Sazuna/UAT_keywords huggingface dataset:
Recovering Ion Distribution Functions. I. Slepian Reconstruction of Velocity Distribution Functions from MMS and Solar Orbiter. Plasma velocity distribution functions (VDFs) constitute a fundamental observation of numerous operational and future missions. An efficient parameterization of VDFs is crucial for (1) preserving enough information to investigate macroscopic moments along with kinetic effects, (2) producing smooth distributions whereby it is possible to perform derivatives in phase space to support numerical solvers, and (3) economic data management and its storage. Previous studies have used spherical harmonics as an efficient basis for representing electron VDFs. In this paper, we present a novel algorithm targeted toward decomposing ion VDFs measured by electrostatic analyzers on board Magnetospheric Multiscale (MMS) Mission and Solar Orbiter (SolO) spacecraft. We use Slepian functions, custom-designed bases providing compact support in phase space, initially developed in information theory and later used for terrestrial and planetary applications. In this paper, we choose well-studied, well-measured, and complex intervals from MMS and SolO containing a range of simpler gyrotropic and agyrotropic distributions to benchmark the robustness of our reconstruction method. We demonstrate the advantages of using Slepian functions over spherical harmonics for solar wind plasma distributions. We also demonstrate that our choice of basis representation efficiently preserves phase space complexities of a 3D agyrotropic distribution function. This algorithm shown in this study will be extended to Parker Solar Probe and future missions such as Helioswarm.

Keywords: Space plasmas, Solar wind, Regression, Solar instruments
Linking Analytic Light-curve Models to Physical Properties of Kilonovae. In binary neutron star mergers, lanthanide-rich dynamical ejecta and lanthanide-poor postmerger ejecta have often been linked to red and blue kilonova emission, respectively. However, analytic light-curve modeling of kilonovae often results in ejecta parameters that are at odds with such expectations. To investigate the physical meaning of the derived parameters, we perform analytic modeling of the kilonova light curves calculated with realistic multidimensional radiative transfer based on numerical relativity simulations. Our fiducial simulations adopt a faster-moving, less massive dynamical ejecta and slower-moving, more massive postmerger ejecta. The results of analytic modeling, however, show that the inferred "red" component is more massive and slower, while the "blue" component is less massive and faster, as also inferred for GW170817/AT 2017gfo. This suggests that the parameters derived from light-curve modeling with an analytic model do not represent the true configuration of the kilonova ejecta. We demonstrate that the postmerger ejecta contributes to both blue and red emissions: the emission from the postmerger ejecta is absorbed and reprocessed to red emission by the dynamical ejecta with a higher lanthanide fraction. Our results caution against separately discussing the origins of the red and blue components derived from the analytic models. Despite the challenges in the parameter estimation, we show that the estimate of the total ejecta mass is rather robust within a factor of a few, reflecting the total luminosity output. To derive the reliable total ejecta mass, multiepoch observations in near-infrared wavelengths near their light-curve peaks are important.

Keywords: Neutron stars, Transient sources, Time domain astronomy, Gravitational waves, Radiative transfer simulations
Short-term Balmer Line Emission Variability in M Dwarfs. M dwarfs make up the majority of stars, offering an avenue for discovering exoplanets due to their smaller sizes. However, their magnetic activity poses challenges for exoplanet detection, characterization, and planetary habitability. Understanding their magnetic activity, including surface starspots and internal dynamos, is crucial for exoplanet research. In this study, we present short-term variability in four Balmer emission lines, Hα, Hβ, Hγ, and Hδ, for a sample of 77 M dwarfs of varying spectral types and binarity. Stars were observed using the MDM Observatory's Ohio State Multi-Object Spectrograph on the 2.4 m telescope and the Modular Spectrograph on the 1.3 m telescope. These data are combined with TESS photometry to explore the connection between spectroscopic and photometric variability. We observe sporadic short-term variability in Balmer lines for some stars, on a timescale ≳15 min, but much shorter than the stellar rotation period. We calculate periods for stars lacking those measurements, reevaluate the amplitude (Rvar)–activity relation for the Hα line from A. Garcìa Soto et al., and extend our analysis to the Hβ, Hγ, and Hδ lines, which indicates that the relation becomes increasingly dispersed for higher-order Balmer lines. This is consistent with increased intrinsic variability from lower- to higher-order lines. Additionally, we compute the Balmer decrement, using Hβ as the fiducial, for stars where we could measure Hγ and/or Hδ. The Balmer decrement can show distinct patterns during white-light flares, with significant differences even for the same star. We also find evidence for dark spots on TIC 283866910.

Keywords: M dwarf stars, Stellar rotation, Stellar flares, Stellar activity
The Direct Measurement of Gravitational Potential Decay Rate at Cosmological Scales. II. Improved Dark Energy Constraint from z ≤ 1.4. The gravitational potential decay rate (DR) is caused by the cosmic acceleration of the Universe, providing a direct probe into the existence of dark energy (DE). We present measurements of DR and explore its implications for DE models using the DR9 galaxy catalog of the Dark Energy Spectroscopic Instrument (DESI) imaging surveys and the Planck cosmic microwave background maps. Our analysis includes six redshift bins within the range of 0.2 ≤ z &lt; 1.4 and achieves a total significance of 3.1σ, extending the DR measurements to a much higher redshift compared to Dong et al., which focused on 0.2 ≤ z &lt; 0.8. Other improvements involve addressing potential systematics in the DR-related measurements of correlation functions, including imaging systematics and magnification bias. We explore the constraining power of DR on both the wCDM model and the w0waCDM model. We find that the addition of DR can significantly improve the DE constraints, over Sloan Digital Sky Survey baryon acoustic oscillation (BAO) data alone or the PantheonPlus supernovae (SNe) compilation alone, although it shows only a modest improvement for DESI BAO. In the wCDM model, all three probes—DR, DESI BAO, and SNe—favor w = ‑1. For the w0waCDM, while DESI BAO prefers w0 &gt; ‑1 and wa &lt; 0, the SNe Ia and DR data constrain   and  . Namely, SNe Ia and DR data have no preference on dynamical DE over Λ.

Keywords: Cosmology, Cosmic microwave background radiation, Gravitational lensing, Large-scale structure of the universe
Carving Out the Inner Edge of the Period Ratio Distribution through Giant Impacts. The distribution of orbital period ratios between adjacent observed exoplanets is approximately uniform, but exhibits a strong falloff toward close orbital separations. We show that this falloff can be explained through past dynamical instabilities carving out the period ratio distribution. Our suite of numerical experiments would have required ∼3 million CPU hr through direct N-body integrations, but was achieved with only ≍50 CPU hr by removing unstable configurations using the Stability of Planetary Orbital Configurations Klassifier machine learning model. This highlights the role of dynamical instabilities in shaping the observed exoplanet population, and shows that the inner part of the period ratio distribution provides a valuable observational anchor on the giant impact phase of planet formation.

Keywords: Exoplanet astronomy, Celestial mechanics, Exoplanet dynamics
Plasma Instability Evolution and Particle Heating in the Foot Region of Perpendicular Shocks in Young Supernova Remnants. Particle acceleration from collisionless shocks is a key mechanism in the generation of cosmic rays. In particular, shocks in young supernova remnants (SNRs) are considered to be a major source of galactic cosmic rays. This study investigates the early-stage plasma instability evolution and subsequent electron and ion heating in the foot region of high-Mach-number perpendicular shocks in young SNRs, using 2D particle-in-cell simulations. Unlike previous simulations that cover larger regions of the shock structure—including the downstream, shock, and upstream regions—our simulations are local, limited to the shock transition region, and focus on practical parameters with a nonrelativistic shock velocity (v ≈ 0.02c) and the standard mass ratio between protons and electrons. We examined scenarios with and without the presence of return protons, and our results reveal that the Buneman instability, followed by the ion two-stream instability, dominates the early electron-heating process. We observed long-lasting ion heating in the case without return protons and note that the Weibel instability did not emerge within the simulation time frame. These findings enhance the understanding of plasma behavior in young SNR shocks and suggest that local simulations with practical parameters are crucial for exploring electron-heating mechanisms, while also highlighting the conditions under which the Weibel instability may or may not emerge.

Keywords: Supernova remnants, Shocks, Plasma astrophysics
No Glitch in the Matrix: Robust Reconstruction of Gravitational Wave Signals under Noise Artifacts. Gravitational wave (GW) observations by ground-based detectors such as LIGO and Virgo have transformed astrophysics, enabling the study of compact binary systems and their mergers. However, transient noise artifacts, or "glitches," pose a significant challenge, often obscuring or mimicking signals and complicating their analysis. In this work, we extend the Attention-boosted Waveform Reconstruction network (AWaRe) to address glitch mitigation, demonstrating its robustness in reconstructing waveforms in the presence of real glitches from LIGO's third observing run. Without requiring explicit training on glitches, AWaRe accurately isolates GW signals from data contaminated by glitches spanning a wide range of amplitudes and morphologies. We evaluate this capability by investigating the events GW191109 and GW200129, which exhibit strong evidence of antialigned spins and spin precession, respectively, but may be adversely affected by data quality issues. We find that, regardless of the potential presence of glitches in the data, AWaRe reconstructs both waveforms with high accuracy. Additionally, we perform a systematic study of AWaRe's performance on a simulated catalog of injected waveforms in real LIGO glitches and obtain reliable reconstructions of the waveforms. By subtracting the AWaRe reconstructions from the data, we show that the resulting residuals closely align with the background noise that the waveforms were injected in. The robustness of AWaRe in mitigating glitches, despite being trained exclusively on GW signals and not explicitly on glitches, highlights its potential as a powerful tool for improving the reliability of searches and characterizing noise artifacts.

Keywords: Gravitational waves
Forecasting of the Time-dependent Fluxes of Antiprotons in the AMS-02 Era. The spectra of Galactic cosmic rays (GCRs) contain crucial information about their origin and propagation through the interstellar medium. When GCRs reach Earth, they are significantly influenced by the solar wind and the heliospheric magnetic field, a phenomenon known as solar modulation. This effect introduces time-dependent variations in GCR fluxes. The AMS-02 experiment has released time-dependent flux data for protons, electrons, and positrons, revealing clear correlations with solar modulation. Studies suggest that cosmic rays with the same charge, such as protons and helium nuclei, exhibit similar or the same solar modulation parameters. In this work, we derive the local interstellar spectrum (LIS) for protons and positrons under the assumption of a common solar modulation potential, using data from Voyager 1 and a 7 yr average from AMS-02. Similarly, the LIS for antiprotons and electrons is derived by assuming they are governed by a separate solar modulation potential. We demonstrate that the time-dependent fluxes of positrons and protons can be accurately modeled using the same set of solar modulation parameters within a modified force-field approximation framework. Based on this, we predict the time-dependent fluxes of antiprotons using the corresponding electron flux data.

Keywords: Galactic cosmic rays, Heliosphere
High-frequency Coronal Alfvénic Waves Observed with DKIST/Cryo-NIRSP. The presence and nature of low-frequency (0.1–10 mHz) Alfvénic waves in the corona have been established over the past decade, with many of these results coming from coronagraphic observations of the infrared Fe XIII line. The Cryo-NIRSP instrument situated at DKIST has recently begun acquiring science-quality data of the same Fe XIII line, with at least a factor of 9 improvement in spatial resolution, a factor of 30 increase in temporal resolution, and an increase in signal-to-noise ratio, when compared to the majority of previously available data. Here we present an analysis of 1 s cadence sit-and-stare data from Cryo-NIRSP, examining the Doppler velocity fluctuations associated with the Fe XIII 1074 nm coronal line. We are able to confirm previous results of Alfvénic waves in the corona and explore a new frequency regime. The data reveal that the power-law behavior of the Doppler velocity power spectrum extends to higher frequencies. This result appears to challenge some models of photospheric-driven Alfvénic waves that predict a lack of high-frequency wave power in the corona owing to strong chromospheric damping. Moreover, the high-frequency waves do not transport as much energy as their low-frequency counterparts, with less time-averaged energy per frequency interval. We are also able to confirm the incompressible nature of the fluctuations with little coherence between the line amplitude and Doppler velocity time series.

Keywords: Magnetohydrodynamics, Infrared spectroscopy, Solar coronal waves, Solar corona, Alfven waves
The Discovery of Rapid Polarization Angle Variation during the 2022 Outburst of XTE J1701-462. The geometry of the Comptonization corona in neutron star low-mass X-ray binaries is still unclear. We conducted time-resolved polarimetric analysis of the archival observations of XTE J1701–462 obtained with the Imaging X-ray Polarimeter Explorer during its 2022 outburst and found that the polarization angle (PA) varied significantly with time when the source was in the normal branch, with 67∘ ± 8∘ in the first epoch, ‑34∘ ± 8∘ in the second, and ‑58∘ ± 8∘ in the third, last epoch. Meanwhile, the polarization degree remained constant at around 2%, above the minimum detectable polarization at the 99% confidence level (MDP99). The rapid PA variation causes depolarization in the time-averaged data, resulting in a nondetection as reported in the literature. The rapid (intraday) PA variation may suggest that there is a fast transformation of the corona geometry, likely switching from a slab geometry with enhanced disk emission and reflection, to a more vertically extended spreading layer geometry.

Keywords: Accretion, X-ray transient sources, Polarimetry
Rising from the Ashes: A Metallicity-dependent Star Formation Gap Splits the Milky Way's α Sequences. The elemental abundance distribution of stars encodes the history of the gas-phase abundance in the Milky Way. Without a large, unbiased sample of highly precise stellar ages, the exact timing and nature of this history must be inferred from the abundances. In the two-dimensional plane of [α/Fe]–[Fe/H], it is now clear that two separate populations exist—the low-α and high-α sequences. We propose that a brief (∼300 Myr) halt in star formation within a narrow metallicity bin can lead to a bimodal [α/Fe] distribution at that metallicity, assuming a rapidly declining gas phase [α/Fe]. Using simulations of an idealized setup of a high-z galaxy merger, we show that the merger with the Gaia-Sausage-Enceladus satellite at z ∼ 2 is one possible way to trigger such a gap in the Milky Way. This mechanism may also operate in nonmerger scenarios. We predict a ∼300 Myr gap in stellar ages at a fixed [Fe/H] where the α bimodality is prominent ([Fe/H] ≲ ‑0.2).

Keywords: Hydrodynamical simulations, Galaxies, Starburst galaxies, Milky Way formation, Milky Way Galaxy physics, Milky Way disk, Post-starburst galaxies
Single-pulse Morphology of PSR J1935+1616 (B1933+16) Based on Archival Data from FAST. We utilized archive data from the Five-hundred-meter Aperture Spherical Radio Telescope (FAST) to analyze the single-pulse profile morphology of PSR J1935+1616 (B1933+16). The results show that PSR J1935+1616 exhibits significant micropulses as well as various changes in single-pulse profile morphology. In the FAST archive data, a total of 969 single pulses with microstructure were identified, accounting for 9.69% of the total pulse sample, with characteristic widths of  μs. About half of these pulses display quasiperiodic micropulses, with a periodicity of 231.77 ± 9.90 μs. Among the 520 single pulses with quasiperiodic microstructure, 208 also exhibit quasiperiodicity in circular polarization, with a characteristic period of  . The micropulse characteristic width in circular polarization is 106.52 ± 46.14 μs. Compared to normal pulses, the relative energy (E/&lt;E&gt;) of a single pulse with microstructure follows a double-Gaussian distribution, while those of normal pulses follow a single-Gaussian distribution. Based on the intensity of the leading and trailing components in the single-pulse profile morphology of PSR J1935+1616, we classified the pulses into four morphological modes (A, B, C, and D). The relative energy distribution of pulses in Mode A is significantly different from the others, following a double-Gaussian distribution, while the relative energy distributions in Modes B, C, and D follow a single-Gaussian distribution. Our study also suggests a possible correlation between micropulses and single-pulse profile morphology. Single pulses with micropulses are most likely to occur in Mode A, while their occurrence is least likely in Mode D.

Keywords: Radio pulsars, Pulsars
SDSS-IV MaNGA: Spectroscopic Probes of Neutral Gas in Nearby Galaxies. Cool, dusty interstellar material plays an important role in the chemical evolution of galaxies. We present an analysis of this material across galaxy type through a spatially resolved spectral stacking analysis of galaxies from the MaNGA survey. With stellar population synthesis, we isolate neutral gas signals from resonance lines, comparing outcomes across model types, galactic geometry, and host stellar mass and age. We find that both synthetic and empirical models fail to capture the range of galactic chemical abundances. There is also notable Na I contamination from the Galaxy's interstellar medium (ISM) in the MILES empirical stellar library. We are unable to reliably determine the column density of the gas due to the accuracy of absorption measurements, but differential analysis across radius and inclination reveals consistent and significant path-length dependent absorption in the equivalent width of Na I. We note similar but lesser trends in a narrow Ca II index. We find no trends in Ca I or in a broad Ca II index, indicating its ISM insensitivity and providing evidence in favor of its utility in determining the age and chemical content of stellar populations. Our data shows there is a cool ISM component in most external galaxies with Dn(4000) &lt; 1.7 that can be traced by Na I. Lastly, we caution that the characterization of gas kinematics traced by Na I in such low-resolution spectra is subject to systematic effects due to the chosen approach to stellar population modeling.

Keywords: Galactic winds, Late-type galaxies, Galaxy evolution, Interstellar medium, Early-type galaxies
Spatial and Chemical Complexity in the W75N Star-forming Region. We present the analysis of NOEMA interferometric observations of the high-mass star-forming region W75N(B) with a focus on molecular composition and distribution of prebiotic molecules in the source's multiple cores. Over 20 molecules are identified across the region, with many being fit for column density, rotational temperature, spectral line FWHM, and vlsr. This work includes the first known detection and initial analysis of complex organic molecules in the MM2 and MM3 regions. Furthermore, parameter maps were created from the six molecules that were well fit across multiple regions. The molecular emission was imaged and correlated across different molecules and the continuum to reveal structural features. From the spatial and spectral analysis of the MM1 region, these results concur with those from other studies showing that there is a difference in chemical composition between the MM1a and MM1b regions, with sulfur-bearing molecules tracing MM1a and organic molecules tracing MM1b. The molecular emission imaged toward the MM3 region reveals two peaks, possibly indicating the presence of multiple young stellar objects. These results provide detailed quantitative information about the physical parameters and distributions of molecules in this source. Additionally, these results are part of a follow-up of a single-dish survey of multiple star-forming regions and are discussed in this context.

Keywords: Star forming regions, Molecular spectroscopy, Astrochemistry, Radio interferometry, Pre-biotic astrochemistry
An Agnostic Approach to Building Empirical Type Ia Supernova Light Curves: Evidence for Intrinsic Chromatic Flux Variation Using Nearby Supernova Factory Data. We present a new empirical Type Ia supernova (SN Ia) model with three chromatic flux variation templates: one phase dependent and two phase independent. No underlying dust extinction model or patterns of intrinsic variability are assumed. Implemented with Stan and trained using spectrally binned Nearby Supernova Factory spectrophotometry, we examine this model's 2D, phase-independent flux variation space using two motivated basis representations. In both, the first phase-independent template captures variation that appears dust-like, while the second captures a combination of effectively intrinsic variability and second-order dust-like effects. We find that ≈13% of the modeled phase-independent flux variance is not dust-like. Previous empirical SN Ia models either assume an effective dust extinction recipe in their architecture, or only allow for a single mode of phase-independent variation. The presented results demonstrate such an approach may be insufficient, because it could "leak" noticeable intrinsic variation into phase-independent templates.

Keywords: Observational cosmology, Type Ia supernovae