Sazuna/UAT_keywords huggingface dataset:
Keck Observations in the INfrared of Taurus and ρ Oph Exoplanets And Ultracool Dwarfs (KOINTREAU). II. Two Young Bound Companions to Ophiuchus Stars. We present the second set of discoveries from Keck Observations in the INfrared of Taurus and ρ Oph Exoplanets And Ultracool dwarfs (KOINTREAU), an adaptive optics survey of young stars in the Taurus and ρ Oph star-forming regions using Keck/NIRC2 in conjunction with the Keck infrared pyramid wavefront sensor. We have discovered two faint comoving companions to young stars ISO-Oph 96 and 2MASS J16262785−2625152. The companion to ISO-Oph 96, KOINTREAU-3b, is at a projected separation of 340 au (2 .″ 49). Using our NIRC2 photometry and evolutionary models, and assuming that the companion has the same extinction as its host star, we infer that KOINTREAU-3b has a mass of 3.4 ± 0.7 MJup. The companion to 2MASS J16262785−2625152, KOINTREAU-4b, has a projected separation of 180 au (1 .″ 25) and could have a mass of either  11.5−1.6+1.2  MJup or  15.3−0.8+0.7  MJup, depending on whether the host star is a member of ρ Oph or Upper Sco.

Keywords: Direct imaging, Exoplanets
A Multimethod Age Determination for the Ursa Major Moving Group. The Ursa Major Moving Group (UMa) is one of the closest stellar associations, yet its age has remained controversial, with published estimates ranging from 200 Myr to 1 Gyr. We present a comprehensive age analysis using the largest sample of candidate UMa members to date. Using Gaia DR3, we identify 1172 stars within 100 pc of the Sun with 3D kinematic motions consistent with group membership. We determine the age of UMa's dominant population using three independent methods: lithium equivalent widths ( 393.6−80.9+85.1  Myr), gyrochronology (428 ± 93 Myr), and photometric variability indicators ( 449−79+114  Myr). The three methods converge on a consistent age of  418−34+32  Myr. While our kinematic selection includes field stars that share UMa's space motion but are not coeval members, the convergent age determinations clearly identify a dominant population that formed together 400 Myr ago. These stars are important benchmarks for studies of stellar rotation, magnetic activity evolution, and lithium depletion. The presence of systems such as HD 63433, a young multiplanet host within the group, further illustrates the value of UMa as a laboratory for early planetary system evolution. Our expanded catalog of kinematic candidates lays the groundwork for spectroscopic membership confirmation, refined mapping of the group's structure and chemistry, and future investigations of both stellar and planetary evolution at this key epoch.

Keywords: Moving clusters, Stellar ages, Young star clusters, Planet hosting stars, Stellar rotation
Follow-up Observations of Candidate White Dwarf Planets with MIRI. We report on second-epoch imaging of two candidate planet-hosting white dwarf (WD) stars, WD 2105−82 and WD 1202−232. Both stars showed evidence of resolved, planet-mass candidate companions in observations using the MIRI mid-infrared imager on JWST. WD 2105 also showed evidence of an infrared excess consistent with an unresolved 1.4 MJ companion with an orbital separation of &lt;4 au. Our second epoch observations confirm that the source of the excess shares common proper motion with the star. The excess is almost certainly due to a companion planet or debris disk. However, neither of the two resolved sources with projected separations of &gt;1″ in the first epoch of JWST observations show measurable proper motion and are thus likely faint, unresolved background galaxies. We also search for common proper-motion companions out to hundreds of astronomical unit, but find no evidence of widely separated companions.

Keywords: Accretion, Astrometric exoplanet detection, White dwarf stars, Exoplanet astronomy, Direct imaging, DA stars, Stellar accretion
Unveiling Fiber Networks and Core Formation in the DR21 South Filament. We present high-resolution (∼1000 au) 3 mm observations with the NOrthern Extended Millimeter Array toward the DR21 South Filament (DR21SF), aiming to reveal its internal fragmentation and search for deeply embedded star-forming activities. Both the continuum and molecular line emissions align well with the filament axis traced by the low-resolution (∼18″) column density map. The 3 mm continuum, CS (2─1), and HCO+ (1−0) emissions reveal continuous and diffuse structures with measured full width half maximum widths of 0.054, 0.029, and 0.030 pc, respectively. In contrast, the H13CO+ (1−0) emission appears more clumpy and localized. The non-thermal motion in the filament is predominantly subsonic to transonic. We detect 13 dense cores in NH2D (111−101), three of which coincide with continuum peaks; virial analysis suggests most are gravitationally bound. Using a friend-of-friend algorithm, we identify 32, 34, and 22 velocity-coherent fibers from the CS, HCO+, and H13CO+ data, respectively. Compared to fibers traced by CS and HCO+, H13CO+ fibers are more frequently associated with NH2D cold cores and exhibit higher average mass-per-unit-length values. Differences among CS, HCO+, and H13CO+ emissions likely arise from variations in effective critical densities. These results are consistent with a hierarchical structure, in which the 3.6 pc DR21SF contains velocity-coherent fibers and gravitationally bound dense cores.

Keywords: Interstellar line emission, Interstellar filaments, Star forming regions, Star formation, Dust continuum emission
Searching for GEMS: The Occurrence of Giant Planets Orbiting M Dwarfs within 100 pc. We present results from a systematic search for transiting short-period giant exoplanets around M dwarf stars (GEMS; P &lt; 10 days, Rp ≳ 8R⊕) within a distance-limited 100 pc sample of 149,316 M dwarfs using TESS-Gaia Light Curve (or TGLC) data. We describe the development and application of the TESS-miner package and associated vetting procedures used in this analysis. To assess detection completeness, we conducted ∼72 million injection-recovery tests across ∼26,000 stars with an average of ∼3 sectors of data per star, subdivided into early-type (M0─M2.5), mid-type (M2.5─M4), and late-type (M4 or later) M dwarfs. Our pipeline demonstrates high sensitivity across all subtypes within the injection bounds. We estimate the occurrence rates of short-period GEMS as a function of stellar mass, and combine our measured rates with those derived for FGK stars, fitting an exponential trend with stellar mass, consistent with core-accretion theory predictions. We find GEMS occurrence rates of 0.118% ± 0.068% for early-type M dwarfs, 0.153% ± 0.069% for mid-type M dwarfs, and 0.036% ± 0.024% for late-type M dwarfs, with a mean rate of 0.068% ± 0.024% across the full sample. While our search spanned 1.0 day &lt; P &lt; 10.0 days, these rates were calculated using planets orbiting with 1.0 day &lt; P &lt; 5.0 days. This work establishes the basis for future occurrence-rate studies of transiting GEMS.

Keywords: M dwarf stars, Transits, Extrasolar gaseous giant planets
A Comprehensive Analysis of the Panchromatic Transmission Spectrum of the Hot-Saturn WASP-96 b: Nondetection of Haze, Possible Sodium Limb Asymmetry, Stellar Characterization, and Formation History. We conduct a reanalysis of the JWST NIRISS/SOSS observation of the hot-Saturn WASP-96 b. Initial analysis of this data revealed an enhanced Rayleigh scattering slope at the blue end of the transmission spectrum, suggesting the presence of hazes at high altitudes. In this work, we report nondetection of this slope, confirming an atmosphere clear of high-altitude aerosols consistent with the pre-JWST results. Also contrary to the initial result, our results indicate the presence of gray cloud deck, although at relatively low altitudes/high pressures. We further combined the NIRISS/SOSS spectrum with the Very Large Telescope, Hubble Space Telescope, and Spitzer to produce a transmission spectrum from 0.35─5 μm. We constrain the mass fraction of multiple chemical species, including: H2O  =−2.62−0.42+0.43 , K  =−5.76−1.13+1.05 , and Na  =−3.40−0.92+0.90 . C/O ratio and metallicity are tentatively constrained at substellar values ( C/Oplanet=0.57−0.12+0.07  and  [Fe/H]planet=0.01−0.52+0.46  compared to C/Ostar = 0.92 ± 0.25 and [Fe/H]star = 0.24 ± 0.05). Inputting these composition constraints to interior structure models, we constrain a core mass of  43−15+8  M⊕. This, in addition to our inferred super-stellar refractory-to-oxygen ratio ( ∆log10(R/O)=1.48−0.62+0.57 ) and substellar C/O ratio, suggests that the core of WASP-96 b likely formed outside of the water ice line, underwent disk-driven migration, and accreted its atmosphere inside the carbon soot line. We find evidence of atmospheric leading-trailing terminator asymmetries in the broadened sodium absorption feature with a transit time offset of 50 s, while the water features appear symmetric. CH4, CO, and CO2 remain unconstrained due to spectral coverage limits. Upcoming JWST NIRSpec/G395H observations (ID 4082, PI: M. Radica) will be crucial for constraining these carbon-bearing species.

Keywords: Exoplanet atmospheric composition , Bayesian statistics, Stellar ages, Exoplanets, Stellar abundances, Planet formation, Transmission spectroscopy, Astrochemistry, James Webb Space Telescope, Protoplanetary disks, Planetary interior, Exoplanet atmospheres
Architectures of Planetary Systems. II. Trends with Host Star Mass and Metallicity. The current census of planetary systems displays a wide range of architectures. Extending earlier work, this paper investigates the correlation between our classification framework for these architectures and host stellar properties. Specifically, we explore how planetary system properties depend on stellar mass and stellar metallicity. This work confirms previously detected trends that Jovian planets are less prevalent for low-mass and low-metallicity stars. We also find new, but expected trends such as that the total mass in planets increases with stellar mass, and that observed planetary system masses show an upper limit that is roughly consistent with expectations from the stability of circumstellar disks. We tentatively identify potential, unique trends in the host stars of superpuffs and hot Jupiters and a possible subdivision of the class of hot Jupiter systems. In general, we find that system architectures are not overly dependent on host star properties.

Keywords: Exoplanet dynamics, Exoplanet catalogs, Exoplanet systems, Exoplanet astronomy, Planet hosting stars
Unreported ICCD Speckle Interferometry Measures of Double Stars. We report here on 1057 speckle interferometric double star measures obtained between 1997 and 2018 by the Center for High Angular Resolution Astronomy group at Georgia State University and the Double Star Group at the U.S. Naval Observatory. These measures "fell through the cracks" for various reasons, including personnel changes, equipment failures and upgrades, incomplete or abandoned survey projects, and delays in verification of uncertain measures, so they have never been previously published. We also present six new orbital solutions based in part on these measures.

Keywords: White dwarf stars, Binary stars, Speckle interferometry
A JWST Transit of a Jupiter Analog. I. Constraints on the Oblateness of Kepler-167 e. In 2024 October, JWST observed a transit of Kepler-167 e, a Jupiter-analog planet on a 1000+ day orbit. These observations, recorded over a long baseline of nearly 60 hr, were designed to search for signatures of planetary oblateness and/or exomoons comparable to Ganymede. In this first in a series of studies analyzing these data, we report on constraints on Kepler-167 e's oblateness. We explored a large grid of data reduction pipelines and modeling choices, including a new entirely independent reduction pipeline ("katahdin") and two new treatments for limb darkening. We find that under a Bayesian model comparison framework the data are fit equally well by both spherical and oblate planet models, and that our ability to constrain the oblateness is negatively impacted by the influence of exposure-long trends. Using the most conservative of our posteriors, we place a 95% upper bound on the projected oblateness of f &lt; 0.097, which corresponds to a rotation period of P ≥ 7.11 hr if the planet's spin axis is aligned with the sky plane. We note, however, that the final bound depends on the choice of reduction pipeline and systematics model, and that our suite of end-to-end analyses produced bounds as low as f &lt; 0.065 at 95%. We conclude that leveraging JWST to make tighter constraints on planetary oblateness will require further investigation into mitigating exposure-long trends and correlated noise.

Keywords: Transit photometry, Extrasolar gaseous planets, Oblateness
KMT-2025-BLG-1616Lb: First Microlensing Bound Planet From DREAMS. We present observations and analysis of the bound planetary microlensing event KMT-2025-BLG-1616. The planetary signal was captured by the Korea Microlensing Telescope Network and the Dark Energy Camera Rogue Earths and Mars Survey (DREAMS). DREAMS's minute-cadence observations break the central/resonant degeneracy in the binary-lens models. The color of the faint source star (I = 22) is measured from the DREAMS's r − z color. The planetary system has a planet-host mass ratio of q ∼ 5 × 10−4. A Bayesian analysis yields a host-star mass of ∼0.3 M⊙, a planetary mass of ∼40 M⊕, a projected planet-host separation of ∼1.6 au, and a lens distance of ∼7.5 kpc. Based on the photometric precision achieved by DREAMS for this event, we simulate free-floating planet (FFP) detections and find that DREAMS is sensitive to Mars-mass FFPs in the Galactic bulge and Moon-mass FFPs in the Galactic disk.

Keywords: Gravitational microlensing, Exoplanet detection methods, Gravitational microlensing exoplanet detection, Free floating planets
The Column Density Probability Density Function of Cygnus-X. The density distribution within molecular clouds offers critical insights into their underlying physical processes, which are essential for understanding star formation. As a statistical measure of column density on the cloud scale, the shape and evolution of the column density probability density function (N-PDF) serve as important tools for understanding the dynamics between turbulence and gravity. Here, we investigate the N-PDFs of Cygnus-X using the column density map obtained from Herschel, supplemented by H I and young stellar objects data. We find that the N-PDFs of Cygnus-X and four subregions display log-normal + power-law shapes, indicating the combined effects of turbulence and gravity in sculpting the density structure. We find evidence that the power-law segment of the N-PDFs flattens over time, and the transitional column density can be seen as a unique and stable star formation threshold specific to each molecular cloud. These results not only clarify the physical state of Cygnus-X but also emphasize the utility of the N-PDF as a statistical diagnostic tool, as it is an accessible indicator of evolutionary stages and star formation thresholds in molecular clouds.

Keywords: Giant molecular clouds, Star formation, Interstellar medium, Astrostatistics
Tidal Stripping as the Driver of Mass Segregation in the Young Open Cluster NGC 2422. We present strong evidence that mass segregation in the young open cluster NGC 2422 (age ≍84 Myr) is primarily driven by tidal stripping. Analysis of the radial mass distribution reveals a significant overabundance of low-mass stars (M &lt; 0.85 M⊙) preferentially located near and beyond the cluster's tidal radius (rt = 14.4 pc), a hallmark of ongoing tidal stripping. This spatial signature is corroborated by kinematic evidence: the cluster's outskirts exhibit an elevated velocity dispersion (σ3d = 14.9 km s−1, F-test p &lt; 0.001) and strong radial anisotropy (β = 0.94 ±0.4), both classic signatures of tidal influence. The cluster's age is significantly greater than its half-mass relaxation time (trh = 44.2 Myr), confirming it is dynamically evolved. Crucially, binary stars show no significant radial segregation from single stars (KS-test p ≍ 0.51), ruling them out as the primary driver. Collectively, these results establish tidal stripping as the dominant mechanism currently reshaping the structure and stellar content of NGC 2422.

Keywords: Open star clusters
Undetected Past Contacts with Technological Species: Implications for Technosignature Science. In the search for extraterrestrial intelligence (SETI), the highly incomplete sampling of the technosignature search space is often considered as a plausible explanation for the persistent lack of detections over six decades of searches. If correct, this would imply that technosignatures may already have reached Earth without being detected or correctly identified. Here, we explore this possibility using a Bayesian inference framework to estimate present-day detectability given n ≥ 1 undetected contacts over the past 65 yr—the period since the first SETI experiment. We show that achieving high detectability of technosignatures emitted within a few hundred light-years of Earth would require implausibly large n values, even exceeding the population of habitable planets within that range. More conservative estimates can be obtained only assuming that emitters are tightly clustered near Earth or that their population in the Milky Way has undergone a very recent and sudden boost. This tension is further exacerbated for short-lived technosignatures and persists whether they are omnidirectional, as in Dysonian megastructures, or directional, as in intentional communication attempts. These findings suggest that, if undetected past contacts from the Milky Way have indeed occurred, the best prospects of detection may lie in searches extending over several thousand light years, though only a few detectable technoemissions would be expected.

Keywords: Search for extraterrestrial intelligence, Technosignatures, Astrobiology
Probing Thermal Gradient of Habitable-zone Rocky Planets as an Anti-indicator of a Global Surface Ocean Using Mid-infrared Direct Imaging. Future direct-imaging missions, such as the Large Interferometer for Exoplanets (LIFE), aim to observe thermal emission from potentially habitable planets to characterize their surface environments and search for signs of life. Previous studies of directly imaged Earth-like planets have mainly examined the signatures of atmospheric composition, often using 1D models, while the effect of horizontal temperature gradients has received limited attention. Because a pronounced horizontal temperature gradient may signal the absence of a global ocean, we investigate its detectability through thermal-emission direct imaging. Adopting Teegarden's Star b (zero-albedo equilibrium temperature ∼280 K) as a benchmark, we compute 3D atmospheric structures with and without a global ocean using the ROCKE-3D general circulation model and simulate geometry-dependent thermal-emission spectra. We show that the temperature gradients that disfavor a global-ocean scenario manifest in both orbital phase variation and spectral shape of the snapshot spectra. The phase variation is more readily detectable: one-day integrations with LIFE at two orbital phases would reveal flux variations in no-ocean cases with 1─10 bar atmospheres, depending on background atmospheric composition. Shapshot spectra provide complementary diagnostics of global temperature contrast, the running brightness temperature of the continuum, and detailed absorption band shapes, but require longer integration times. These 3D effects, if neglected, can bias interpretations based on 1D models. We also assess their detectability for other nearby exoplanets. Our results highlight the need to incorporate 3D atmospheric structures when characterizing rocky exoplanets, both to constrain surface conditions and to avoid misinterpretation of spectral data.

Keywords: Extrasolar rocky planets, Exoplanet atmospheric dynamics, Exoplanet surface characteristics, Habitable planets, Exoplanet atmospheres
Optimizing Structural Parameters and Layout of Fiber Positioners with the Whale Optimization Algorithm for LAMOST. Robotic fiber positioner (RFP) arrays are essential for multiobject spectroscopic telescopes. To improve the survey efficiency, they are densely arranged on the focal planes with overlapped patrol areas, guaranteeing full coverage and increasing the number of RFPs. However, this does not guarantee a proportional increase in observable targets due to collisions. To achieve optimal performance of RFPs across various target distributions, an effective method is necessary for optimizing the parameter settings and array layouts. This study addresses this challenge by applying optimization algorithms to minimize collision risks while maximizing target coverage in different configurations. Initially, the whale optimization algorithm is used to optimize RFPs with mixed arm-length ratios (three distinct ratios). The design is then refined by jointly optimizing arm length, mixed arm ratios, and variable pitch. Simulations based on the Large Sky Area Multi-Object Fiber Spectroscopic Telescope system show that RFPs with equal arm lengths and a fixed pitch of 10.4 mm provide optimal performance for both uniform and positional targets. This method offers a practical solution for designing and arranging RFPs on focal planes, thereby enhancing the performance of fiber positioning systems. Additionally, it can be applied to other major astronomical instruments such as the Dark Energy Spectroscopic Instrument and the Multi-Object Optical and Near-infrared Spectrograph.

Keywords: Astronomical techniques, Astronomical instrumentation, Wide-field telescopes
Most Hot Jupiters Were Cool Giant Planets for More Than 1 Gyr. The origin of hot Jupiters is the oldest problem in exoplanet astrophysics. Hot Jupiters formed in situ or via disk migration should be in place just a few million years after the formation of their host stars. On the other hand, hot Jupiters formed via eccentricity excitation and tidal damping as a result of planet─planet scattering or Kozai─Lidov oscillations may take 1 Gyr or more to arrive at their observed locations. We propose that the relative ages of hot Jupiters inside, near, and outside the bias-corrected peak of the observed hot Jupiter period distribution can be used to distinguish between these possibilities. Though the lack of precise and accurate age inferences for isolated hot Jupiter host stars makes this test difficult to implement, comparisons between the Galactic velocity dispersions of the hot Jupiter subpopulations enable this investigation. To transform relative age offsets into absolute age offsets, we calibrate the monotonically increasing solar neighborhood age─velocity dispersion relation using an all-sky sample of subgiants with precise ages and a metallicity distribution matched to that of hot Jupiter hosts. We find that the inside-peak and near-peak subpopulations are older than the outside-peak subpopulation, with the inside-peak subpopulation slightly older than the near-peak subpopulation. We conclude that at least 40% but not more than 70% of the hot Jupiter population must have formed via a late-time, peak-populating process like high-eccentricity migration that typically occurs more than 1.5 Gyr after system formation.

Keywords: Exoplanet dynamics, Exoplanet migration, Exoplanets, Stellar kinematics, Exoplanet evolution, Exoplanet formation