Sazuna/UAT_keywords huggingface dataset:
Rigid-body Numerical Integration of Io's Physical Libration Under Multibody Perturbations. This study investigates the spin–orbit coupling of natural satellites, focusing on Io's libration as a means of probing its internal structure and tidal responses. The modeling of Io's libration incorporates the complexities of multibody perturbations and nonspherical gravitational fields. To address these challenges, a numerical framework is developed based on rigid-body dynamics, aiming to simulate Io's orbital and rotational motions and assess its internal structure and tidal effects. The model includes Jupiter's nonspherical gravitational field, perturbations from the Galilean satellites, and gravitational influences from the major planets. Orbital and rotational motions are integrated using a 15th-order Gauss–Radau integrator along with the Runge–Kutta–Fehlberg method. Simulation results demonstrate the reliability of the model: orbital errors remain within ±350 km and ±20 m s‑1, and the Euler angles closely match International Astronomical Union (IAU) reference data, effectively reproducing Io's rotational state. The libration components exhibit harmonic oscillations, with τ displaying a quasi-sawtooth pattern, aligning with values derived from IAU Euler angles. These results validate the rigid-body approximation and demonstrate the model's applicability to other satellite studies. The framework provides a foundation for internal structure inversion, tidal dissipation analysis, and future mission planning.

Keywords: Libration, Planetary dynamics, Io, Planetary interior, N-body simulations
NutMaat: A Python Package for Stellar Spectral Classification on the MK System. Stellar spectral classification according to the Morgan─Keenan (MK) system remains fundamental to astrophysical studies, yet modern surveys require automated, scalable tools. We present NutMaat, an open-source Python-based package inspired by MKCLASS, designed to automate MK classification while addressing scalability and usability limitations. It employs modern computational tools for batch processing and offers a modular architecture that enables efficient, platform-independent analysis of large spectral data sets. It also includes modules for detecting classical chemically peculiar stars, such as Am, Ap, and λ Boo types, using internal consistency checks between different line diagnostics. Tested on the CFLIB and MILES libraries, NutMaat achieved spectral and luminosity classification accuracies comparable to MKCLASS, with minimal systematic offsets and a robust performance down to a signal-to-noise ratio ≲ 10. NutMaat successfully identified chemically peculiar stars, tested on LAMOST DR7 ACV variables, and processed the SDSS-IV MaStar library—which lacks native MK classifications—to produce a stellar catalog, demonstrating survey readiness. Future development of NutMaat will focus on extending wavelength coverage beyond the 3800─5600 Å range, computational acceleration via Cython, and refining peculiarity classification. Beyond its technical design, NutMaat can provide consistent, MK-standard classification across large-scale spectroscopic surveys, facilitating reliable stellar population analyses, identification of rare objects, and the construction of high-quality spectral catalogs essential for galactic archaeology and stellar evolution studies. As an open-source tool, NutMaat bridges traditional MK methods with modern data workflows, offering a scalable solution for current and future spectroscopic surveys.

Keywords: Open source software, Fundamental parameters of stars, Stellar classification, Stellar types, Spectroscopy, Chemically peculiar stars, Catalogs
The Watery Atmosphere of HD 209458 b Revealed by Joint K- and L-band High-resolution Spectroscopy. We present a joint analysis of high-resolution K- and L-band observations of the benchmark hot Jupiter HD 209458 b from the Keck Planet Imager and Characterizer. One half-night of observations was obtained in each bandpass, covering similar preeclipse phases. The two epochs were then jointly analyzed using our atmospheric retrieval pipeline based on petitRADTRANS to constrain the atmospheric pressure–temperature profile and chemical composition. Consistent with recent results from JWST observations at lower spectral resolution, we obtain an oxygen-rich composition for HD 209458 b (C/O &lt; 10‑3 at 95% confidence) and a lower limit on the volatile metallicity similar to the solar value ([(C + O)/H] &gt; ‑0.2 at 95% confidence). Leveraging the large spectral grasp of the multiband observations, we constrain the atmospheric H2O mixing ratio to  logH2OV MR&gt;‑3.1  at 95% confidence, and obtain 95% upper limits on the atmospheric mixing ratios of CO (&lt;10‑4.8), CH4 (&lt;10‑4.5), NH3 (&lt;10‑5.8), H2S (&lt;10‑3.3), and HCN (&lt;10‑5.6). The limits on CH4, NH3, and HCN are consistent with recent results from JWST transmission spectroscopy, demonstrating the value of multiband, ground-based high-resolution spectroscopy for precisely constraining trace-species abundances in exoplanet atmospheres. The retrieved low-C/O, moderate-metallicity composition for HD 209458 b is consistent with formation scenarios involving late accretion of substantial quantities of oxygen-rich refractory solids and/or ices.

Keywords: High resolution spectroscopy, Exoplanet atmospheric composition , Hot Jupiters, Exoplanet atmospheres
Simulation Analysis of Kinetic Impact Effects on Near-Earth Asteroid Defense Mission Using Precise Orbit Determination. The potential threat of near-Earth asteroid impacts on Earth has prompted global efforts to intensify research into asteroid defense technologies, and China plans to launch such a mission. Kinetic impact, as an effective defense method, changes the asteroid's trajectory to prevent a collision. However, the impact of kinetic energy on the asteroid's orbit is constrained by multiple factors, making the evaluation of the impact effects a challenge. This paper, set in the context of China's future inaugural asteroid defense mission, conducted a full-process asteroid orbit determination analysis and kinetic impact effect assessment. It analyzed the orbital accuracy of the target asteroid 2015 XF261 based on Earth-based observations, as well as the orbiting accuracy based on simulated observations from the "Observer" nearby the asteroid. In addition, in the phase of quantitative inversion analysis and evaluation after the kinetic impact, a velocity deviation of 1 mm s‑1 due to the kinetic impact on the asteroid is considered. Based on six months each of pre- and postimpact observation data from "Observer," an impact effect inversion with an accuracy of better than 0.0001 mm s‑1 can be achieved. Through high-precision orbit determination simulation analysis, this study provides important theoretical support for evaluating the effects of kinetic impact and lays a foundation for our national mission orbit analysis and the realization of scientific objectives.

Keywords: Near-Earth objects, Astronomy data analysis, Asteroid dynamics
Probing the Outskirts of M Dwarf Planetary Systems with a Cycle 1 JWST NIRCam Coronagraphy Survey. The population of giant planets on wide orbits around low-mass M dwarf stars is poorly understood, but the unprecedented sensitivity of JWST NIRCam coronagraphic imaging now provides direct access to planets significantly less massive than Jupiter beyond 10 au around the closest, youngest M dwarfs. We present the design, observations, and results of JWST Guaranteed Time Observation Program 1184, a Cycle 1 NIRCam coronagraphic imaging survey of nine very nearby and young low-mass stars at 3–5 μm wavelengths. In the F356W and F444W filters, we achieve survey median 5σ contrasts deeper than 10‑5 at a separation of 1″, corresponding to 0.20 MJup in F444W and 1.30 MJup in F356W at planet–star separations of 10 au. Our results include 3–5 μm debris disk detections and the identification of many extended and point-like sources in the final postprocessed images. In particular, we have identified a marginal point-source candidate having flux and color limits consistent with model predictions for a young sub-Jupiter-mass exoplanet. Under the assumption that the candidate is not confirmed, we place the first direct-imaging occurrence constraints on M dwarf wide-orbit (semimajor axes of 10–100 au), sub-Jupiter-mass exoplanets (0.3–1 MJup). We find frequency limits of &lt;0.10 and &lt;0.16 objects per star with 1σ and 3σ confidence, respectively. This survey showcases the unprecedented capabilities of JWST NIRCam coronagraphic imaging when targeting young, low-mass stars and acts as a precursor to broader surveys to place deep statistical constraints on wide-orbit, sub-Jupiter-mass planets around M dwarfs.

Keywords: Exoplanet astronomy, Coronagraphic imaging, Extrasolar gaseous planets, Direct imaging, Extrasolar ice giants
Possible Evidence for the Presence of Volatiles on the Warm Super-Earth TOI-270 b. The search for atmospheres on rocky exoplanets is a crucial step in understanding the processes driving atmosphere formation, retention, and loss. Past studies have revealed the existence of planets interior to the radius valley with densities lower than would be expected for pure-rock compositions, indicative of the presence of large volatile inventories, which could facilitate atmosphere retention. Here, we present an analysis of the JWST/NIRSpec G395H transmission spectrum of the warm ( Teq,AB=0=569  K) super-Earth TOI-270 b (Rp = 1.306 R⊕), captured alongside the transit of TOI-270 d. The JWST white light-curve transit depth updates TOI-270 b's density to ρp = 3.7 ± 0.5 g cm−3, inconsistent at 4.4σ with an Earth-like composition. Instead, the planet is best explained by a nonzero, percent-level water mass fraction, possibly residing on the surface or stored within the interior. The JWST transmission spectrum shows possible spectroscopic evidence for the presence of this water as part of an atmosphere on TOI-270 b, favoring an H2O-rich steam atmosphere model over a flat spectrum ( lnB=0.3─3.2 , inconclusive to moderate), with the exact significance depending on whether an offset parameter between the NIRSpec detectors is included. We leverage the transit of the twice-larger TOI-270 d crossing the stellar disk almost simultaneously to rule out the alternative hypothesis that the transit light source effect could have caused the water feature in TOI-270 b's observed transmission spectrum. Planetary evolution modeling furthermore shows that TOI-270 b could sustain a significant atmosphere on gigayear timescales, despite its high stellar irradiation, if it formed with a large initial volatile inventory.

Keywords: Exoplanet atmospheric composition , Exoplanet systems, Stellar activity, Exoplanet astronomy, Exoplanet evolution, Exoplanet atmospheres
Robust Data Interpretation for Perturbed Nulling Interferometers via Proper Handling of Correlated Errors. The detection and atmospheric characterization of potentially habitable, temperate terrestrial exoplanets using a space-based mid-infrared nulling interferometer is a major goal of contemporary astrophysics. A central part of the analysis of such an instrument is the treatment of correlated errors arising from perturbations in the system. While previous studies have often accounted for their effects in a limited manner, we aim to treat them comprehensively here, and we argue that data whitening based on the covariance of these errors is a suitable method to mitigate their impact. We present a framework that quantitatively connects instrumental perturbations to performance metrics, and we develop two computational tools to support our analysis: PHRINGE, for the generation of synthetic nulling data, and LIFESIMMC, a new Monte Carlo–based end-to-end simulator for the Large Interferometer For Exoplanets. Applying our framework to a reference observation of an Earth twin orbiting a Sun twin at 10 pc, we find that whitening is not only essential for a correct interpretation of the detection metric used in hypothesis testing, but also improves the estimates of the planetary properties. Moreover, our approach enables an estimation of the spectral covariance of the extracted planetary spectra, providing valuable additional input for future atmospheric retrievals. We therefore recommend incorporating the framework into performance assessments and requirement derivations for future nulling interferometers.

Keywords: Astronomy software, Monte Carlo methods, Direct detection interferometry, Exoplanet astronomy, Space telescopes, Astronomical simulations
Formation Process of the Young Stellar Population in Messier 16 from a Kinematic Perspective. We present a kinematic study of young stars in Messier 16 (M16) using the Gaia Data Release 3 and high-resolution spectra. A total of 345 stars are selected as genuine members using the published lists of X-ray sources, infrared sources, and early-type stars as well as the Gaia data. There is severe differential reddening across this region and the reddening law of the intracluster medium appears abnormal. The distance to M16, derived from the parallaxes of the members, is about 1.7 kpc. The ages of members, estimated by comparing their color─magnitude diagram with theoretical isochrones, range from 1 Myr to 4 Myr. This star-forming region is composed of an open cluster (NGC 6611) and a distributed population. This cluster shows a clear pattern of expansion and rotation. Some of the distributed population are spatially associated with the gas pillars located at the ridge of the H II bubble. In particular, several stars moving away from the cluster are physically associated with the northeastern pillar. In addition, their younger ages support the idea that their formation was triggered by the feedback from massive stars in NGC 6611. On the other hand, the other stars do not show systematic radial or stream motions; therefore, they likely formed through spontaneous star formation events. We discuss the formation of young stars in the context of cluster expansion, spontaneous star formation, and feedback-driven star formation, and suggest that possibly all of these mechanisms contributed.

Keywords: Stellar kinematics, Open star clusters, Star formation, Stellar associations
Searching for Planets Orbiting ϵ Eridani with JWST/NIRCam. We present observations of ϵ Eridani with the JWST/NIRCam coronagraph aimed at imaging planets orbiting within this system. In particular, these observations targeted (1) the Jupiter-like planet, first detected orbiting at 3.5 au with radial velocity observations, and (2) the planet postulated to be responsible for carving the edges of ϵ Eridani's outer ring, expected to orbit at 40─50 au. However, no point sources were detected at a statistically significant level. We report new, improved upper limits at 4 μm: ∼1 × 10−6 contrast at 1″, and ∼2 × 10−8 beyond 5″. The latter contrast limit precludes Saturn-mass planets at separations &gt;16 au given current models. We also report upper limits for ϵ Eridani's disk emission at 4 μm. While the radial surface brightness profile shows no evidence of emission, we detect a 1σ surface brightness signal on the east side of the system, consistent with forward scattering emission expected for ϵ Eridani's disk inclination. Finally, we evaluate the performance of the 3-roll observation strategy, which was first employed in these observations: the gains in contrast are modest, with 20%─30% improvements with respect to the conventional two-roll strategy.

Keywords: Exoplanet systems, Exoplanets, Circumstellar disks
Gas-phase Molecules in Protoplanetary Nebulae with the 21 μm Emission Feature. II. Carbon Monosulfide. The carrier of the 21 μm emission feature discovered in a handful of protoplanetary nebulae (PPNe) is one of the most intriguing enigmas in circumstellar chemistry. Investigating the gas-phase molecules in PPNe could yield important hints for understanding the 21 μm feature. In this paper, we report observations of the carbon monosulfide (CS) J = 5 → 4 line at 245 GHz and the CO J = 1 → 0 line at 115 GHz toward seven PPNe exhibiting the 21 μm feature. We find that CS is extremely scarce in these PPNe and the CS line is only detected in one source, IRAS Z02229+6208. Based on the assumption of local thermal equilibrium and negligible optical depth, we derive that the CS column densities and fractional abundances relative to H2 are N(CS) &lt; 9.1 × 1013 cm‑2 and f(CS) &lt; 8.1 × 10‑7. A comparison of the CS abundances across different circumstellar envelopes reveals that the variations in CS abundance are complex, depending not only on the evolutionary stages but also on the properties of individual objects.

Keywords: Molecular gas, Circumstellar envelopes, Protoplanetary nebulae, Circumstellar matter, Interstellar medium
Cocoon-to-butterfly Transformation in Protoplanetary Nebula: Detection of a Spherical Halo and a Barrel-shaped Torus in IRAS 06530–0213. Protoplanetary nebulae (PPNs) represent a critical evolutionary bridging stage between the asymptotic giant branch (AGB) and planetary nebula (PN) stages. Their dynamical structures provide key insights into late stellar evolution. Here, we report CO and 13CO imaging observations of the carbon-rich PPN IRAS 06530–0213, a source exhibiting the unidentified 21 μm emission band, conducted with the Northern Extended Millimeter Array. The CO maps reveal a spherical halo (diameter ∼10″) surrounding a central barrel-shaped torus, where the torus displays an inner diameter of  ∼1.″5  and an outer diameter of ∼2″. Through three-dimensional morpho-kinematic modeling with the SHAPE software, we determine that IRAS 06530–0213 experienced its final thermal pulse during the AGB phase ∼6500 yr ago, transitioning into the PPN phase ∼4500 yr ago. Our analysis indicates that the blueshifted CO emission, a feature also detected in several other PPNs and PNs previously misattributed to the interstellar clouds, actually originates from the obscuration of the central nebula by the remnant AGB halo. These findings are expected to deepen our understanding of the dynamical structures of PPNs, as well as their pivotal transitional role in the late-stage evolution of low-to-intermediate mass stars.

Keywords: Protoplanetary nebulae, Circumstellar matter, Stellar mass loss, Radio interferometers
NIR Filter Transformations Across the HR Diagram: JWST, Roman, and Euclid. We present new color transformations between select near-infrared filters on JWST/NIRCam, Euclid/NISP, Roman/WFI, HST, and ground-based izY+IJHKS, for a total of 105 unique filter combinations. Additionally, we apply these transformations to predict the color–magnitude relation of the tip of the red giant branch as seen with JWST, Euclid, and Roman based on theoretical results for Hubble Space Telescope and Two Micron All Sky Survey filters; for JWST we find good agreement with empirical results in the literature. We also find typical residual dispersion around these transformations of 0.01 mag for Cepheid and RR Lyrae variables and RGB stars, but up to 0.1 mag for O- and C-rich TP-AGB stars.

Keywords: Photometric systems, Stellar populations, Calibration, Stellar colors, Near infrared astronomy
ImageMM: Joint Multi-frame Image Restoration and Super-resolution. A key processing step in ground-based astronomy involves combining multiple noisy and blurry exposures to produce an image of the night sky with an improved signal-to-noise ratio. Typically, this is achieved via image coaddition, and can be undertaken such that the resulting night sky image has enhanced spatial resolution. Yet, this task remains a formidable challenge despite decades of advancements. In this paper, we introduce ImageMM: a new framework based on the majorization–minimization (MM) algorithm for joint multi-frame astronomical image restoration and super-resolution. ImageMM uses multiple registered astronomical exposures to produce a nonparametric latent image of the night sky, prior to the atmosphere's impact on the observed exposures. Our framework also features a novel variational approach to compute refined point-spread functions of arbitrary resolution for the restoration and super-resolution procedure. Our algorithms, implemented in TensorFlow, leverage graphics processing unit acceleration to produce latent images in near real time, even when processing high-resolution exposures. We tested ImageMM on Hyper Suprime-Cam (HSC) exposures, which are a precursor of the upcoming imaging data from the Rubin Observatory. The results are encouraging: ImageMM produces sharp latent images, in which spatial features of bright sources are revealed in unprecedented detail (e.g., showing the structure of spiral galaxies), and where faint sources that are usually indistinguishable from the noisy sky background also become discernible, thus pushing the detection limits. Moreover, aperture photometry performed on the HSC pipeline coadd and ImageMM's latent images yielded consistent source detection and flux measurements, thereby demonstrating ImageMM's suitability for cutting-edge photometric studies with state-of-the-art astronomical imaging data.

Keywords: GPU computing, Algorithms, Ground-based astronomy, Astronomy image processing
Strong NUV Refractory Absorption and Dissociated Water in the Hubble Transmission Spectrum of the Ultra Hot Jupiter KELT-20 b. Ultra-hot Jupiters (UHJs) present a promising pathway for drawing a link between a planet's composition and formation history. They retain both refractory and volatiles species in gas phase in their atmospheres, which allows us to place unique constraints on their building blocks. Here, we present the 0.2─1.7 μm transmission spectrum of KELT-20 b/MASCARA-2 b taken with the Hubble Space Telescope (HST). Unlike other UHJs around early-type stars, KELT-20 b's orbit is well aligned with its host star's spin axis, and we test whether its distinct dynamical configuration is reflected in its composition. We observe a tremendous rise (&gt;10 scale heights) in the planet's transit depth at the near-UV (NUV) wavelengths, akin to that observed for WASP-178 b and WASP-121 b, and a muted water absorption feature in the near-IR. Our retrievals indicate that the large NUV depth is driven by Fe II and/or SiO and that the water is mostly thermally dissociated. Assuming equilibrium chemistry, we obtain constraints on Z/H and O/H that indicate accretion of volatile-rich solids and/or gas. Both our low-resolution spectrum and the refractory elemental ratios from S. Gandhi et al. suggest that nightside condensation and rainout are limited to only the most refractory species in the planet's atmosphere. Within the precision limits of the HST spectra, no strong evidence for limb asymmetry is detected. We contextualize this lack of asymmetry by comparing to predictions from general circulation models with and without the effects of kinematic magnetohydrodynamics. Lastly, we find no major differences in the HST transmission spectra of KELT-20 b, WASP-178, and WASP-121 b despite their different dynamical configurations.

Keywords: Atmospheric composition, Hot Jupiters, Planet formation, Exoplanet atmospheres