Sazuna/UAT_keywords huggingface dataset:
Deep Rest-UV JWST/NIRSpec Spectroscopy of Early Galaxies: The Demographics of C IV and N-emitters in the Reionization Era. JWST has recently discovered a subset of reionization era galaxies with ionized gas that is metal-poor in oxygen and carbon but heavily enriched in nitrogen. This abundance pattern is almost never seen in lower-redshift galaxies but is commonly observed in globular cluster stars. We have recently demonstrated that this peculiar abundance pattern appears in a compact (≃20 pc) metal-poor galaxy undergoing a strong burst of star formation. This galaxy was originally selected based on strong C IV emission, indicating a hard radiation field rarely seen locally. In this paper, we present JWST/NIRSpec observations of another reionization-era galaxy known to power strong C IV emission, the z = 7.04 gravitationally lensed galaxy A1703-zd6. The emission-line spectrum reveals this is a metal-poor galaxy ( ) dominated by a young stellar population (  Myr) that powers a very hard ionizing spectrum (C IV equivalent width, EW = 19.4 Å, He II EW = 2.2 Å). The interstellar medium is highly enriched in nitrogen ( ) with very high electron densities (8–19 × 104 cm‑3) and extreme ionization conditions rarely seen at lower redshift. We also find intense CIV emission (EW ≳ 20 Å) in two new z ≳ 6 metal-poor galaxies. To put these results in context, we search for UV line emission in a sample of 737 z ≳ 4 galaxies with NIRSpec spectra, establishing that 40%(30%) of systems with [O III]+Hβ EW &gt; 2000 Å have N IV] (C IV) detections with EW &gt; 5 Å(&gt; 10 Å). These results suggest high N/O ratios, and hard ionizing sources appear in a brief phase following a burst of star formation in compact high-density stellar complexes.

Keywords: Starburst galaxies, Galaxy chemical evolution, Galactic and extragalactic astronomy, Galaxy abundances, High-redshift galaxies
Geometric Correction for Wind Accretion in Binary Systems. The Bondi–Hoyle–Lyttleton (BHL) accretion model is widely used to describe how a compact object accretes material from a companion's stellar wind in binary systems. However, its standard implementation becomes inaccurate when the wind velocity (vw) is comparable to or less than the orbital velocity (vo), predicting nonphysical accretion efficiencies above unity. This limits its applicability to systems with low wind-to-orbital velocity ratios (w = vw/vo ≤ 1), such as symbiotic systems. We revisit the implementation of the BHL model and introduce a geometric correction factor that accounts for the varying orientation of the accretion cylinder relative to the wind direction. This correction ensures physically plausible accretion efficiencies (η ≤ 1) for all w in circular orbits. Our new implementation naturally predicts the flattening of the accretion efficiency observed in numerical simulations for w &lt; 1, without the need for ad hoc adjustments. We also peer into the implications of our prescription for the less-explored case of eccentric orbits, highlighting the key role of the geometric correction factor in shaping the accretion process. We compare our predictions with numerical simulations, finding good agreement for a wide range of parameters. Applications to the symbiotic star R Aqr and the X-ray binary LS 5039 are presented. This improved implementation offers a more accurate description of wind accretion in binary systems, with implications for stellar evolution, population synthesis, and observational data interpretation.

Keywords: Binary stars, High mass x-ray binary stars, Stellar winds, Stellar accretion, Symbiotic binary stars
Periodic Variability of the Central Stars of Planetary Nebulae Surveyed through the Zwicky Transient Facility. A consensus has been reached in recent years that binarity plays an important role in the formation and evolution of a significant fraction of planetary nebulae (PNe). Utilizing the archived photometric data from the Zwicky Transient Facility survey, we conducted a comprehensive data mining in search of brightness variations in a large sample of Galactic PNe. This effort led to identification of 39 PNe, whose central stars exhibit periodic variation in light curves. Among these objects, 20 are known binary central stars of PNe, while the remaining 19 are new discoveries. Additionally, we identified 14 PNe with central stars displaying anomalous variation in light curves, as well as eight variables based on the high-cadence photometric data. Among the new discoveries of periodicity, we found compelling evidence of binary systems at the centers of two archetypal quadrupolar PNe. We also report on very peculiar brightness variation observed in the central core of the compact PN NGC 6833. Several PNe in our sample deserve follow-up observations, both high-dispersion spectroscopy and high-precision photometry, to reveal the true nature of their central binarity or even multiplicity.

Keywords: Binary stars, Close binary stars, Planetary nebulae nuclei, Planetary nebulae, Stellar evolution
Improving the Temporal Resolution of SOHO/MDI Magnetograms of Solar Active Regions Using a Deep Generative Model. We present a novel deep generative model, named GenMDI, to improve the temporal resolution of line-of-sight (LOS) magnetograms of solar active regions (ARs) collected by the Michelson Doppler Imager (MDI) on board the Solar and Heliospheric Observatory. Unlike previous studies that focus primarily on spatial super-resolution of MDI magnetograms, our approach can perform temporal super-resolution, which generates and inserts synthetic data between observed MDI magnetograms, thus providing finer temporal structure and enhanced details in the LOS data. The GenMDI model employs a conditional diffusion process, which synthesizes images by considering both preceding and subsequent magnetograms, ensuring that the generated images are not only of high quality but also temporally coherent with the surrounding data. Experimental results show that the GenMDI model performs better than the traditional linear interpolation method, especially in ARs with dynamic evolution in magnetic fields.

Keywords: The Sun, Solar active regions, Solar magnetic fields, Solar physics
The Guitar Filament's Magnetic Field Revealed by Starlight Polarization. The Guitar nebula surrounding PSR B2224+65 boasts a pulsar X-ray filament likely aligned with the local magnetic field. We present new RoboPol stellar polarization data distributed along the line of sight to the pulsar. The polarizing effect of intervening magnetized dust allows us to extract a model for the dust-weighted magnetic field. We detect a magnetic field angle consistent with the filament if the pulsar is located in the more distant zone of its parallax-estimated distance range.

Keywords: Interstellar magnetic fields, Starlight polarization, Pulsars
Three Brown Dwarfs Masquerading as High-redshift Galaxies in JWST Observations. We report the spectroscopic identification of three brown dwarf candidates—o005_s41280, o006_s00089, and o006_s35616—discovered in RUBIES using James Webb Space Telescope (JWST) Near-Infrared Spectrograph PRISM/CLEAR spectroscopy. We fit these sources with multiple substellar atmosphere models and present the atmospheric parameters, including effective temperature (Teff), surface gravity, and other derived properties. The results suggest that o005_s41280 and o006_s35616, with Teff in the ranges of 2100–2300 K and 1800–2000 K, respectively, are likely L dwarfs, while o006_s00089, with Teff &lt; 1000 K, is consistent with a late T dwarf classification. The best-fit model spectra provide a reasonable match to the observed spectra. However, distinct residuals exist in the Y, J, and H bands for the two L dwarf candidates, particularly for o006_s35616. Incorporating the extinction parameter into the fitting process can significantly reduce these residuals. The distance estimates indicate that these candidates are about 2 kpc away. The analysis of the color–color diagram using multiple JWST NIRcam photometry suggests that cooler T dwarfs, such as o006_s00089, overlap with little red dots, while hotter L dwarfs, like o005_s41280 and o006_s35616, tend to contaminate the high-redshift galaxy cluster. These findings suggest a brown dwarf contamination rate of approximately 0.1% in extragalactic deep field surveys, with L dwarfs being more frequently detected than cooler T and Y dwarfs.

Keywords: Brown dwarfs, L dwarfs, High-redshift galaxies, Stellar atmospheres, T dwarfs
Study of Hybrid Stars with Nonstrange Quark Matter Cores. In this work, under the hypothesis that quark matter may not be strange, we adopt a modification of the coupling constant of the four-quark scalar interaction   in the two-flavor Nambu–Jona–Lasinio (NJL) model to study nonstrange hybrid stars, where G1 and G2 are two parameters constrained by using the lattice quantum chromodynamics simulation results at the critical temperature and zero chemical potential. The Maxwell construction is used to describe the first-order confinement–deconfinement phase transition in hybrid stars. With recent measurements on neutron star mass, radius, and tidal deformability, the hybrid equations of state are constrained. It is found that pure nonstrange quark matter cores can exist in hybrid stars, possessing 0.026–0.04 M⊙. The maximum hybrid star mass in the framework of the modified NJL model is about 0.1 M⊙ lighter than that in the conventional two-flavor NJL model. It is argued that the binary neutron stars in GW170817 should be hadron stars.

Keywords: Neutron stars, Nuclear astrophysics, Neutron star cores, Compact objects
Precession for the Mode Change in a Gamma-Ray Pulsar. PSR J2021+4026 is a gamma-ray pulsar having variations in its spin-down rate and gamma-ray flux. Its variations in timing and emission are correlated, e.g., a larger spin-down rate for a low gamma-ray flux. We show that the mode change in PSR J2021+4026 can be understood in the precession scenario. In the precession model, the inclination angle is modulated due to precession. At the same time, the wobble angle may decay with time. This results in damping of the precession. Combined with the magnetospheric torque model and the outer gap model, the damped precession can explain that (1) when the inclination angle is larger, the spin-down rate will be larger, accompanied by a lower gamma-ray flux. (2) The variation in amplitude of the gamma-ray flux and spin-down rate is smaller than previous results due to the damping of the precession. The modulation period is becoming shorter due to a smaller wobble angle. In the end, we propose that there are two kinds of modulations in pulsars. Long-term modulations in pulsars may be due to precession. Short-term modulations may be of magnetospheric origin.

Keywords: Neutron stars, Pulsars
Testing Galaxy Formation Models with the Stellar Mass–Halo Mass Relations for Star-forming and Quiescent Galaxies. The tight relationship between the stellar mass and halo mass of galaxies is one of the most fundamental scaling relations in galaxy formation and evolution. It has become a critical constraint for galaxy formation models. Over the past decade, growing evidence has convincingly shown that the stellar mass–halo mass relations (SHMRs) for star-forming and quiescent central galaxies differ significantly: at a given stellar mass, the average host halo mass of quiescent centrals is more massive than that of star-forming centrals. Despite the importance of this feature, its scientific implications have not yet been fully recognized or thoroughly explored in the field. In this work, we demonstrate that the semi-analytical model L-GALAXIES successfully reproduces these observational results, whereas three state-of-the-art hydrodynamic galaxy formation simulations (TNG, Illustris, and EAGLE) do not. Consequently, in L-GALAXIES, star-forming central galaxies are more efficient at converting baryons into stars than quiescent central galaxies at a given halo mass, while the other models predict similar efficiencies for both populations. Further analysis reveals that these fundamental discrepancies stem from distinct evolutionary paths on the stellar mass–halo mass plane. We show that the observed SHMRs for star-forming and quiescent galaxies support galaxy formation models in which quenching only weakly correlates with halo assembly histories and the stellar mass of star-forming galaxies can increase significantly after cosmic noon. In contrast, models in which quenching strongly preferentially happens in early-formed halos are not very favored. Additionally, we find that galaxy downsizing is present in L-GALAXIES and TNG but absent in Illustris and EAGLE.

Keywords: Galaxy dark matter halos, Galaxy formation, Galaxy evolution, Galaxy groups
Simultaneous NICER and NuSTAR Observations of the Neutron Star Low-mass X-Ray Binary Serpens X-1. We present the first contemporaneous NICER and NuSTAR analysis of the low-mass X-ray binary Serpens X-1 obtained in 2023 June, performing broadband X-ray spectral analysis modeling of the reprocessed emission with RELXILLNS from 0.4 to 30 keV. We test various continuum and background estimation models to ensure that our results do not hinge on the choice of model used, and found that the detection of reflection features is independent of the choice of both continuum and background model. The position of the inner accretion disk is consistent with the last stable circular orbit (Rin ≤ 1.2 RISCO) and a low inclination of i ≤ 8.3°. Additionally, we investigate the presence of the low-energy (∼1 keV) Fe L complex in the data from NICER and the Reflection Grating Spectrometer on XMM-Newton that was previously reported in the literature. We find that the line is at most a 2% feature relative to the reprocessed continuum, and are unable to claim a definitive detection for the current data set. However, we discuss plausible conditions and systems that would increase the likelihood of detecting this feature in the future.

Keywords: Accretion, Neutron stars, Low-mass x-ray binary stars
Comparing Methods for Calculating Solar Energetic Particle Intensities: Rebinning versus Spectral Binning. Solar energetic particle (SEP) events have been observed for decades in the interplanetary medium by spacecraft measuring the intensity of energetic ions and electrons. These intensities provide valuable information about particle acceleration, the effects of bulk plasma dynamics on particle transport, and the anisotropy of particle distributions. Since measured intensities are typically reported in narrow energy bins, it is common to rebin intensities over a wider energy range to improve counting statistics. We investigate two methods for calculating intensities across multiple energy bins: (a) rebinned intensity ( ), which is calculated by integrating the intensity over energy space and corresponds to the intensity at an effective energy that depends on the time-varying spectral index, and (b) spectral binned intensity ( ), calculated by integrating the log intensity in log–energy space, yielding the intensity at the log-centered energy that is independent of the spectral index and remains constant over time. We compare these methods using Parker Solar Probe (PSP) IS⊙IS measurements of energetic protons, and we prescribe criteria for selecting the appropriate method for different scenarios. Our results show that the rebinned intensity is consistently larger (up to a factor of 5) than the spectral binned intensity for two SEP events observed by PSP, although the time series of the two methods are strongly correlated. Overall, both measures are important for SEP spectral analysis, and the selection of the appropriate measure depends on whether a physical (spectral binned intensity) or a statistical (rebinned intensity) representation is needed for a given analysis.

Keywords: Solar energetic particles, Solar physics, Solar wind
Influence of Modeling Assumptions on the Inferred Dynamical State of Resonant Systems: A Case Study of the HD 45364 System. Planetary systems exhibiting mean motion resonances (MMRs) offer unique opportunities to study the imprint of disk-induced migration on the orbital architectures of planetary systems. The HD 45364 system, discovered via the radial velocity (RV) method to host two giant planets in a 3:2 MMR, has been the subject of several studies attempting to reconstruct the system's orbital migration history based on its present-day resonant configuration. Recently, Z. Li et al. called into question the system's residence in the 3:2 MMR based on a revised orbital solution derived from an expanded set of RV observations that extend the time baseline of the original discovery data by over a decade. However, we show that inferences about the planets' dynamical state with respect to the 3:2 MMR are sensitive to the particular prior assumptions adopted in the orbital modeling. Using N-body dynamical models, we show that orbital solutions constrained to reside deep in the 3:2 MMR fit the RV data with a similar quality to unconstrained orbital solutions. We conclude that the RV observations of HD 45364 are consistent with orbital configurations produced by smooth migration and resonance capture. We further show that past convergent orbital migration can reproduce the system's present-day orbital configuration provided that the ratio of migration to eccentricity damping timescales, K, was in the range 11 ≲ K ≲ 144. We also find that dynamical interactions in the system can break the usual mass–inclination degeneracy inherent to Keplerian models of RV observations and constrain the planets' absolute masses to within a factor of ∼1.5.

Keywords: Exoplanet dynamics, Exoplanets, Orbital resonances, Celestial mechanics, Radial velocity
Estimating the Black Hole Spin for the X-Ray Binary MAXI J1727-203 Based on Insight-HXMT. We constrain the spin of the black hole candidate MAXI J1727-203 using Insight-HXMT data. Due to limited Insight-HXMT observations covering only part of the outburst, NICER data were used to analyze the full outburst's state transitions; we identified two of three HXMT observations in the high soft state and applied the continuum-fitting method to measure the spin. Based on previous estimates and continuum spectral fittings, we explored the parameter space and found that the best-fitting values were (D, i, M) ≈ (6 kpc, 30°, 12 M⊙). We also tested the variation of these parameters using Monte Carlo simulations, sampling over 3000 sets within the parameter ranges 5.9 kpc &lt; D &lt; 7 kpc, 24° &lt; i &lt; 35°, and 10 M⊙ &lt; M &lt; 14 M⊙, yielding a spin measurement of   (1σ). In addition, we analyzed NuSTAR data in the low hard state and found a good fit with the tbabs∗(diskbb+powerlaw) model, with no significant iron line features observed in the residuals; therefore, the previous reflection model results suggesting an extremely high spin overestimates the black hole spin.

Keywords: Black hole physics, X-ray binary stars, High energy astrophysics, Kerr black holes, Stellar accretion disks
Primordial Black Holes in the Solar System. If primordial black holes (PBHs) of asteroidal mass make up the entire dark matter, they could be detectable through their gravitational influence in the solar system. In this work, we study the perturbations that PBHs induce on the orbits of planets. Detailed numerical simulations of the solar system, embedded in a halo of PBHs, are performed. We find that the gravitational effect of the PBHs is dominated by the closest encounter. Using the Earth–Mars distance as an observational probe, we show that the perturbations are smaller than the current measurement uncertainties and thus PBHs are not directly constrained by solar system ephemerides. We estimate that an improvement in the ranging accuracy by an order of magnitude or the extraction of signals well below the noise level is required to detect the gravitational influence of PBHs in the solar system in the foreseeable future.

Keywords: Milky Way dark matter halo, Black holes, Gravitation, Solar system, Orbital anomalies, Solar system evolution, Close encounters, Dark matter, Primordial black holes
Radio Polarization from Runaway Star Bowshocks. I. The General Case. High velocity stars move through the interstellar medium with V &gt; 30 km s‑1. When the star has powerful winds, under the appropriate conditions, the interaction of the wind with the interstellar material produces a system of shocks. The outer shock, called the bowshock, perturbs the ambient medium, heating and compressing the gas. The dust in the compressed bowshock cools, producing infrared radiation. This emission appears as extended coma-shape structures. The discovery of radio nonthermal emission from two stellar bowshock nebulae indicates that these sources might be accelerating electrons up to relativistic energies. The produced nonthermal radio emission is most probably synchrotron, which has a high degree of polarization. In this work we model the synchrotron emission of runaway massive star bowshocks aiming to produce synthetic radio emission and polarization maps for two frequencies: 1.40 and 4.86 GHz. We model the interacting plasmas in a steady-state regime by means of magnetohydrodynamics simulations and we compute the injection and transport of the relativistic electrons in the diffusion approximation. We include in the model the most important depolarization effects. Our main conclusions are (i) the effects of Faraday rotation within the source are important at the lowest frequency considered, (ii) inferring the local magnetic field direction from polarization measurements only can be misleading, (iii) thermal radio emission produced by ionized plasma within the bowshock structure and surroundings can surpass the polarized one for the considered frequencies, and (iv) the contribution from the background electrons is minor.

Keywords: Radio continuum emission, Stellar winds, Non-thermal radiation sources
Understanding Streaming Instabilities in the Limit of High Cosmic-Ray Current Density. A critical component of particle acceleration in astrophysical shocks is the nonresonant (Bell) instability, where the streaming of cosmic rays (CRs) leads to the amplification of magnetic fields necessary to scatter particles. In this work we use kinetic particle-in-cell simulations to investigate the high-CR-current regime, where the typical assumptions underlying the Bell instability break down. Despite being more strongly driven, significantly less magnetic field amplification is observed than in low-current cases, an effect due to the anisotropic heating that occurs in this regime. We also find that electron-scale modes, despite being the fastest growing, mostly lead to moderate electron heating and do not affect the late evolution or saturation of the instability.

Keywords: Plasma physics, Plasma astrophysics, Shocks, Magnetic fields, Cosmic rays