Sazuna/UAT_keywords huggingface dataset:
Is Dark Energy Changing? Probing the Universe's Expansion with Present and Future Astronomical Probes. This study explores the possibility of a time-varying dark energy (DE) equation of state (EoS) deviating from −1. We employ a comprehensive data set of the usual astronomical probes (Type Ia supernovae, baryon acoustic oscillations, Big Bang nucleosynthesis, Hubble data, and Planck 2018 cosmic microwave background (CMB)) alongside future mock gravitational wave (GW) distance measurements from the Einstein Telescope. We utilize the Padé approximation, a versatile framework encompassing well-known DE models such as constant EoS, Chevallier─Polarski─Linder parameterization, and other time-evolving DE parameterizations. Within the Padé parameterization, we examine three specific forms (Padé-I, SPadé-I, Padé-II) applied to both spatially flat and nonflat universes. Padé-II exhibits particularly interesting features in terms of the evidence of dynamical DE at many standard deviations. Our results can be summarized as follows. Flat universe: when analyzing the combined data set of standard probes (including CMB) with Padé-II in a flat universe, we find a strong preference (6.4σ) for a dynamical (time-varying) DE EoS. This preference remains significant (4.7σ) even when incorporating future GW data. Nonflat universe: in a nonflat universe, the combined standard data sets (without or with CMB) also indicate a dynamical DE EoS at a high confidence level (6.2σ and 6.4σ, respectively). The addition of GW data slightly reduces the evidence (3.8σ and 5.1σ, respectively), but the preference persists. These results collectively suggest a robust case for dynamical DE in the dark sector. While a nonflat universe is not strongly favored, Padé-II hints at a possible closed universe when CMB data are included (with or without GW data).

Keywords: Cosmology, Cosmological models, Cosmological parameters, Hubble constant, Dark energy
Abundance Pattern Fitting with Bayesian Inference: Constraining First Stars' Properties and Their Explosion Mechanism with Extremely Metal-poor Stars. The abundance patterns of extremely metal-poor stars preserve a fossil record of the Universe's earliest chemical enrichment by the supernova explosions from the evolution of first generation of stars, also referred to as Population III stars. By applying Bayesian inference to the analysis of abundance patterns of these ancient stars, this study presents a systematic investigation into the properties and explosion mechanism of Pop III stars. We apply NLTE corrections to enhance the reliability of abundance measurements, which significantly reduces the discrepancies in abundances between observations and theoretical yields for odd-Z elements, such as Na and Al. Our Bayesian framework also enables the incorporation of explodability and effectively mitigates biases introduced by varying resolutions across different supernova model grids. In addition to confirming a top-heavy (α = 0.54) initial mass function for massive Pop III stars, we derive a robust mass─energy relation (E ∝ M2) of the first supernovae. These findings demonstrate that stellar abundance analysis provides a powerful and independent approach for probing early supernova physics and the fundamental nature of the first stars.

Keywords: Stellar mass functions, Stellar abundances, Population III stars, Core-collapse supernovae
On the Origin of ∼100 TeV Neutrinos from the Seyfert Galaxy NGC 7469. The origin of TeV─PeV neutrinos detected by IceCube remains largely unknown. The most significant individual neutrino source is the Seyfert galaxy NGC 1068 with a soft spectrum. Another notable candidate is the Seyfert galaxy NGC 7469, which has been recently proposed as a potential neutrino emitter. The likelihood fit of the IceCube data for this source returned a hard spectral index of ∼1.9, and the excess is dominated by two high-energy events. The energies of these two neutrinos are estimated to be 100─200 TeV, implying a maximum proton energy  Ep,max&gt;2PeV , significantly higher than that in NGC 1068. In this paper, we analyze the Fermi Large Area Telescope observations of NGC 7469, which yield nondetection. The size of the neutrino-emitting region can be constrained by the nondetection when the neutrino flux takes a high value in the allowed range. We suggest that cosmic-ray protons are accelerated to PeV energies via turbulence or magnetic reconnection in the corona and produce ∼100─200 TeV neutrinos via the pγ process. In the turbulence acceleration scenario, the required maximum proton energy can be achieved with a magnetization parameter of σ ∼ 1, while in the reconnection scenario, a magnetization parameter with σ ∼ 10 is needed. In both scenarios, a pair-dominated composition for the corona is preferred. The difference in the neutrino spectrum between NGC 7469 and NGC 1068 could be due to a different magnetization parameter despite the fact that they belong to the same type of active galactic nucleus.

Keywords: Neutrino astronomy, Seyfert galaxies, Active galactic nuclei
Rotational Evolution of Deformed Magnetized Neutron Stars: Implications for Obliquity Distribution and Braking Indices Statistics. The rotational evolution of a strongly magnetized neutron star (NS), accreting or isolated, is driven by external torques of different nature. In addition to the torques, even the tiniest deformations of the NS crust can affect its rotation through asymmetries in its inertia tensor. Several factors may be responsible for the deformations, including strong magnetic fields, internal stresses, or local heating. The main effect produced by the deformations is the so-called free precession: the motion of the rotational axis with respect to the crust. We consider the evolution of a triaxially deformed isolated NS with a strong dipolar magnetic field for a broad range of parameters, taking into account the magnetic field decay. We show that the combination of pulsar torques and free precession results in a considerable broadening of the distribution of magnetic obliquity angles (the angle between the magnetic and rotational axes) and creates a population of objects where the rotational axis does not align with the magnetic axis at all but enters a limit-cycle regime. The combination of free precession and magnetic torques can also explain the observed distribution in pulsar braking indices by creating a periodic oscillation in the magnetic obliquity.

Keywords: Neutron stars, Magnetic fields, High energy astrophysics, Pulsars
Robustness Analysis of USmorph. I. Generalization Efficiency of Unsupervised Strategies and Supervised Learning in Galaxy Morphological Classification. We conduct a systematic robustness analysis of the hybrid machine learning framework USmorph, which integrates unsupervised and supervised learning for galaxy morphological classification. Although USmorph has already been applied to nearly 100,000 I-band galaxy images in the COSMOS field (0.2 &lt; z &lt; 1.2, Imag &lt; 25), the stability of its core modules has not been quantitatively assessed. Our tests show that the convolutional autoencoder achieves the best performance in preserving structural information when adopting an intermediate network depth, 5 × 5 convolutional kernels, and a 40D latent representation. The adaptive polar coordinate transform effectively enhances rotational invariance and improves the robustness of downstream tasks. In the unsupervised stage, a bagging clustering number of K = 50 provides the optimal trade-off between classification granularity and labeling efficiency. For supervised learning, we employ GoogLeNet, which exhibits stable performance without overfitting. We validate the reliability of the final classifications through two independent tests: (1) the t-distributed stochastic neighbor embedding visualization reveals clear clustering boundaries in the low-dimensional space; and (2) the morphological classifications are consistent with theoretical expectations of galaxy evolution, with both true and false positives showing unbiased distributions in the parameter space. These results demonstrate the strong robustness of the USmorph algorithm, providing guidance for its future application to the China Space Station Telescope mission.

Keywords: Astrostatistics techniques, Galaxy structure, Astronomy data analysis
The VISCACHA Survey XV: Tracing the 3D Structure and Chemical Evolution of the Outskirts of the Large Magellanic Cloud from Star Clusters. The Large Magellanic Cloud (LMC) is the Milky Way's most massive satellite. Its interactions with the Small Magellanic Cloud are expected to leave imprints on its structure and evolution. In this work, we use the LMC outer star cluster population to seek possible evidence imprinted in the LMC stellar population by presenting the ages, metallicities, and distances of 85 stellar clusters in the LMC outskirts, determined using statistical isochrone fitting applied to high-quality photometric data from the VISCACHA Survey. From the distances, we analyze their 3D distribution, which allows us to observe the counterpart of the southwestern warp previously inferred from red clump stars, as well as determine that eastern clusters are closer to us than the LMC's disk. From the ages and metallicities, we observe an overall homogeneous chemical evolution with two main exceptions: first, a metallicity dip is present in the northeast around 1 Gyr ago; second, the clusters' ages are more dispersed in the north of the galaxy, while in the remainder of the galaxy's periphery, we observe a positive azimuthal age gradient along the east─south─west direction. Furthermore, clusters older than 1.5 Gyr tend to be closer to the LMC plane. Such features can be connected to the past interactions between the Magellanic Clouds, particularly their more recent close encounters that are expected to have occurred between 1 and 2 Gyr and 250 Myr ago, which distort the external structure, trigger star formation, and potentially lead to the infall of metal-poor material into the LMC.

Keywords: Hertzsprung Russell diagram, Large Magellanic Cloud, Star clusters
ALMACAL. XV. Band 3 ALMA Survey and Number Counts. The Atacama Large Millimeter/submillimeter Array (ALMA) Calibrators (ALMACAL) project leverages ALMA maps of calibrator-centered fields to conduct deep millimeter/submillimeter surveys, enabling the detection of extragalactic sources with flux densities orders of magnitude fainter than achievable with other instruments. These faint sources are critical for refining evolutionary models, as their number counts provide key constraints. In this study, we analyzed Band 3 ALMACAL maps from 606 calibrator fields, employing a novel machine learning approach to mitigate the often-overlooked bias introduced by the calibrator itself. Supported by extensive simulations, we extended 100 GHz radio active galactic nucleus (AGN) counts by approximately 1.5 orders of magnitude in flux density and refined constraints on dusty star-forming galaxies, reaching sensitivities as low as ∼180 μJy. We have improved the sampling, compared to previous results, in the region of the dominant population transition (between dusty star-forming galaxies and radio AGN). Our results are in good agreement with model predictions.

Keywords: Active galaxies, Galaxy abundances, Galaxy photometry, Radio active galactic nuclei, Galaxies
Rest-frame Optical Spectroscopy of z ∼ 2 Quasars with Steep Hard X-Ray Spectral Shapes: X-Ray Selection of Super-Eddington Accretion and Verification. Super-Eddington accretion is a crucial phase in the growth of supermassive black holes. However, identifying super-Eddington accreting quasars observationally is challenging due to uncertain black-hole mass estimates and other complications. The Eddington ratio parameter does not accurately represent the accretion rate in the super-Eddington regime. On the other hand, super-Eddington accreting quasars appear to show large hard X-ray (rest-frame &gt; 2 keV) power-law photon indices, and they also exhibit distinct optical spectral features including weak [O III] λ5007 emission and strong Fe II emission. We test steep X-ray photon-index selection of super-Eddington accreting quasars by obtaining Palomar 200-inch Hale Telescope near-infrared (NIR) spectra for a pilot sample of nine Γ = 2.0─2.6 quasars at z ≍ 1.4─2.5. We derive Hβ-based single-epoch virial black-hole masses (median value 4.3 × 108 M⊙) and Eddington ratios (median value 0.6). The Eddington ratio distribution is consistent with that of the comparison sample, which is a flux-limited sample of quasars at z ≍ 1.5─3.5 with NIR spectroscopy. However, our super-Eddington candidates do show statistically weaker [O III] emission (Pnull = 0.0075) and marginally stronger Fe II emission (Pnull = 0.06). We also find one candidate with broad (width of 1960 km s−1) and blueshifted (690 km s−1) [O III] λ4959 and [O III] λ5007 lines, which probably originate from a strong [O III] outflow driven by super-Eddington accretion. Overall, the steep X-ray photon-index selection of super-Eddington accreting quasars appears promising. However, a larger sample is needed to further assess the reliability of the selection.

Keywords: Accretion, High energy astrophysics, Quasars, X-ray active galactic nuclei, X-ray quasars
From Underground Oceans to Continents: A Glimpse into the Water Inventory on Rocky Planets Using Host Star Abundances. The amount of surface water is thought to be critical for a planet's climate stability and thus habitability. However, the probability that a rocky planet may exhibit surface water at any point in its evolution is dependent on multiple factors, such as the initial water mass, geochemical evolution, and interior composition. To date, studies have examined the influence of interior composition on the water inventory of the planet or how surface oceans may be impacted by planet topography individually. Here, we provide the first exploration on the impact of interior composition, topography, and planet radius on the water inventory of rocky planets using a sample of 689 rocky planets with spectroscopically derived stellar abundances from APOGEE and GALAH. We find that the oxidation state of the mantle (FeO content) significantly impacts the mantle water storage capacity and potential for surface flooding. For an FeO ∼11 wt%, the water storage capacity of a 1 M⊕ is 2 times that of Earth, indicating that the oxidation state may reduce the amount of surface water. We quantify the impact of topography on seafloor pressures, showing that flat topographies are more likely to be flooded for all planet compositions and radii. We also find that Mars-like topographies are more likely to have seafloor pressures that may form high-pressure ice, reducing seafloor weathering. Thus, for the first time, we show that the composition and topography of the mantle influence the water inventory of rocky planets.

Keywords: Exoplanet catalogs, Exoplanets, Exoplanet astronomy, Exoplanet evolution, Exoplanet structure, Planetary interior
Earth Analogs in Reflected Light: Insights from Early Spectral Characterization in Unconstrained Orbits. A next generation of space-based observatories aims to detect and characterize potentially Earth-like exoplanets around Sun-like stars using reflected-light spectroscopy. However, it remains unclear how such direct-imaging observations, being limited in spectral coverage and signal-to-noise ratio (S/N), translate into constraints on atmospheric composition and habitability. Coronagraphs used for high-contrast imaging typically operate over narrow bandpasses, and exposure time limits can restrict data quality. To optimize observing strategies and instrument design, we use our atmospheric retrieval tool, rfast, to assess the performance of a Habitable Worlds Observatory─type mission across different spectral bandpasses—red, blue, visible, near-infrared (NIR), and their combination—and S/N levels—10, 15, and 20; from moderate to moderate-high observation quality—in retrieving a wide range of 17 atmospheric, surface, bulk, and orbital parameters of a habitable Earth analog. We outline the observation requirements for each parameter and the detection capabilities of each case within a novel scenario where spectral data are taken "early," prior to achieving orbit constraints (which may require repeat visits to a system). For coronagraph-restricted and NIR-only bandpasses, most of the limited retrievable information is already captured at S/N = 10, with little improvement at higher S/Ns. For broader spectral coverage, the quality and quantity of retrieved information improve with increasing S/N, but combining visible and NIR ranges provides the most comprehensive characterization, even at moderate S/Ns. To maximize returns, wider spectral coverage should be prioritized over improving S/N when spectral access is limited.

Keywords: Bayesian statistics, Exoplanets, Astrobiology, Direct imaging, Biosignatures, Habitable planets, Exoplanet atmospheres
Advancing Stellar Parameter Estimation: Uncertainty-Aware Astrophysical Fusion Network for Red Giant Ages and Abundances from Ultra-low-resolution Spectra—Applications to Galactic Archaeology. Red giants are pivotal for tracing the Milky Way's evolutionary history, as their ages and chemical compositions reveal the galaxy's formation and enrichment over cosmic time. Large-scale surveys, such as Gaia and the upcoming China Space Station Telescope, produce millions of ultra-low-resolution spectra (R ≤ 200) and offer broader, more efficient, and cost-effective approaches to studying the Milky Way on a grand scale. However, the loss of fine spectral detail makes age and abundance estimation exceptionally challenging. Traditional methods, reliant on high-resolution data or prederived parameters, underscore the need for innovative approaches to unlock the full potential of such surveys. We present the Uncertainty-Aware Astrophysical Fusion Network (UAFN), a deep learning model tailored to predict stellar ages, [α/Fe], and [C/N] directly from ultra-low-resolution spectra. UAFN harnesses the entire spectral profile, employing a two-stage architecture: a Chem-Net branch for abundance estimation with Bayesian uncertainty quantification and a fusion stage integrating spectral and chemical features for age prediction. On a test set, UAFN achieves a mean absolute error of 0.0171 dex for [α/Fe], 0.0372 dex for [C/N], and 0.1021 dex for log(age). Applied to 156,794 red giant branch stars from LAMOST DR4, UAFN recovers established age─[α/Fe] trends and identifies 7295 anomalous high-α "young" stars, proving its efficacy for Galactic archaeology. By enabling accurate age and abundance measurements from ultra-low-resolution data, UAFN maximizes the scientific yield of current and future surveys, offering a transformative tool for mapping the Milky Way's age structure and chemical evolution across vast stellar populations.

Keywords: Bayesian statistics, Fundamental parameters of stars, Astronomy data analysis, Spectroscopy, Asteroseismology
A Visibility-based 21 cm Bispectrum Estimator for Radio-interferometric Data. We present a fast and scalable estimator for the binned multifrequency angular bispectrum (MABS) and the 3D bispectrum (BS) of the redshifted 21 cm signal from radio interferometric observations. The estimator operates on gridded visibilities and leverages the fast Fourier transform-based acceleration to efficiently compute the MABS and the 3D BS covering all possible triangle configurations. We present the formalism and validate the estimator using simulated visibility data for a known input model BS, considering the Murchison Widefield Array observations with a bandwidth of 30.72 MHz centered at 154.25 MHz. We consider two cases, namely, without flagging, and with flagging, which has exactly the same frequency channels flagged as the actual data. We obtain estimates of the BS for a wide range of triangle shapes covering the scales 0.003 Mpc−1 ≤ k1 ≤ 1.258 Mpc−1. The estimated BS shows excellent agreement with analytical predictions based on the input model BS. We find that the deviations, which are below 20% even in the presence of flagging, are mostly consistent with the expected statistical fluctuations. This work paves the way for reliable observational estimates of the 21 cm BS for the epoch of reionization, where the signal is predicted to be highly non-Gaussian.

Keywords: Diffuse radiation, Visibility function, Observational cosmology, Astronomy data analysis, Non-Gaussianity, Interferometric correlation, Radio interferometry
Detections of Compact Radio Continuum toward Methanol Maser Rings Using the VLA. High-mass protostars are deeply embedded in dust inside their natal cores and are not easily detectable. However, maser emission at centimeter wavelengths, owing to its high brightness, enables us to study gas kinematics in protostars' circumstellar regions. We aim to understand the origin of the ringlike structures outlined by the 6.7 GHz methanol maser emission in six high-mass young stellar objects by performing a sensitive search of the associated radio-continuum emission and derive its properties. We used the Karl G. Jansky Very Large Array in the A configuration at C and K bands in order to image radio-continuum as well as 6.7 GHz methanol and 22 GHz water maser emission. We present the first images of the thermal jets toward four targets in our sample, G23.389+00.185, G23.657−00.127, G28.817+00.365, and G30.400−00.296. In a further target, G23.207$-$00.377, the complex K band continuum emission makes it unclear whether the detected peaks trace jet knots from a single young protostar or mark multiple compact young protostars. The remaining source G31.047+00.356 shows radio continuum emission associated with an evolved H II region.

Keywords: Star forming regions, Stellar jets, Astrophysical masers, Interstellar medium
Examining the Gap in the Chirp Mass Distribution of Binary Black Holes. The mass distribution of binary black holes inferred from gravitational-wave measurements is expected to shed light on their formation mechanisms. An emerging structure in the mass distribution indicates the presence of multiple peaks around chirp masses of 8, 14, and 27 M⊙. In particular, there is a lack of observations between chirp masses of 10 and 12 M⊙. In this paper, we report that observations significantly favour the model that supports suppression of the rate in a narrow chirp mass range over the model that does not include suppression, at a confidence greater than 99.5%. Using another test, which measures the deviation between the inferred chirp mass distributions from the two models, we conservatively estimate a 95% confidence in the presence of a feature. A lack of evidence has been reported in the component mass distribution around the comparable location. The differing conclusions are due to a unique correlation between the primary (heavier of the two masses) and the secondary (lighter of the two masses) masses of binary black holes. This correlation results in increased clustering of measured chirp masses around specific values. However, it remains to be ascertained whether this correlation can be attributed to the weak measurability of features in the component masses.

Keywords: Gravitational wave astronomy, Compact binary stars, Gravitational waves, Gravitational wave sources