Sazuna/UAT_keywords huggingface dataset:
Atmospheric Mass Loss from TOI-1259 A b, a Gas Giant Planet with a White Dwarf Companion. The lack of close-in Neptune-mass exoplanets evident in transit surveys has largely been attributed to either photoevaporative mass loss or high-eccentricity migration. To distinguish between these two possibilities, we investigate the origins of TOI-1259 A b, a Saturn-mass (0.4MJ, 1.0RJ) exoplanet lying along the upper edge of the Neptune desert. TOI-1259 A b's close-in (P = 3.48 days) orbit and low bulk density make the planet particularly vulnerable to photoevaporation. We studied the upper atmosphere of TOI-1259 A b using metastable helium 1083 nm transits observed with Palomar/WIRC and Keck/NIRSPEC. We report a band-integrated excess absorption of 0.395% ± 0.072% with Palomar/WIRC and a spectroscopically resolved 5.5 ± 0.94 km s−1 blueshifted absorption of 2.4% ± 0.52% (T1─T4) and 3.5% ± 0.72% (T2─T3) with Keck/NIRSPEC. These measurements indicate the presence of an extended escaping atmosphere. Fitting these signals with a Parker wind model, we determine a corresponding atmospheric mass-loss rate of log( ) = 10.2─10.65 g s−1 for thermosphere temperatures between 7900 and 8600 K. This relatively low rate suggests that this planet would not have been significantly altered by mass loss even if it formed in situ. However, the presence of a white dwarf companion, TOI-1259 B, hints that this planet may not have formed close-in, but rather migrated inward relatively late. Given the estimated parameters of the proto−white dwarf companion, we find that high-eccentricity migration is possible for the system.

Keywords: Exoplanets, Planetary atmospheres, Exoplanet astronomy, Exoplanet evolution, Extrasolar gaseous planets, Extrasolar gaseous giant planets, Exoplanet atmospheres
Demise of Kreutz Sungrazing Comet C/2024 S1 (ATLAS). Most Kreutz family sungrazing comets are discovered only days before perihelion, severely limiting observational opportunities to study their physical nature and decay. Kreutz sungrazer C/2024 S1 (ATLAS) was discovered a month before reaching its perihelion distance of 0.008 au, allowing physical observations from both ground- and space-based telescopes. We present observations from 0.9 to 0.4 au using the Nordic Optical Telescope showing that (1) nucleus disintegration was ongoing already at 0.7 au pre-perihelion, (2) the activity varied unpredictably with distance, and (3) the nucleus radius was &lt;600 m (red geometric albedo 0.04 assumed). We also use coronagraphic observations from the STEREO-A spacecraft to study C/2024 S1 at heliocentric distances ≲ 0.1 au. We find that the coma scattering cross section peaked near 0.075 au and faded progressively, by a factor ∼20, toward the last observation at 0.02 au. We interpret the near-perihelion fading as a result of the sublimation of refractory coma grains, beginning at blackbody temperatures ∼1000 K, consistent with olivine composition. The comet was not detected after perihelion. We consider processes operating to destroy the nucleus when near perihelion, concluding that rotational instability and sublimation losses work together toward this end, even before entry of the comet into the Roche lobe of the Sun.

Keywords: Long period comets, Comets, Near-sun comets, Kreutz group
The Clear Sky Corridor: Insights Towards Aerosol Formation in Exoplanets Using an AI-based Survey of Exoplanet Atmospheres. Producing optimized and accurate transmission spectra of exoplanets from telescope data has traditionally been a manual and labor intensive procedure. Here we present the results of the first attempt to improve and standardize this procedure by using artificial-intelligence-based (AI-based) processing of light curves and spectroscopic data from transiting exoplanets observed with the Hubble Space Telescope's (HST) Wide Field Camera (WFC3) instrument. We implement an AI-based parameter optimizer that autonomously operates the Eureka! pipeline to produce homogeneous transmission spectra of publicly available HST WFC3 datasets, spanning exoplanet types from hot Jupiters to sub-Neptunes. Surveying 42 exoplanets with temperatures between 280 and 2580 K, we confirm modeled relationships between the amplitude of the water band at 1.4 μm of hot Jupiters and their equilibrium temperatures. We also identify a similar, novel trend in Neptune/sub-Neptune atmospheres, but shifted to cooler temperatures. Excitingly, a planet-mass versus equilibrium-temperature diagram reveals a "Clear Sky Corridor," where planets between 700 and 1700 K (depending on the mass) show stronger 1.4 μm H2O band measurements. This novel trend points to metallicity as a potentially important driver of aerosol formation. With HST sculpting this foundational understanding for aerosol formation in various exoplanet types ranging from Jupiters to sub-Neptunes, we present a compelling platform for the James Webb Space Telescope to discover similar atmospheric trends for more planets across a broader wavelength range.

Keywords: Hubble Space Telescope, Exoplanet atmospheres, Astronomy data analysis, Exoplanets
Gaia-4b and 5b: Radial Velocity Confirmation of Gaia Astrometric Orbital Solutions Reveal a Massive Planet and a Brown Dwarf Orbiting Low-mass Stars. Gaia astrometry of nearby stars is precise enough to detect the tiny displacements induced by substellar companions, but radial velocity (RV) data are needed for definitive confirmation. Here we present RV follow-up observations of 28 M and K stars with candidate astrometric substellar companions, which led to the confirmation of two systems, Gaia-4b and Gaia-5b, identification of five systems that are single lined but require additional data to confirm as substellar companions, and the refutation of 21 systems as stellar binaries. Gaia-4b is a massive planet (M = 11.8 ± 0.7 MJ) in a P = 571.3 ± 1.4 day orbit with a projected semimajor axis a0 = 0.312 ± 0.040 mas orbiting a 0.644 ± 0.02M⊙ star. Gaia-5b is a brown dwarf (M = 20.9 ± 0.5MJ) in a P = 358.62 ± 0.20 days eccentric e = 0.6423 ± 0.0026 orbit with a projected angular semimajor axis of a0 = 0.947 ± 0.038 mas around a 0.34 ± 0.03M⊙ star. Gaia-4b is one of the first exoplanets discovered via the astrometric technique, and is one of the most massive planets known to orbit a low-mass star.

Keywords: Brown dwarfs, Astrometric exoplanet detection, Exoplanets, Radial velocity, Exoplanet systems, Extrasolar gaseous planets, Astrometry, Exoplanet detection methods, Exoplanet formation
Thermal Variability in the Martian Upper Atmosphere within the Crustal Magnetic Field Region Induced by Gravity Wave Dissipation Due to Ion-drag Effect. Mars Atmosphere and Volatile Evolution detected a significant temperature increase of approximately 20–40 K in the upper atmosphere within the strong crustal magnetic field (CF) region during two deep dip campaigns. Previous studies were unable to fully explain this thermal variation. Atmospheric gravity waves are an underlying mechanism, attributed to the ion-drag effect. During this effect process, the collisions between neutral particles and ions transfer wave momentum along the magnetic field lines, and lead to wave dissipation and energy release to heat or cool the background atmosphere. We developed a one-dimensional linear wave model to describe the effect of ion-drag on wave propagation and dissipation in the Martian upper atmosphere. Our results show that the ion-drag effect influences wave propagation primarily above 160 km in the CF region and around 200 km in the noncrustal magnetic field (NCF) region. The total wave energy flux driven by the ion-drag effect in the CF region is approximately 108 eV cm‑2 s‑1, with heating rates of 10–60 K per sol and cooling rates up to 40 K per sol above 155 km. Wave-driven temperature enhancements in the CF region due to the ion-drag effect are a few Kelvins higher than in the NCF regions, though still smaller than the observed 20–40 K. Additional wave processes, including wave breaking and multiwave dissipation, may contribute to the observed thermal variability and should be considered in future studies.

Keywords: Internal waves, Mars, Planetary ionospheres, Upper atmosphere
Revised Masses for Low-density Planets Orbiting the Disordered M-dwarf System TOI-1266. We present an analysis of 126 new radial velocity measurements from the MAROON-X spectrograph to investigate the TOI-1266 system, which hosts two known transiting sub-Neptunes at 10.8 and 18.8 days. We integrated our measurements with existing HARPS-N measurements for this system and derived revised masses for TOI-1266 b and c of Mb = 4.09 ± 0.45M⊕ and Mc = 2.64 ± 0.52M⊕, respectively. The Keplerian fit from the combined datasets enabled an ≍35% and ≍41% improvement in mass precision for planet b and c, respectively, compared to the previously published values. With bulk densities of ρb = 1.25 ± 0.21 g cm−3 and ρc = 1.51 ± 0.39 g cm−3, the planets are among the lowest density sub-Neptunes orbiting an M dwarf. They are both consistent with rocky cores surrounded by hydrogen helium envelopes. TOI-1266 c may also be consistent with a water-rich composition, but we disfavor that interpretation from an Occam's razor perspective.

Keywords: Exoplanet atmospheric composition , Radial velocity, Exoplanet systems, Exoplanet astronomy, Exoplanet evolution, Exoplanet detection methods
Multiepoch Observations of the Nearby Spiral Galaxy NGC 3938 with the Chandra X-Ray Observatory. We present an analysis of two epochs of ACIS observations of the SA(s)c spiral galaxy NGC 3938 with the Chandra X-ray Observatory. The total exposure time of the observations was 95 ks, with a limiting unabsorbed luminosity of ≍1038 erg s−1 assuming a distance of 22 Mpc. A total of 47 discrete merged sources from both epochs were detected at the ≍3σ level or greater with the D25 radius. We demonstrate that at the time of the Chandra observations the nucleus was not detected. We connect the detected sources to counterparts in other wavebands to the degree possible. Based on the two epochs, we identify three variable sources and an additional two that may have varied between the two observations. We do not formally detect any of the five historical supernovae that have occurred in NGC 3938. The luminosity function of NGC 3938 is compared to a recent compilation of 38 galaxies, and we identify a potentially significant problem with the "known" distance to NGC 3938. Star formation rate and metallicity values are also computed; the star formation rate is highly dependent on the adopted distance. The metallicity appears to lie in the range of 8.2─9.2, consistent with values from other work. We include in an appendix a short discussion of the sources that lie in Chandra's field of view but lie outside of NGC 3938.

Keywords: X-ray astronomy, X-ray sources, Spiral galaxies
An HST Transmission Spectrum of the Closest M Dwarf Transiting Rocky Planet LTT 1445Ab. Which rocky exoplanets have atmospheres? This presumably simple question is the first that must be answered to understand the prevalence of nearby habitable planets. A mere 6.9 pc from Earth, LTT 1445A is the closest transiting M dwarf system, and its largest known planet, at 1.31 R⊕ and 424 K, is one of the most promising targets in which to search for an atmosphere. We use Hubble Space Telescope/Wide Field Camera 3 transmission spectroscopy with the G280 and G141 grisms to study the spectrum of LTT 1445Ab between 0.2 and 1.65 μm. In doing so, we uncover an ultraviolet (UV) flare on the neighboring star LTT 1445C that is completely invisible at optical wavelengths; we report one of the first simultaneous near-UV/optical spectra of an M dwarf flare. The planet spectrum is consistent with a flat line (with median transit depth uncertainties of 128 and 52 ppm for the G280 and G141 observations, respectively), though the infrared (IR) portion displays potential features that could be explained by known opacity sources such as HCN. Some atmospheric retrievals weakly favor (∼2σ) an atmosphere, but it remains challenging to discern between stellar contamination, an atmosphere, and a featureless spectrum at this time. We do, however, confidently rule out ≤100× solar metallicity atmospheres. Although stellar contamination retrievals cannot fit the IR features well, the overall spectrum is consistent with stellar contamination from hot or cold spots. Based on the UV/optical data, we place limits on the extent of stellar variability expected in the near-IR (30–40 ppm), which will be critical for future James Webb Space Telescope observations.

Keywords: Extrasolar rocky planets, M dwarf stars, Exoplanet atmospheric composition , Transmission spectroscopy, Exoplanet astronomy, Stellar flares, Exoplanet atmospheres
Exoplanet Occurrence Rate with Age for FGK Stars in Kepler. We measure the exoplanet occurrence rate as a function of isochrone and gyrochronology ages using confirmed and candidate planets identified in Q1–17 DR25 Kepler data. We employ Kepler's pipeline detection efficiency to correct for the expected number of planets in each age bin. We examine the occurrence rates for planets with radii 0.2 ≤ Rp ≤ 20 R⊕ and orbital periods 0.2 ≤ P ≤ 100 days for FGK stars with ages between 1.5 and 8 Gyr using the inverse detection-efficiency method. We find no significant trend between the occurrence rate and stellar age; a slight decreasing trend (within 1.5σ–2.5σ) only emerges for the low-mass and metal-rich stars that dominate our sample. We isolate the effects of mass and metallicity on the occurrence rate trend with age, but find the results to be inconclusive, due to weak trends and the small sample size. Our results hint that the exoplanet occurrence rate may decrease over time due to dynamical instability from planet–planet scattering or planet ejection, but accurate ages and larger sample sizes are needed to resolve a clear relation between the occurrence rate and age.

Keywords: Exoplanet astronomy, Exoplanet evolution, Exoplanet dynamics
Distributions of Wide Binary Stars in Theory and in Gaia Data. I. Generalized Ambartsumian (1937) Approach and the Family of Power-law Distributions of Eccentricity. The orbital parameter space of wide, weakly bound binary stars has been shaped by the still poorly known circumstances of their formation, as well as by subsequent dynamical evolution in parent clusters and in the field. The advance of the Gaia mission astrometry takes statistical studies of wide stellar systems to an unprecedented level of precision and scope. On the theoretical side of the problem, the old approach proposed by Jeans and developed by Ambartsumian is revisited here. It is shown how certain simplifying assumptions about the phase density of binary systems in the framework of general copula distributions can lead to a family of analytical representations for the marginal distribution of orbital eccentricity, including accommodating and flexible power-law models. We further demonstrate the application of these models in forward Monte Carlo simulations of the measured motion angles between the relative velocity and separation vectors on the example of 170 K listed Gaia binary systems, providing inference in the intrinsic distribution of orbital eccentricity.

Keywords: Orbital elements, Monte Carlo methods, Orbital evolution, Astrostatistics distributions, Wide binary stars, Gaia
WALLABY Pilot Survey and ASymba: Comparing H I Detection Asymmetries to the SIMBA Simulation. An avenue for understanding cosmological galaxy formation is to compare morphometric parameters in observations and simulations of galaxy assembly. In this second paper of the ASymba: Asymmetries of H I in SIMBA Galaxies series, we measure atomic gas (H I) asymmetries in spatially resolved detections from the untargeted Widefield ASKAP L-band Legacy All-sky Blind surveY (WALLABY) survey, and compare them to realizations of WALLABY-like mock samples from the SIMBA cosmological simulations. We develop a Scanline Tracing method to create mock galaxy H I data cubes that minimizes shot noise along the spectral dimension, compared to particle-based methods, and thus minimizes spurious asymmetry contributions. We compute 1D and 3D asymmetries for spatially resolved WALLABY Pilot Survey detections, and we find that the highest 3D asymmetries (A3D ≳ 0.5) stem from interacting systems or detections with strong bridges or tails. We then construct a series of WALLABY-like mock realizations drawn from the SIMBA 50 Mpc simulation volume and compare their asymmetry distributions. We find that the incidence of high A3D detections is higher in WALLABY than in the SIMBA mocks, but that difference is not statistically significant (p-value = 0.05). The statistical power of quantitative comparisons of asymmetries such as the one presented here will improve as the WALLABY survey progresses and as simulation volumes and resolutions increase.

Keywords: Hydrodynamical simulations, Galaxy structure, H I line emission
Forest Fire Clustering: A Novel Tool for Identifying Star Members of Clusters. In the era of a data-driven landscape, the development of an efficient and interpretable method has become a pivotal tool for robustly identifying memberships of clusters. We present a novel cluster finder approach called forest fire clustering (FFC). FFC combines iterative label propagation with parallel Monte Carlo simulation to achieve internal validation of clustering results. We use a Gaia DR3 catalog comprising 322 random objects with distinct heliocentric distances from approximately 0 to 5 kpc, along with one ultrafaint dwarf galaxy Bootes I (∼63 kpc), as our validation sample. We compare the performance of FFC with that of DBSCAN and HDBSCAN on this data set by configuring them into the same processing pipeline for identifying star members. Our results indicate that FFC outperforms the two others in terms of the quality of clusters, particularly for clusters located at distances greater than 2 kpc. Additionally, FFC demonstrates robust performance and efficiency. Based on the high-quality clusters derived from FFC, we provide a detailed analysis of cluster properties. We determine various cluster parameters, including age, mass, [Fe/H], distance modulus, reddening, and binary fraction. Furthermore, dynamic properties are reliably estimated through the fitting of radial density profiles and theoretical models. This study suggests that FFC is a suitable tool for identifying reliable memberships of stellar systems, highlighting the discovery of more distant clusters and enabling the identification of high-quality clusters to accurately uncover cluster properties.

Keywords: Open star clusters, Astronomy data analysis, Star clusters
Photometric Determination of Unresolved Main-sequence Binaries in the Pleiades: Binary Fraction and Mass-ratio Distribution. Accurate determination of binary fractions (fb) and mass ratio (q) distributions is crucial for understanding the dynamical evolution of open clusters. We present an improved multiband fitting technique to enhance the analysis of binary properties. This approach enables an accurate photometric determination of fb and q distribution in a cluster. The detectable mass ratio can be down to the  , limited by the minimum stellar mass in theoretical models. First, we derived an empirical model for magnitudes of Gaia DR3 and 2MASS bands that match the photometry of single stars in the Pleiades. We then performed a multiband fitting for each cluster member, deriving the probability density function (PDF) of its primary mass ( ) and q in the Bayesian framework. 1154 main-sequence (MS) single stars or unresolved MS+MS binaries are identified as members of the Pleiades. By stacking their PDFs, we conducted a detailed analysis of binary properties of the cluster. We found the fb of this sample is 0.34 ± 0.02. The q distribution exhibits a three-segment power-law profile: an initial increase, followed by a decrease, and then another increase. This distribution can be interpreted as a fiducial power-law profile with an exponent of −1.0 that is determined in the range of 0.3 &lt; q &lt; 0.8, but with a deficiency of binaries at lower q and an excess at higher q. The variations of fb and q with   reveal a complex binary distribution within the Pleiades, which might be attributed to a combination of primordial binary formation mechanisms, dynamical interactions, and the observational limit of photometric binaries imposed by  .

Keywords: Open star clusters, Bayesian statistics, Binary stars, Mass ratio
The Hottest Neptunes Orbit Metal-rich Stars. The Neptune desert is no longer empty. A handful of close-in planets with masses between those of Neptune and Saturn have now been discovered, and their puzzling properties have inspired a number of interesting theories on the formation and evolution of desert-dwellers. While some studies suggest that Neptune desert planets form and evolve similarly to longer-period Neptunes, others argue that they are products of rare collisions between smaller planets, or that they are the exposed interiors of giant planets (i.e., "hot Jupiters gone wrong"). These origin stories make different predictions for the metallicities of Neptune desert host stars. In this paper, we use the homogeneous catalog of stellar metallicities from Gaia Data Release 3 to investigate the origins of Neptune desert dwellers. We find that planets in the Neptune desert orbit stars that are significantly more metal rich than the hosts of longer-period Neptunes (p = 0.0016) and smaller planets (p = 0.00014). In contrast, Neptune desert host star metallicities are statistically indistinguishable from those of hot Jupiter host stars (p = 0.55). Therefore, we find it relatively unlikely that Neptune desert planets formed and evolved similarly to longer-period Neptunes, or that they resulted from collisions between smaller planets, at least without another metallicity-selective process involved. A more straightforward explanation for this result is that planets in the desert truly are the exposed interiors of larger planets. Atmospheric spectroscopy of Neptune desert worlds may therefore provide a rare glimpse into the interiors of giant exoplanets.

Keywords: Hot Neptunes, Metallicity, Exoplanets
Earth Detecting Earth: At What Distance Could Earth's Constellation of Technosignatures Be Detected with Present-day Technology?. The field of Search for Extraterrestrial Intelligence (SETI) searches for "technosignatures" could provide the first detection of life beyond Earth through the technology that an extraterrestrial intelligence may have created. Any given SETI survey, if no technosignatures are detected, should set upper limits based on the kinds of technosignatures it should have been able to detect; the sensitivity of many SETI searches requires that their target sources (e.g., Dyson spheres or Kardashev II/III level radio transmitters) emit with power far exceeding the kinds of technology humans have developed. In this paper, we instead turn our gaze Earthward, minimizing the axis of extrapolation by only considering transmission and detection methods commensurate with an Earth 2024 level. We evaluate the maximum distance of detectability for various present-day Earth technosignatures—radio transmissions, atmospheric technosignatures, optical and infrared signatures, and objects in space or on planetary surfaces—using only present-day Earth instruments, providing one of the first fully cross-wavelength comparisons of the growing toolbox of SETI techniques. In this framework, we find that Earth's space-detectable signatures span 13 orders of magnitude in detectability, with intermittent, celestially targeted radio transmission (i.e., planetary radar) beating out its nearest nonradio competitor by a factor of 103 in detection distance. This work highlights the growing range of ways that exoplanet technosignatures may be expressed, the growing complexity and visibility of the human impact upon our planet, and the continued importance of the radio frequencies in SETI.

Keywords: Search for extraterrestrial intelligence, Technosignatures, Earth (planet)