, Transmission spectroscopy
Time-variable Radio Recombination Line Emission in W49A. We present new Jansky Very Large Array (VLA) images of the central region of the W49A star-forming region at 3.6 cm and at 7 mm at resolutions of 0"15 (1650 au) and 0"04 (440 au), respectively. The 3.6 cm data reveal new morphological detail in the ultracompact H II region population, as well as several previously unknown and unresolved sources. In particular, source A shows elongated, edge-brightened bipolar lobes, indicative of a collimated outflow, and source E is resolved into three spherical components. We also present VLA observations of radio recombination lines at 3.6 cm and 7 mm, and IRAM Northern Extended Millimeter Array (NOEMA) observations at 1.2 mm. Three of the smallest ultracompact H II regions (sources A, B2, and G2) all show broad kinematic linewidths, with ΔVFWHM ≳ 40 km s-1. A multi-line analysis indicates that broad linewidths remain after correcting for pressure broadening effects, suggesting the presence of supersonic flows. Substantial changes in linewidth over the 21 yr time baseline at both 3.6 cm and 7 mm are found for source G2. At 3.6 cm, the linewidth of G2 changed from 31.7 ± 1.8 km s-1 to 55.6 ± 2.7 km s-1, an increase of +23.9 ± 3.4 km s-1. The G2 source was previously reported to have shown a 3.6 cm continuum flux density decrease of 40% between 1994 and 2015. This source sits near the center of a very young bipolar outflow whose variability may have produced these changes.

Keywords: Galactic radio sources, Compact H II region
TOI-481 b and TOI-892 b: Two Long-period Hot Jupiters from the Transiting Exoplanet Survey Satellite. We present the discovery of two new 10 day period giant planets from the Transiting Exoplanet Survey Satellite mission, whose masses were precisely determined using a wide diversity of ground-based facilities. TOI-481 b and TOI-892 b have similar radii (0.99 ± 0.01 ${R}_{{\rm{J}}}$ and 1.07 ± 0.02 ${R}_{{\rm{J}}}$ , respectively), and orbital periods (10.3311 days and 10.6266 days, respectively), but significantly different masses (1.53 ± 0.03 ${M}_{{\rm{J}}}$ versus 0.95 ± 0.07 ${M}_{{\rm{J}}}$ , respectively). Both planets orbit metal-rich stars ( $[\mathrm{Fe}/{\rm{H}}]$ = $+0.26\pm 0.05$ dex and $[\mathrm{Fe}/{\rm{H}}]$ = $+0.24\pm 0.05$ for TOI-481 and TOI-892, respectively) but at different evolutionary stages. TOI-481 is a ${M}_{\star }$ = 1.14 ± 0.02 ${M}_{\odot }$ , ${R}_{\star }$ = 1.66 ± 0.02 ${R}_{\odot }$ G-type star ( ${T}_{\mathrm{eff}}$ = $5735\pm 72$ K), that with an age of 6.7 Gyr, is in the turn-off point of the main sequence. TOI-892 on the other hand, is a F-type dwarf star ( ${T}_{\mathrm{eff}}$ = $6261\pm 80$ K), which has a mass of ${M}_{\star }$ = 1.28 ± 0.03 ${M}_{\odot }$ and a radius of ${R}_{\star }$ = 1.39 ± 0.02 ${R}_{\odot }$ . TOI-481 b and TOI-892 b join the scarcely populated region of transiting gas giants with orbital periods longer than 10 days, which is important to constrain theories of the formation and structure of hot Jupiters.

Keywords: Exoplanet astronomy, Exoplanet detection methods, Transit photometry, Radial velocity
Estimating Atmospheric Parameters of DA White Dwarf Stars with Deep Learning. The determination of atmospheric parameters of white dwarf stars (WDs) is crucial for researches on them. Traditional methodology is to fit the model spectra to observed absorption lines and report the parameters with the lowest χ2 error, which strongly relies on theoretical models that are not always publicly accessible. In this work, we construct a deep learning network to model-independently estimate ${T}_{\mathrm{eff}}$ and log g of DA stars (DAs), corresponding to WDs with hydrogen-dominated atmospheres. The network is directly trained and tested on the normalized flux pixels of full optical wavelength range of DAs spectroscopically confirmed in the Sloan Digital Sky Survey. Experiments in test yield that the rms error for ${T}_{\mathrm{eff}}$ and log g approaches 900 K and 0.1 dex, respectively. This technique is applicable for those DAs with ${T}_{\mathrm{eff}}$ from 5000 to 40,000 K and log g from 7.0 to 9.0 dex. Furthermore, the applicability of this method is verified for the spectra with degraded resolution of ∼200. So it is also practical for the analysis of DAs that will be detected by the Chinese Space Station Telescope.

Keywords: Astronomy data analysis, DA stars, Spectroscopy