Sazuna/UAT_keywords huggingface dataset:
Centimeter-sized Grains in the Compact Dust Ring around Very-low-mass Star CIDA 1. We examined the grain size in the dust ring encircling the 0.19 M ☉ T Tauri star CIDA 1 using the Karl G. Jansky Very Large Array at multiple centimeter wavelengths, with a spatial resolution of 0.″2-0.″9. We detected distinct partial-ring structures at these wavelengths around CIDA 1. Based on spatial distributions and spectral indices, we determined that these centimeter emissions originated from dust, rather than free-free or synchrotron emissions. To estimate the maximum grain size ( ${a}_{\max }$ ) within the ring, we compared the observed spectral energy distribution (SED) with SEDs calculated for different ${a}_{\max }$ values using radiative transfer calculations. Our findings indicate an ${a}_{\max }$ value of approximately 2.5 cm in the ring, assuming that the dust opacity can be approximated by the DSHARP models. These results suggest that grain growth took place within the CIDA 1 ring, potentially facilitating more efficient planet formation through pebble accretion scenarios involving centimeter-sized pebbles.

Keywords: Protoplanetary disks
Surrounded by Giants: Habitable Zone Stability Within the HD 141399 System. The search for exoplanets has revealed a diversity of planetary system architectures, the vast majority of which diverge significantly from the template of the solar system. In particular, giant planets beyond the snow line are relatively rare, especially for low-mass stars, placing the solar system within a small category of systems with multiple giant planets at large separations. An exoplanetary system of note is that of HD 141399, consisting of a K-dwarf host star that harbors four giant planets with separations extending to ~4.5 au. The architecture of the system creates a complex pattern of mean motion resonances and gravitationally perturbed regions that may exclude the presence of other planets, including within the habitable zone of the system. Here, we present the results of dynamical simulations that explore the interaction of the known planets of the system, their apsidal trajectories, resonance locations, and dynamical evolution. We further investigate the results of injecting Earth-mass planets and provide the regions of dynamical viability within the habitable zone where terrestrial planets may maintain long-term stability. We discuss these results in the context of the importance of giant planets for volatile delivery and planetary habitability considerations.

Keywords: Exoplanet dynamics, Exoplanets, Exoplanet systems, Orbital evolution, Orbital resonances, Exoplanet astronomy, Exoplanet evolution, Astrobiology, Habitable zone, Habitable planets
V1507 CYGNI (HD187399): A Highly Evolved, Enigmatic Interacting Binary System with an Eccentric Orbit. The properties of the interacting, eccentric orbit binary V1507 Cyg (HD187399) are examined with spectra that cover wavelengths from 0.63-0.68 μm. The spectrum of the brightest star is similar to that of the B8 I star β Ori, although with absorption lines that show substructure possibly related to a varying tidal field. The bulk of the Hα emission in the spectrum appears to be associated with this star. Evidence is presented that the period of the system has been stable over timescales of many decades, arguing against large-scale mass transfer at the current epoch. Absorption and emission lines are identified that originate in an expanding asymmetric envelope around the companion, and component masses of 6.4 ± 0.9 and 14.0 ± 0.9 M ☉ are found, where the former applies to the brighter star and an inclination of 46° has been assumed. Mass transfer has thus progressed to the point where the mass ratio has reversed. It is argued that the brighter star is an α Cyg variable, and that it is those light variations that dominate the system light curve. V1507 Cyg is observed at or near the center of a diffuse H I bubble that is detected at 408 and 1420 MHz. It is suggested that the eccentric orbit is the result of evolution in a hierarchical system, in which a now-defunct massive third body recently disturbed the orbit of the stars in V1507 Cyg, thereby disrupting mass transfer.

Keywords: Close binary stars, Binary stars, Interacting binary stars
Machine-learning Morphological Classification of TESS Light Curves of T Tauri Stars. We present a variability and morphological classification study of TESS light curves for T Tauri star candidates in the Orion, IC 348, γ Velorum, Upper Scorpius, Corona Australis, and Perseus OB2 regions. We propose 11 morphological classes linking brightness variation behaviors with possible physical or geometric phenomena present in T Tauri stars, and develop a supervised machine-learning algorithm to automate the classification among these. Our algorithm optimizes and compares the true positive rate (recall) among k-nearest neighbors, classification trees, random forests, and support vector machines. This is done characterizing light curves with features depending on time, periodicity, and magnitude distribution. Binary and multiclass classifiers are trained and interpreted in a way that allows our final algorithm to have single or mixed classes. In the testing sample, the algorithm assigns mixed classes to 27% of the stars, reaching up to five simultaneous classes. A catalog of 3672 T Tauri star candidates is presented, along with their possible period estimations, predicted morphological classes, and visually revised ones. The cross-validation estimated performance of the final classifiers is reported. Binary classifiers surpass multiclass recall values for classes with less representation in the training sample. Support vector machines and random forest classifiers obtain better recalls. For comparison, another performance estimation of the final classifiers is calculated using the revised classes of our testing sample, indicating that this performance excels in singled classed stars, which happens in about 75% of the testing sample.

Keywords: Light curve classification , Astrostatistics techniques, Young stellar objects, Protoplanetary disks, Variable stars
The Most Sensitive SETI Observations Toward Barnard's Star with FAST. Search for extraterrestrial intelligence (SETI) has been mainly focused on nearby stars and their planets in recent years. Barnard's star is the second closest star system to the Sun and the closest star in the Five-hundred-meter Aperture Spherical radio Telescope (FAST) observable sky which makes the minimum Equivalent Isotropic Radiated Power required for a hypothetical radio transmitter from Barnard's star to be detected by FAST telescope a mere 4.36 × 108 W. In this paper, we present the FAST telescope as the most sensitive instrument for radio SETI observations toward nearby star systems and conduct a series of observations to Barnard's star (GJ 699). By applying the multibeam coincidence matching strategy on the FAST telescope, we search for narrow-band signals (~Hz) in the frequency range of 1.05-1.45 GHz, and two orthogonal linear polarization directions are recorded. Despite finding no evidence of radio technosignatures in our series of observations, we have developed predictions regarding the hypothetical extraterrestrial intelligence signal originating from Barnard's star. These predictions are based on the star's physical properties and our observation strategy.

Keywords: Search for extraterrestrial intelligence, Technosignatures, Astrobiology, Exoplanets
Physical Properties of the Young Asteroid Pair 2010 UM26 and 2010 RN221. The main belt asteroids 458271 (2010 UM26) and 2010 RN221 share almost identical orbital elements, and currently appear as comoving objects ~30″ apart in the plane of the sky. They are products of the breakup of a parent object, or the splitting of a binary, with a separation age measured in decades rather than thousands or millions of years as for most other asteroid pairs. The nature of the precursor body and the details of the breakup and separation of the components are unknown. We obtained deep, high-resolution imaging using the Hubble Space Telescope to characterize the pair and to search for material in addition to the main components that might have been released upon breakup. The primary and secondary have absolute magnitudes H = 17.98 and 19.69, respectively, and effective diameters 760 and 350 m (assuming geometric albedo 0.20). The secondary/primary mass ratio is 0.1, assuming equal densities. Time-series photometry shows that the primary rotates with period ~5.9 hr and has a small photometric range (0.15 mag), while the period of the secondary is undetermined (but ≳20 hr) and its lightcurve range is at least 1 mag. The primary rotation period and component mass ratio are consistent with a simple model for the breakup of a rotationally unstable precursor. However, unlike other observationally supported instances of asteroid breakup, neither macroscopic fragments nor unresolved material are found remaining in the vicinity of this asteroid pair. We suggest that the pair is a recently dissociated binary, itself formed earlier by rotational instability of 2010 UM26.

Keywords: Asteroid satellites, Asteroid rotation, Asteroids
Atmospheric Retrieval of L Dwarfs: Benchmarking Results and Characterizing the Young Planetary Mass Companion HD 106906 b in the Near-infrared. We present model constraints on the atmospheric structure of HD 106906 b, a planetary-mass companion orbiting at a ~700 au projected separation around a 15 Myr old stellar binary, using the APOLLO retrieval code on spectral data spanning 1.1-2.5 μm. C/O ratios can provide evidence for companion formation pathways, as such pathways are ambiguous both at wide separations and at star-to-companion mass ratios in the overlap between the distributions of planets and brown dwarfs. We benchmark our code against an existing retrieval of the field L dwarf 2MASSW J2224-0158, returning a C/O ratio consistent with previous fits to the same JHK  s  data, but disagreeing in the thermal structure, cloud properties, and atmospheric scale height. For HD 106906 b, we retrieve C/O $={0.53}_{-0.25}^{+0.15}$ , consistent with the C/O ratios expected for HD 106906's stellar association and therefore consistent with a stellar-like formation for the companion. We find abundances of H2O and CO near chemical equilibrium values for a solar metallicity but a surface gravity lower than expected, as well as a thermal profile with sharp transitions in the temperature gradient. Despite high signal-to-noise ratio and spectral resolution, more accurate constraints necessitate data across a broader wavelength range. This work serves as preparation for subsequent retrievals in the era of JWST, as JWST's spectral range provides a promising opportunity to resolve difficulties in fitting low-gravity L dwarfs and also underscores the need for simultaneous comparative retrievals on L-dwarf companions with multiple retrieval codes.

Keywords: Exoplanet atmospheric composition , Planetary atmospheres, L dwarfs, Exoplanet astronomy, Extrasolar gaseous planets, Exoplanet structure, Exoplanet formation, Exoplanet atmospheres, Atmospheric science
A Simultaneous Dual-site Technosignature Search Using International LOFAR Stations. The Search for Extraterrestrial Intelligence aims to find evidence of technosignatures, which can point toward the possible existence of technologically advanced extraterrestrial life. Radio signals similar to those engineered on Earth may be transmitted by other civilizations, motivating technosignature searches across the entire radio spectrum. In this endeavor, the low-frequency radio band has remained largely unexplored; with prior radio searches primarily above 1 GHz. In this survey at 110-190 MHz, observations of 1,631,198 targets from TESS and Gaia are reported. Observations took place simultaneously with two international stations (noninterferometric) of the Low Frequency Array in Ireland and Sweden. We can reject the presence of any Doppler drifting narrowband transmissions in the barycentric frame of reference, with equivalent isotropic radiated power of 1017 W, for 0.4 million (or 1.3 million) stellar systems at 110 (or 190) MHz. This work demonstrates the effectiveness of using multisite simultaneous observations for rejecting anthropogenic signals in the search for technosignatures.

Keywords: Exoplanets, Technosignatures, Astrobiology, Search for extraterrestrial intelligence, Radio astronomy
Accelerating Polyhedral Discrete Element Method with CUDA. This paper presents an efficient CUDA-based implementation of a nonspherical discrete element method where irregular particles are described by using polyhedrons. Two strategies are employed to exploit the parallelism of the numerical method. One is to perform contact detection based on the contact pair level instead of the traditional particle level. The second is to reduce the computational burden of each kernel function by allocating thread blocks reasonably. Contact detection between potential contact pairs is the most complicated, time-consuming, and essential process for the polyhedral discrete element method. The linear bounding volume hierarchies are introduced to fix this issue. The hierarchies of the bounding volume tree are organized in a spatially coherent way. Such a structure can minimize branch divergence and is very suitable for parallel implementation with GPU. Two numerical examples are presented to show the performance of the code. It is found from the scenario of two sphere collision that improving the mesh resolution of polyhedral particles can reduce the computational error while slowing down the computational speed correspondingly. A trade-off must be made between accuracy and efficiency. The other example of self-gravitating aggregation demonstrates the code is convergent, stable, and highly efficient. Particularly, with a mainstream GPU, the proposed method easily performs hundreds of times faster than the serial CPU code that does the same function.

Keywords: N-body problem, Astronomical simulations
Two Warm Super-Earths Transiting the Nearby M Dwarf TOI-2095. We report the detection and validation of two planets orbiting TOI-2095 (TIC 235678745). The host star is a 3700 K M1V dwarf with a high proper motion. The star lies at a distance of 42 pc in a sparsely populated portion of the sky and is bright in the infrared (K = 9). With data from 24 sectors of observation during Cycles 2 and 4 of the Transiting Exoplanet Survey Satellite, TOI-2095 exhibits two sets of transits associated with super-Earth-sized planets. The planets have orbital periods of 17.7 days and 28.2 days and radii of 1.30 R ⊕ and 1.39 R ⊕, respectively. Archival data, preliminary follow-up observations, and vetting analyses support the planetary interpretation of the detected transit signals. The pair of planets have estimated equilibrium temperatures of approximately 400 K, with stellar insolations of 3.23 and 1.73 S ⊕, placing them in the Venus zone. The planets also lie in a radius regime signaling the transition between rock-dominated and volatile-rich compositions. They are thus prime targets for follow-up mass measurements to better understand the properties of warm, transition-radius planets. The relatively long orbital periods of these two planets provide crucial data that can help shed light on the processes that shape the composition of small planets orbiting M dwarfs.

Keywords: Exoplanets, M stars
The High-energy Spectrum of the Young Planet Host V1298 Tau. V1298 Tau is a young pre-main-sequence star hosting four known exoplanets that are prime targets for transmission spectroscopy with current-generation instruments. This work pieces together observations from the NICER X-ray telescope, the Space Telescope Imaging Spectrograph and Cosmic Origins Spectrograph instruments aboard Hubble Space Telescope, and empirically informed models to create a panchromatic spectral energy distribution for V1298 Tau spanning 1─105 Å. We describe the methods and assumptions used to assemble the panchromatic spectrum and show that despite this star's brightness, its high-energy spectrum is near the limit of present X-ray and ultraviolet observatories' abilities to characterize. We conclude by using the V1298 Tau spectrum as a benchmark for the activity saturation stage of high-energy radiation from solar-mass stars to compare the lifetime cumulative high-energy irradiation of the V1298 Tau planets to other planets orbiting similarly massive stars.

Keywords: X-ray astronomy, Atmospheric evolution, Stellar chromospheres, Stellar magnetic fields, Ultraviolet astronomy, Pre-main sequence stars, Stellar coronae, Stellar atmospheres
Mitigating Worst-case Exozodiacal Dust Structure in High-contrast Images of Earth-like Exoplanets. Detecting Earth-like exoplanets in direct images of nearby Sun-like systems brings a unique set of challenges that must be addressed in the early phases of designing a space-based direct imaging mission. In particular, these systems may contain exozodiacal dust, which is expected to be the dominant source of astrophysical noise. Previous work has shown that it may be feasible to subtract smooth, symmetric dust from observations; however, we do not expect exozodiacal dust to be perfectly smooth. Exozodiacal dust can be trapped into mean-motion resonances with planetary bodies, producing large-scale structures that orbit in lock with the planet. This dust can obscure the planet, complicate noise estimation, or be mistaken for a planetary body. Our ability to subtract these structures from high-contrast images of Earth-like exoplanets is not well understood. In this work, we investigate exozodi mitigation for Earth-Sun-like systems with significant mean-motion resonant disk structures. We find that applying a simple high-pass filter allows us to remove structured exozodi to the Poisson noise limit for systems with inclinations &lt;60° and up to 100 zodis. However, subtracting exozodiacal disk structures from edge-on systems may be challenging, except for cases with densities &lt;5 zodis. For systems with three times the dust of the solar system, which is the median of the best fit to survey data in the habitable zones of nearby Sun-like stars, this method shows promising results for mitigating exozodiacal dust in future Habitable Worlds Observatory observations, even if the dust exhibits significant mean-motion resonance structure.

Keywords: Extrasolar rocky planets, Coronagraphic imaging, Habitable zone, Exozodiacal dust
ELemental abundances of Planets and brown dwarfs Imaged around Stars (ELPIS). I. Potential Metal Enrichment of the Exoplanet AF Lep b and a Novel Retrieval Approach for Cloudy Self-luminous Atmospheres. AF Lep A+b is a remarkable planetary system hosting a gas-giant planet that has the lowest dynamical mass among directly imaged exoplanets. We present an in-depth analysis of the atmospheric composition of the star and planet to probe the planet's formation pathway. Based on new high-resolution spectroscopy of AF Lep A, we measure a uniform set of stellar parameters and elemental abundances (e.g., [Fe/H] = -0.27 ± 0.31 dex). The planet's dynamical mass ( ${2.8}_{-0.5}^{+0.6}$ M Jup) and orbit are also refined using published radial velocities, relative astrometry, and absolute astrometry. We use petitRADTRANS to perform chemically consistent atmospheric retrievals for AF Lep b. The radiative-convective equilibrium temperature profiles are incorporated as parameterized priors on the planet's thermal structure, leading to a robust characterization for cloudy self-luminous atmospheres. This novel approach is enabled by constraining the temperature-pressure profiles via the temperature gradient $(d\mathrm{ln}T/d\mathrm{ln}P)$ , a departure from previous studies that solely modeled the temperature. Through multiple retrievals performed on different portions of the 0.9-4.2 μm spectrophotometry, along with different priors on the planet's mass and radius, we infer that AF Lep b likely possesses a metal-enriched atmosphere ([Fe/H] &gt; 1.0 dex). AF Lep b's potential metal enrichment may be due to planetesimal accretion, giant impacts, and/or core erosion. The first process coincides with the debris disk in the system, which could be dynamically excited by AF Lep b and lead to planetesimal bombardment. Our analysis also determines T eff ≈ 800 K, $\mathrm{log}(g)\approx 3.7$ dex, and the presence of silicate clouds and disequilibrium chemistry in the atmosphere. Straddling the L/T transition, AF Lep b is thus far the coldest exoplanet with suggested evidence of silicate clouds.

Keywords: Exoplanet atmospheric composition , Stellar abundances, Exoplanet formation, Extrasolar gaseous giant planets, Exoplanet atmospheres
The Prospect of Detecting Volcanic Signatures on an ExoEarth Using Direct Imaging. The James Webb Space Telescope (JWST) has provided the first opportunity of studying the atmospheres of terrestrial exoplanets and estimating their surface conditions. Earth-sized planets around Sun-like stars are currently inaccessible with JWST, however, and will have to be observed using the next generation of telescopes with direct-imaging capabilities. Detecting active volcanism on an Earth-like planet would be particularly valuable as it would provide insight into its interior and provide context for the commonality of the interior states of Earth and Venus. In this work, we used a climate model to simulate four exoEarths over eight years with ongoing large igneous province eruptions with outputs ranging from 1.8 to 60 Gt of sulfur dioxide. The atmospheric data from the simulations were used to model direct-imaging observations between 0.2 and 2.0 μm, producing reflectance spectra for every month of each exoEarth simulation. We calculated the amount of observation time required to detect each of the major absorption features in the spectra, and we identified the most prominent effects that volcanism had on the reflectance spectra. These effects include changes in the size of the O3, O2, and H2O absorption features and changes in the slope of the spectrum. Of these changes, we conclude that the most detectable and least ambiguous evidence of volcanism are changes in both O3 absorption and the slope of the spectrum.

Keywords: Exoplanets, Exoplanet astronomy, Direct imaging, Spectroscopy, Exoplanet detection methods, Exoplanet atmospheres, Volcanism