Sazuna/UAT_keywords huggingface dataset:
Toward Robustness across Cosmological Simulation Models ILLUSTRISTNG, SIMBA, ASTRID, and SWIFT-EAGLE. The rapid advancement of large-scale cosmological simulations has opened new avenues for cosmological and astrophysical research. However, the increasing diversity among cosmological simulation models presents a challenge to the robustness. In this work, we develop the Model-Insensitive ESTimator (MIEST), a machine that can robustly estimate the cosmological parameters, Ωm and σ8, from neural hydrogen maps of simulation models in the Cosmology and Astrophysics with MachinE Learning Simulations project—ILLUSTRISTNG, SIMBA, ASTRID, and SWIFT-EAGLE. An estimator is considered robust if it possesses a consistent predictive power across all simulations, including those used during the training phase. We train our machine using multiple simulation models and ensure that it only extracts common features between the models while disregarding the model-specific features. This allows us to develop a novel model that is capable of accurately estimating parameters across a range of simulation models, without being biased toward any particular model. Upon the investigation of the latent space—a set of summary statistics, we find that the implementation of robustness leads to the blending of latent variables across different models, demonstrating the removal of model-specific features. In comparison to a standard machine lacking robustness, the average performance of MIEST on the unseen simulations during the training phase has been improved by ∼17% for Ωm and 38% for σ8. By using a machine learning approach that can extract robust, yet physical features, we hope to improve our understanding of galaxy formation and evolution in a (subgrid) model-insensitive manner, and ultimately, gain insight into the underlying physical processes responsible for robustness.

Keywords: Hydrodynamical simulations, Cosmological evolution, Cosmological parameters, Convolutional neural networks, Cosmological parameters from large-scale structure, Robust regression, Galaxy evolution
Metal-enriched Atmospheres in Warm (Super- and Sub-) Neptunes Induced by Extreme Atmospheric Escape. Planet formation impacts exoplanet atmospheres by accreting metals in solid form, leading to atmospheric carbon-to-oxygen ratios (C/O) and sulfur-to-nitrogen ratios (S/N) that deviate from those of their host stars. Recent observations indicate differing metal abundances in planetary atmospheres compared to their stellar companions. However, these observations are biased toward mature planets, raising questions about whether these abundances result from formation or evolved over time. Another way to alter an atmosphere is through the escape of particles due to thermal heating. This study examines how billions of years of particle escape affect metal abundances. Using an adjusted stellar evolution code incorporating hydrodynamic escape, we model a warm (Teq ≍ 1000 K) super-Neptune-type planet (Mini = 26M⊕) orbiting a solar-type star. Our results show increased metal-to-hydrogen abundances of ∼50─70 × initial enrichment after 10 Gyr. We also see a 0.88 × decrease in C/O abundance and a 1.27 × increase in S/N abundance, which can affect the interpretation of planet formation parameters. We also simulate the evolving atmosphere using chemical kinetics and radiative transfer codes, finding substantial increases in SO2, CO2, and H2O abundances and a decrease in CH4 abundance. These changes are easily observable in the IR wave band transmission spectrum. Our findings demonstrate that extreme escape of lighter particles significantly influences the evolution of warm Neptunes and complicates the interpretation of their observational data. This highlights the need to consider long-term atmospheric evolution in understanding exoplanet compositions.

Keywords: Exoplanet evolution, Hydrodynamics, Exoplanets, Exoplanet atmospheric evolution
IBEX Observations of Elastic Scattering of Interstellar Helium by Solar Wind Particles. The IBEX-Lo instrument on the Interstellar Boundary Explorer (IBEX) mission observes primary and secondary interstellar helium in its four lowest energy steps. Observations of these helium populations have been analyzed and compared to simulations using the analytic full integration of neutrals model. A systematic difference is observed between the simulations and observations of secondary helium during solar cycle (SC) 24. We show that elastic scattering of primary helium by solar wind protons, which redistributes atoms from the core of the primary helium flux distribution, provides an explanation of the observed divergence from simulations. We test the validity of this explanation by showing that the elastic scattering also forms a halo in the wings of the primary helium distribution in the spin-angle plane. Correcting the simulation for the effects of elastic scattering requires an increase of the estimated density of primary helium, compared to previous estimates by Ulysses/GAS. The combined density of interstellar helium, derived from the previous studies, has been recalculated to be 0.0153 ± 0.0011. Based on our analysis of IBEX observations and χ2 minimization of simulation data that include the effects of elastic scattering, any estimation of neutral interstellar helium density at 1 au by direct detection of the peak flux of neutral helium needs to be adjusted by ∼12%.

Keywords: Photoionization, Heliosphere, Pickup ions, Interstellar medium, Solar activity
Exploring the Frontiers of Cosmic-Ray Physics: Perspectives on GRANDProto300 and the GRAND Project. The Giant Radio Array for Neutrino Detection (GRAND) is an envisioned large-scale radio array designed to detect ultrahigh-energy cosmic rays (UHECRs, E &gt; 100 PeV) and neutrinos. Employing cost-effective radio antennas distributed across vast areas, GRAND is optimized to observe the rare flux of ultrahigh-energy particles with high precision. The GRANDProto300 (GP300) pathfinder array, currently under deployment, targets the 1016.5–1018 eV range and is anticipated to achieve approximately 15% energy resolution and 20 g cm‑2  Xmax  precision. This level of precision enables accurate measurements of the fine structure of the energy spectrum, mean logarithmic mass ( &lt;lnA&gt; ), and proton flux within this energy range for GP300. After 5 yr of data collection, the sensitivity for detecting anisotropy could reach 5 × 10‑3 for energies below 1017.1 eV. With its substantially larger effective area, GRAND extends these capabilities to the highest energies (∼1020 eV), offering enhanced statistics and sensitivity for spectral, composition, and anisotropy measurements within 1 yr for UHECRs.

Keywords: Particle astrophysics, Cosmic ray detectors, Ultra-high-energy cosmic radiation, Cosmic rays
Mantis Shrimp: Exploring Photometric Band Utilization in Computer Vision Networks for Photometric Redshift Estimation. We present Mantis Shrimp, a multisurvey deep learning model for photometric redshift estimation that fuses ultraviolet (Galaxy Evolution Explorer), optical (PanSTARRS), and infrared (UnWISE) imagery. Machine learning is now an established approach for photometric redshift estimation, with generally acknowledged higher performance in areas with a high density of spectroscopically identified galaxies over template-based methods. Multiple works have shown that image-based convolutional neural networks can outperform tabular-based color/magnitude models. In comparison to tabular models, image models have additional design complexities: It is largely unknown how to fuse inputs from different instruments that have different resolutions or noise properties. The Mantis Shrimp model estimates the conditional density estimate of redshift using cutout images. The density estimates are well calibrated, and the point estimates perform well in the distribution of available spectroscopically confirmed galaxies with (bias = 1e-2), scatter (NMAD = 2.44e-2), and catastrophic outlier rate (η&gt;0.15 = 4.51%). We find that early-fusion approaches (e.g., resampling and stacking images from different instruments) match the performance of late-fusion approaches (e.g., concatenating latent space representations), so that the design choice ultimately is left to the user. Finally, we study how the model learns to use information across bands, finding evidence that our model successfully incorporates information from all surveys. The applicability of our model to the analysis of large populations of galaxies is limited by the speed and ease of downloading and preparing cutouts from external servers; however, our model could be useful in smaller studies such as in generating priors over redshift for stellar population synthesis.

Keywords: Astronomy data analysis, Redshift surveys, Neural networks
Searching for Accreting Compact Object Binaries in SRG/eROSITA eRASS1. Compact object binaries with accreting white dwarfs, neutron stars, or black holes are crucial for understanding accretion physics. In this study, we identify accreting compact object binary candidates in the Spectrum─Roentgen─Gamma/eROSITA eRASS1 by combining their X-ray fluxes with Gaia photometry and Zwicky Transient Facility (ZTF) time-domain observations. Candidates are selected based on their location in the "X-ray Main Sequence," a diagram incorporating their X-ray-to-optical flux ratios and optical colors, which suggest accretion-driven X-ray emission. We identify 22 candidates in the eRASS1 catalog using a three-step selection process: (1) cross-matching to a unique Gaia optical counterpart within a 10″ radius; (2) requiring X-ray-to-optical flux ratios exceeding the "X-ray Main Sequence"; and (3) detecting short-period variability in ZTF time-domain photometry. The resulting 22 candidates, including two previously confirmed compact object binaries, represent promising candidates for spectroscopic follow-up to confirm their accreting nature. Our results demonstrate the effectiveness of combining X-ray-to-optical flux ratios and optical colors jointly with time-domain photometry to uncover accreting compact object binaries. The approach is scalable and adaptable to future multiwavelength sky surveys, offering a promising path toward a more complete census of compact object binaries in the Galaxy.

Keywords: X-ray binary stars, Light curves, Photometry, Compact objects, Cataclysmic variable stars
Effect of Nonuniform Parallel Magnetic Field on the Kelvin–Helmholtz Instability in the Orion Nebula. The surface rippled structures of Orion molecular cloud have been attributed to the Kelvin–Helmholtz (KH) instability, and the influence of magnetic field and pressure on the formation and evolution of these structures is one of the important issues that has been considered frequently in the dynamics of clouds. However, the effects of magnetic field inhomogeneity and compressibility variations are still underexplored. Here, the two-dimensional radiation magnetohydrodynamic simulations are performed to study the evolution of the KH instability in the Orion Nebula in the presence of a nonuniform magnetic field parallel to the flow direction. The results indicate that the rippled structures in the near Trapezium Cluster region are more pronounced. Also, the sound Mach number increases with decreasing gas pressure, enhancing the system compressibility and weakening the KH instability. And the position of the slow rarefaction layer, where the gas pressure is relatively weak, corresponds to that of the strong compression layer of the magnetic flux tube. Finally, it is found that the strong magnetic field gradient with small magnetic shear thickness between the HII region and the rippled region has a stabilizing effect on instability, which is a result of the increased magnetic field strength within the shear layer. Based on these results, it is preliminarily discussed that the magnetic field in the Orion Nebula is the key feedback process to regulate or stimulate the formation of stars, and the compressibility also affects the efficiency of the star formation.

Keywords: Magnetohydrodynamics, Hydrodynamics, Astrophysical fluid dynamics, Magnetic fields, Star clusters
Solar and Interplanetary Determinants of Long-term Solar Modulation of Cosmic-Ray Intensity for Median Rigidities of 11–107 GV. We investigate the long-term modulation of cosmic-ray (CR) intensity across median rigidities from 11 to 107 GV using over four decades (1980–2023) of data from neutron monitors (NMs) and muon detectors (MDs). The analysis incorporates global NM stations and the Nagoya Multi-Directional Muon Telescope to evaluate the influence of key heliospheric parameters: interplanetary magnetic field (IMF) strength, heliospheric current sheet tilt angle (TA), and solar wind (SW) speed. Results reveal pronounced rigidity-dependent modulation patterns. Lower-rigidity NMs exhibit stronger sensitivity to heliospheric conditions, driven largely by IMF and TA, consistent with diffusion- and drift-dominated transport. In contrast, higher-rigidity MDs show reduced modulation amplitudes, with IMF remaining the dominant influence and SW gaining relative importance as drift effects diminish. These findings provide new insight into the energy-dependent roles of heliospheric drivers in CR modulation and offer a robust framework for advancing space weather prediction and heliospheric transport modeling.

Keywords: Galactic cosmic rays, Solar-terrestrial interactions, Solar cycle
JWST-MIRI Observations of the Irradiated Chemistry in the Inner Disk Cavity of GM Aur. We present a spectroscopic analysis of the GM Aur disk using JWST MIRI-MRS, as part of the JWST Disk Infrared Spectral Chemistry Survey (JDISCS). The 1D spectrum exhibits faint dust continuum emission and is relatively poor in molecular gas compared to protoplanetary disks with no inner dust cavities. We identify fundamental CO emission, bright rotationally excited OH lines longward of 9 μm, weak rotational H2O emission, the methyl cation CH 3+ , HCO+, and tentatively identify CO2. Otherwise, the spectrum is dominated by H2 and atomic emission. We model the molecular spectra using slab models and retrieve excitation temperatures, column densities, and emitting areas in a Bayesian framework. The OH line fluxes are used to estimate the photodissociation rate of water. We find that 5.4 × 1040 H2O molecules are photodestroyed every second, which suggests that the highest-energy OH lines trace a region near the 0.2 au dust cavity wall with an incident far-ultraviolet flux of G0 ∼ 107. The OH emission is compared to DALI models, which point toward a high incident flux of Lyα photons in the OH emitting region. We further use the H I lines to provide an independent estimate of the accretion luminosity and mass accretion rate, in agreement with prior measurements. A comparison with other cavity disks indicates that more evolved systems such as GM Aur may be less volatile rich and are characterized by brighter OH prompt emission and abundant molecular ions.

Keywords: Water vapor, Infrared spectroscopy, Planet formation, Photodissociation reactions, Astrochemistry, Classical T Tauri stars, James Webb Space Telescope, Protoplanetary disks, Ionization, Hydroxyl sources
Spatial Distribution of H<SUB>2</SUB>O<SUP>+</SUP> Ions in the Inner Coma of C/2014 Q2 (Lovejoy). Neutral molecules that sublimate from cometary ices (mainly water at ∼1 au from the Sun) are ionized due to solar extreme-ultraviolet radiation and collisions with highly energetic electrons. The primary ionization product of water is H2O+, which is rapidly converted into H3O+ through proton-transfer reaction with H2O in the inner coma. Ion-mass spectrometers on board spacecraft such as Giotto and Rosetta have measured H2O+ ions in the inner coma, while emission bands of H2O+ in the optical wavelength region can be observed from ground-based observatories. We present the spatial intensity distribution of the H2O+ emission in comet C/2014 Q2 (Lovejoy), derived from high-resolution spectra taken on UT 2015 January 11. The observations covered a projected distance of ∼3000 km across the sky along the slit, with a spatial resolution of ∼200 km resulting from the atmospheric seeing. The observed H2O+ profile scales as  ρ‑0.13  (where  ρ  is the projected distance from the nucleus), in contrast to the  ρ‑1  profile seen in sunlight reflected by dust grains. We modeled the intensity profile of H2O+ using a steady-state, radially expanding coma model. Our results indicate that the proton-transfer reaction of H2O+ with H2O dominates the loss process of H2O+ in the inner coma. Assuming that H2O+ is produced primarily by photoionization of H2O, the modeled intensity profile of H2O+ remains constant, which is inconsistent with our observations. However, when an electron-impact ionization frequency inversely proportional to distance from the nucleus is assumed, the model successfully reproduces the observed profile.

Keywords: Neutral coma gases, Ionized coma gases, Comets, Comae
The Compact Object and Innermost Ejecta of SN 1987A. The first JWST observations of SN 1987A provided clear evidence that a compact object is ionizing the innermost ejecta. Here, we analyze a second epoch of JWST NIRSpec and MIRI/Medium-Resolution Spectrometer observations to better characterize the properties of this region, aided by a higher spectral resolving power for the new NIRSpec data. We confirm the presence of the previously identified narrow lines from the central region, i.e., ([Ar VI] 4.5292 μm, [Ar II] 6.9853 μm, [S IV] 10.5105 μm, and [S III] 18.7130 μm), and also identify similar components in [Ca V] 4.1585 μm, [Cl II] 14.3678 μm, and possibly [Fe II] 1.6440 μm. These lines are blueshifted by ∼−250 km s−1, while the emission region is spatially unresolved and located southeast of the center. The offset and blueshift could imply a kick velocity of 510 ± 55 km s−1 for the neutron star. We also identify [Ca IV] 3.2068 μm near the center, but it is displaced to the north and has a redshift of ∼700 km s−1. We find that scattering by dust in the ejecta with a typical grain size ∼0.3 μm can explain the [Ca IV] properties and the absence of other narrow lines at shorter wavelengths, while dust absorption is important at λ ≳ 8 μm. Photoionization models for a pulsar wind nebula and a cooling neutron star are both compatible with the observations, with the exception of the [Fe II] feature. The two models primarily differ at short wavelengths, where new lines are expected to emerge over time as the optical depth of dust in the expanding ejecta decreases.

Keywords: Neutron stars, Dust physics, Core-collapse supernovae, Pulsars, Supernova remnants
Environmental Effects in Stellar Mass Gravitational-wave Sources. I. Expected Fraction of Signals with Significant Dephasing in the Dynamical and Active Galactic Nucleus Channels. We present the first overview of the expected quantity of signals that will showcase significant gravitational-wave phase shifts caused by astrophysical environments, considering the upcoming A+ and A# LIGO/Virgo/KAGRA, Cosmic Explorer, and Einstein Telescope detectors. We construct and analyze two general families of dephasing prescriptions with extensions to eccentric sources, as well as collect five specific prescriptions for the fundamental smoking gun physical mechanisms at play in the dynamical and active galactic nucleus formation channel for stellar mass binary black holes: Roemer delays, tidal forces, and hydrodynamical interactions. We compute the expected fraction of signals containing astrophysical dephasing, as a function of environmental properties and based on observed distributions of binary parameters. We find that next generation detectors can expect to find environmental effects in hundreds of detected signals.

Keywords: Gravitational wave astronomy, LIGO, Gravitational wave sources, Astrophysical black holes
Properties of Free-floating Planets Ejected through Planet─Planet Scattering. Multiple studies show that planet─planet scattering plays a key role in the dynamical evolution of planetary systems. It can also contribute to the census of free-floating planets. In this work, we run an ensemble of N-body simulations and record the properties of ejected planets. Our simulations sample a wide range of orbital and physical parameters. We find that 40%─80% of planets are ejected, depending on the initial number in the system. Most ejections occur over ∼108─109 yr. The mean excess velocity of ejected planets lies in the range 2─6 km s−1 relative to the host star, and strongly depends on the semimajor axis of the innermost planet. Regardless of initial location, all planets are equally likely to be ejected. Bound and ejected planets show distinct mass distributions, with bound planets being more massive. Increasing planetary radii reduces the ejection fraction due to higher collision rates. The properties of ejected planets do not strongly depend on initial spacing, though ejection timescales increase with separation. The ejection fraction is also largely insensitive to the distance from the host star used to define unbound status. Comparing our results with observed free-floating planet populations, we conclude that fewer than five Jovian-mass planets need to form per star to match observations—consistent with current constraints from both observations and planet formation models.

Keywords: Gravitational microlensing, Free floating planets, Exoplanets, Dynamical evolution
Very Late-time JWST and Keck Spectra of the Oxygen-rich Supernova 1995N. We present new JWST/MIRI Medium Resolution Spectroscopy and Keck spectra of SN 1995N obtained in 2022─2023, more than 10,000 days after the supernova (SN) explosion. These spectra are among the latest direct detections of a core-collapse SN, both through emission lines in the optical and thermal continuum from infrared (IR) dust emission. The new IR data show that dust heating from radiation produced by the ejecta interacting with circumstellar matter is still present but greatly reduced from when SN 1995N was observed by the Spitzer Space Telescope and WISE in 2009/2010 and 2018, when the dust mass was estimated to be 0.4 M⊙. New radiative-transfer modeling suggests that the dust mass and grain size may have increased between 2010 and 2023. The new data can alternatively be well fit with a dust mass of 0.4 M⊙ and a much reduced heating source luminosity. The new late-time spectra show unusually strong oxygen forbidden lines, stronger than the Hα emission. This indicates that SN 1995N may have exploded as a stripped-envelope SN, which then interacted with a massive H-rich circumstellar shell, changing it from intrinsically Type Ib/c to Type IIn. The late-time spectrum results when the reverse shock begins to excite the inner H-poor, O-rich ejecta. This change in the spectrum is rarely seen but marks the start of the transition from SN to SN remnant.

Keywords: Type II supernovae, Late stellar evolution, Dust formation
Revealing the Nature of Long-period Transients with Space-based Gravitational-wave Interferometers. A few members of the recently discovered class of long-period transients have been identified as binaries with white-dwarf primaries. In most cases, however, electromagnetic data are inconclusive, and isolated magnetars or compact binaries remain viable. If the pulsation period matches that of the orbit—as is the case for ILT J1101+5521 and GLEAM-X J0704–37—some of these elusive radio transients could be gravitational-wave bright in the mHz band. Space-based interferometers could thus be used to provide independent constraints on their nature. We quantify the signal-to-noise ratio for the known systems under various scenarios and show that a few could be detectable for sufficiently large chirp masses. Astrophysical implications for (non)detections are discussed.

Keywords: Gravitational wave astronomy, Compact objects, Radio transient sources