Sazuna/UAT_keywords huggingface dataset:
First-principles Polar-cap Currents in Multipolar Pulsar Magnetospheres. X-ray pulse-profile modeling of millisecond pulsars offers a direct route to measuring neutron star masses and radii, thereby constraining the dense-matter equation of state. However, standard analyses typically rely on ad hoc hotspot parameterizations rather than self-consistent physical models. While connecting surface heating directly to the magnetospheric geometry provides a more natural physical pathway, computing global magnetospheric solutions is too computationally expensive to perform on-the-fly during parameter inference. In this work, we bridge this gap by deriving fully analytic, first-principles expressions for surface return currents in mixed dipole─quadrupole magnetospheres. Working within force-free electrodynamics, we generalize the field-aligned current invariant Λ, the crucial scalar that maps the far-zone magnetic structure to the near-zone heating rate, from the standard dipole approximation to arbitrary quadrupolar configurations. We demonstrate that even when the quadrupole component is subdominant in the far zone (the mixing regime), using a dipole-based heating prescription fails to capture the significant enhancement or suppression of the return-current density on the polar cap. Our consistent quadrupole-aware framework reveals that these multipolar currents redistribute the surface heating, leading to systematic discrepancies in predicted pulse profiles that are amplified by atmosphere beaming and can reach ∼30% near pulse peaks. These results provide a rigorous analytic foundation for mapping global magnetic geometry to surface heating in multipolar magnetospheres, enabling physically consistent inference beyond the idealized dipole approximation.

Keywords: Neutron stars, X-ray astronomy, Pulsars
XRISM Observation of the Supernova Remnant N103B: Velocity Structure and Thermal Properties. We present the first analysis of the X-ray Imaging and Spectroscopy Mission (XRISM) observation of the supernova remnant (SNR) N103B. We fit the X-ray spectrum taken with the Resolve microcalorimeter, which captured emission lines from the predominantly ejecta elements Si, S, Ar, Ca, Cr, Mn, and Fe. Notably, our fits require a previously unidentified high-temperature, highly ionized, Fe-dominated plasma component with particularly high Cr and Mn abundances, matching a feature also present in the recent XRISM analysis of the SNR N132D. We find that all ejecta in N103B exhibits significant line broadening arising mostly from thermal Doppler broadening: increasing from σth ∼ 1700 km s−1 for intermediate-mass element (IME: Si, S, Ar, and Ca) ejecta to ∼2800 km s−1 for Fe-rich ejecta. These velocities correspond to reverse shock velocities of ∼3500 and ∼5900 km s−1, respectively, in the ejecta frame of rest. Finally, we find that the IMEs are redshifted with a bulk velocity of ∼360 km s−1 while the Fe-dominated components are split: one redshifted at ∼1560 km s−1 and the other blueshifted at ∼1020 km s−1. Our results provide further support for the double-ring structure of N103B as it expands into the bipolar winds of a nondegenerate companion and highlight the strength of high-resolution spectroscopic observations of SNRs.

Keywords: Supernova remnants, High resolution spectroscopy, X-ray astronomy, High energy astrophysics
Comparative Analysis of Properties of Coronal Mass Ejections at High and Low Apparent Latitudes in 1996─2025. This study examines the statistical properties of coronal mass ejections (CMEs) over two and a half solar cycles (1996─2025) using coronal observations from the SOHO LASCO CDAW and CACTus catalogs, supplemented by sunspot number records and in situ measurements of interplanetary CMEs (ICMEs) from the Ulysses spacecraft. Focusing on differences between CMEs originating at different apparent latitudes (AL), we analyzed CME annual rates, spatial distributions, and kinematic properties. The total yearly number of CMEs follows the solar cycle, with high-AL CMEs showing a stronger link than low-AL ones. A pronounced solar-cycle-dependent variation is observed between the number of CMEs detected in the corona and the ICMEs in the solar wind. During solar maximum, ICME counts are substantially lower than coronal ejection rates, likely due to enhanced deflection and interaction in the complex interplanetary medium, whereas during solar minimum, Ulysses captured several times more high-latitude ICMEs. ICME occurrence at Ulysses follows the solar cycle with a systematic two-year phase lag. Spatially, high-AL CMEs display a south─north asymmetry, being preferentially directed northward across all phases of the solar cycle except the solar maximum. Low-AL CMEs show a slight southward bias at solar maximum. During the rising phase, they are northward on the western side and southward on the eastern side, with the opposite pattern in the declining phase. The linear speed and angular width of both low- and high-AL CMEs track the solar cycle, with the CME angular width variations preceding sunspot activity, which suggests potential prognostic applications.

Keywords: Solar coronal mass ejections, Heliosphere
Testing Magnetic Field Configurations in Spider Pulsar PSR J1723−2837 with IXPE. We present the first X-ray polarimetry observations of a redback millisecond pulsar binary, PSR J1723−2837, with the Imaging X-ray Polarimetry Explorer (IXPE). We conduct a spectropolarimetric analysis combining IXPE data with archival Chandra, XMM-Newton, NuSTAR, and Swift observations. We explore two limiting magnetic field configurations, parallel and perpendicular to the bulk flow, and simulate their expected polarization signatures using the 3DPol radiative transport code. To account for the rapid rotation of the polarization angle (PA) predicted by these models, we implement a phase-dependent Stokes alignment procedure that preserves the polarization degree (PD) while correcting for a phase-rotating PA. We also devise a new maximum likelihood fitting strategy to determine the phase-dependence of the PA by minimizing the PD uncertainty. This technique hints that the binary may be rotating clockwise relative to the celestial north pole. We find no significant detection of polarization in the IXPE data, with PD ≲50% at the 99% confidence level. Our results exclude the high-PD scenario predicted by the perpendicular field model during the brightest orbital phase bin. Simulations show that doubling the current exposure would make the parallel configuration detectable. The new PA rotation technique is also applicable to IXPE data of many sources whose intrinsic PA variation is a priori not known but is strictly periodic.

Keywords: Neutron stars, Binary pulsars
Proton Trapping in Ganymede's Magnetosphere: A Quantitative Test Particle Study. Ganymede, the largest moon in the solar system, possesses an intrinsic dipole magnetic field, creating a mini-magnetosphere within Jupiter's giant magnetosphere. Energetic protons from the upstream Jovian plasma can become temporarily confined within this small system, giving rise to a partial ring current whose asymmetric configuration has been suggested by previous models. However, the specific conditions that allow proton trapping and the physical origin of the partial ring current remain unclear. In this study, we perform test particle simulations based on three-dimensional magnetohydrodynamics electromagnetic fields corresponding to the Galileo G8 flyby to quantitatively investigate proton trapping in Ganymede's magnetosphere. Our results indicate that less than 1% of protons injected from the magnetotail remain trapped within the closed field line region, whereas most precipitate to the surface or escape from the magnetosphere, leading to a partial ring current structure. In addition, the trapping region is restricted to a narrow phase-space domain that corresponds to kinetic energies below ∼75 keV, pitch angles between 60° and 120°, and gyrophases near 45°. These findings demonstrate the fundamental constraint from the small size of Ganymede's magnetosphere on proton trapping, a feature that can be further verified by future in situ observations.

Keywords: Planetary magnetospheres, Ganymede
The 2024 July 23 Event: A Case Study of a Multispacecraft, Fe-rich Solar Energetic Particle Event. Occasionally, solar energetic particle (SEP) events associated with fast, wide coronal mass ejections (CMEs) driving interplanetary shocks exhibit Fe/O abundance ratios that are significantly higher than the nominal value of 0.134. The cause of this enrichment in Fe remains unclear, but there are two prevailing theories: contribution from flare-accelerated material, and reacceleration of suprathermal remnant flare material by a quasiperpendicular shock. The 2024 July 23 SEP event was observed by four spacecraft spread over ∼160° of solar longitude and 0.4 au in radial distance. We examine the H, He, O, and Fe spectra and He/H and Fe/O abundance ratios observed at each spacecraft, and find that three measured Fe/O ratios &gt;0.6 were relatively independent of energy. The fourth spacecraft measured strongly energy-dependent Fe/O ratios reaching very low values of 0.02 at a few MeV nuc−1. In an effort to evaluate the plausibility of the two explanations for Fe-rich SEP events, we studied the magnetic connection of the spacecraft to the solar source and the evolving CME; the velocity dispersion of the first arriving particles; and the time evolution of the Fe/O ratios. We also noted the pre-event CME and flare activity. We find that neither scenario is clearly consistent with the compositional variations between the four spacecraft, but more detailed modeling of the magnetic connections between the spacecraft and the solar source and the propagating shock may be beneficial.

Keywords: Solar energetic particles, Space weather
Exo─IPM Scattering as a Hidden Gatekeeper of Narrowband Technosignatures. Narrowband radio technosignatures can be significantly modulated by the host star's exoplanetary interplanetary medium (Exo-IPM), where turbulence in stellar winds and coronal mass ejections (CMEs) imprint spectral broadening. We present a novel framework that maps isotropic wind properties, turbulence strength, observing frequency, and geometry to the spectral broadening of narrowband technosignatures. Anchored to what is likely the largest compilation of empirical spectral-broadening measurements from solar-system spacecraft, we validate and derive a robust radial dependence of spectral broadening from the host star. For Sun-like stars, wind speeds and turbulence strengths are constrained directly from empirical measurements, while for M-dwarfs, these properties are scaled from solar values. Applied to a simulated 1 GHz survey of the nearest 106 stars across orbital properties, orientation, stellar population, and Exo-IPM conditions, the survival function indicates that ∼70% of systems produce &gt;1 Hz and &gt;30% produce &gt;10 Hz of broadening, disproportionately affecting M-dwarf systems, which constitute ∼75% of the stellar population. At 100 MHz, the effects are even more pronounced, with &gt;60% of systems exhibiting &gt;100 Hz of spectral broadening. Although the probability of encountering a CME during a typical technosignature observation is low (&lt;3%), nearly all such encounters induce additional broadening by several orders of magnitude (&gt;103 Hz). This redistribution of power from the expected intrinsic δ-like line into Lorentzian wings suppresses the peak signal-to-noise ratio targeted by standard narrowband pipelines, biasing sensitivity limits and plausibly contributing to the persistent "Great Silence" in narrowband radio technosignature searches over the past several decades.

Keywords: Interplanetary medium, Search for extraterrestrial intelligence, Technosignatures
Cosmological Prediction from the Joint Observation of MeerKAT and CSST at z = 0.4 ─ 1.2. Cross-correlating neutral hydrogen (H I) 21 cm intensity mapping with galaxy surveys provides an effective probe of astrophysical and cosmological information. This work presents a cross-correlation analysis between MeerKAT single-dish H I intensity mapping and Chinese Space Station Survey Telescope (CSST) spectroscopic galaxy surveys in z = 0.4 ─ 1.2, which will share a survey area of several thousand square degrees. Utilizing Jiutian-1G cosmological simulation, we simulate the observational data of MeerKAT and CSST with survey areas from ∼1600 to 600 deg2 at z = 0.5, 0.7, and 1. The effect of beam pattern, polarization leakage, and different foregrounds in the MeerKAT H I intensity mapping is considered in the simulation. After employing foreground removal with the principal component analysis method and performing signal compensation, we derive the cross-power spectra of MeerKAT and CSST. We perform the joint constraint using the CSST galaxy autopower spectra and MeerKAT-CSST cross-power spectra with the least-squares fitting method. The constraint results show that, in the simulated survey area, the relative accuracy can achieve 6% ─ 8% for the parameter products ΩHIbHIbgrHI,g and ΩHIbHIrHI,g at the three redshifts, which is 3 ─ 4 times smaller than the current result. These findings indicate that the full MeerKAT-CSST joint observation with thousands of square degrees overlapping survey area can be a powerful probe of large-scale structure, and has the ability to provide information on cosmic evolution of H I and galaxies in a wide redshift range.

Keywords: Cosmology, Cosmological parameters, Large-scale structure of the universe
Self-consistent Emission-line Diagnostics with Integrated Extinction Correction. We present a closed-form, self-consistent spectroscopic framework in which extinction correction is treated as an integral part of the inference rather than as a separate preprocessing step. From emission-line measurements alone, the method simultaneously solves for the electron density (ne), electron temperature (Te), extinction index (c(Hβ)), and total-to-selective extinction ratio (RV) within an adopted parametric family of extinction curves. The solution is obtained by minimizing the variance among c(Hβ) surfaces in the  logne ─ logTe  plane constructed from multiple line-ratio pairs, with RV treated as a free parameter, allowing the extinction law to be constrained directly from the data rather than fixed a priori. A simple rank condition, requiring n ≥ k + 4 lines for k ionic species, ensures the identifiability of unique solutions, while diagnostics based on the c(Hβ)-variance surface provide inexpensive quality control metrics. Noise-free tests recover input parameters exactly at grid points and to interpolation-limited accuracy off grid, validating the analytic formulation and its numerical implementation. When measurement uncertainty is introduced, a clear hierarchy of robustness emerges: plasma parameters remain accurate to ≲10% over wide ranges of line measurement precision, whereas extinction parameters require subpercent accuracy. For Balmer-line diagnostics, this implies a practical uncertainty threshold of ∼0.1%─0.2% per line for stable four-parameter recovery, while (ne, Te) alone remain informative at the 1%─2% level. This behavior follows from the geometric conditioning of the objective function surface, where noise flattens constrained directions. The framework clarifies how diagnostic geometry and diversity govern the solution stability in extinction-aware plasma diagnostics, from nebulae to integrated galaxy spectra.

Keywords: Observational astronomy, Plasma astrophysics, Chemical abundances, Extinction, Interstellar extinction, Astronomical methods
Ruling out Conventional Photoionization Models in the Closest LINER, M31, with CFHT/SITELLE Observations. The ionization mechanisms of low-ionization nuclear emission-line regions (LINERs), which are common in the local Universe, have been debated for decades. Our nearest large neighbor, M31, is classified as a LINER based on its optical emission-line properties within the central kiloparsec. In this work, we present a detailed photoionization modeling of the circumnuclear ionized gas in M31, explicitly tailored to its well-constrained physical conditions, including the absence of ongoing star formation and a currently inactive active galactic nucleus (AGN). Using spatially resolved CFHT/SITELLE observations, we find that photoionization by hot, evolved low-mass stars distributed throughout the bulge can roughly reproduce the observed radial intensity profiles of Hα, Hβ, and [N II]. However, these models fail to match the observed [O III] emission, producing radial profiles and [O III]/Hβ ratios that are significantly steeper than observed. This discrepancy indicates a deficit of high-energy ionizing photons in standard stellar photoionization models, even with extended ionizing sources. We explore whether this tension can be alleviated by invoking either a bulge-filling, low-density ionized medium surrounding a denser Hα-emitting disk or enhanced AGN activity in the recent past. While both scenarios can partially increase the [O III] emission, neither provides a fully satisfactory explanation under physically plausible conditions. Together with our earlier results for M81, these findings underscore persistent challenges in explaining LINER-like emission solely through conventional photoionization mechanisms.

Keywords: Galaxy spectroscopy, Photoionization, Active galactic nuclei, Galaxy nuclei
Helium Escape in Context: Comparative Signatures of Four Close-in Exoplanets. Observations of escaping atmospheres on close-in exoplanets show a wide range in the strength and morphology of He I 10830 Å and H I absorption. Scaling relations attempt to link the He I signal to X-ray and UV irradiation, mass loss, and bulk planetary parameters. We test these relations with a comparative analysis of HD209458b, HD189733b, HD149026b, and GJ1214b using a 1D hydrodynamic, multispecies, full-atmosphere escape model. For the benchmark HD209458b, our previously validated solution reproduces the observed He I and Hα transit depths without imposing composition constraints. HD189733b exhibits comparable He I depths, but the broadest reported profiles require ∼12 km s−1 of additional nonthermal broadening, whereas more recent measurements are narrower, consistent with our predictions. For HD149026b, despite similar system properties, our model shows that higher gravity suppresses escape and enhances diffusive separation, depleting helium at high altitudes and yielding extremely weak He I absorption. For the sub-Neptune GJ1214b, H/He-only models overestimate He I absorption; including H2 and its ions (H 2+ , H 3+ , HeH+) lowers the escape rate and modifies the ion/electron balance, reducing the metastable helium densities. Compared against scaling relations, HD189733b observations and our HD149026b prediction fall below the trend, whereas some observations of HD209458b and GJ1214b are consistent; however, the observed transit depths are variable. Across all targets, we find diffusive separation of helium and hydrogen, which may explain why subsolar He/H ratios are often required in simplified models. We conclude that interpreting He I and Hα absorption requires first-principles models that include self-consistent temperature and velocity profiles, multispecies transport, and molecular chemistry.

Keywords: Exoplanet atmospheric dynamics, Exoplanet atmospheric variability, Exoplanet atmospheric evolution, Exoplanet atmospheres, Exoplanet atmospheric structure
Determining the Spatial Origin of X-Ray and Optical Emission in the z = 3.1 Strongly Lensed Radio-quiet Quasar GraL J065904.1+162909 to Hundreds of Parsecs. We perform milliarcsecond X-ray astrometry of the quadruply lensed radio-quiet quasar GraL J065904.1+162909 (J0659). This zs = 3.083 quasar is lensed into four images and was discovered with the second Data Release of the Gaia Space Observatory (Gaia DR2). Our J0659 study exploits strong gravitational lenses as high-resolution telescopes. This technique shows promise to elucidate the origin of optical and X-ray emission in distant lensed quasars at spatial scales beyond the reach of current instruments. In our study, we use Gaia DR3 and Hubble Space Telescope observations of J0659 to infer a mass model for the deflector. Our model reproduces the Gaia DR3 quasar lensed image positions to one milliarcsecond and determines the position of the optical source in J0659 to within this precision. Next, we analyze Chandra observations of J0659 and conduct a Bayesian test evaluating whether the X-ray emission region coincides with the optical source. We then constrain the origin of the X-ray emission to within a  0.″020  ×  0.″010  ellipse centered  0.″014  away from the optical source at the 1σ level. We demonstrate that our approach can be extended to pinpoint the distinct locations of the soft and hard X-ray emission regions in lensed quasars. We discuss the potential of upcoming broadband and spectrally resolved X-ray astrometric studies to probe complex quasar morphology and multiplicity of active galactic nuclei at subkiloparsec scales otherwise inaccessible at high redshifts.

Keywords: X-ray astronomy, Black hole physics, High energy astrophysics, Strong gravitational lensing, Active galactic nuclei, Galaxies
From Common Envelope Evolution to Luminous Red Novae. I. A One-dimensional Radiation Hydrodynamic Model. The acceleration and unbinding of the common envelope during the plunge-in phase are governed by complex physical processes that often manifest observationally as luminous red novae. We investigate the dynamics of this phase using one-dimensional radiation hydrodynamic simulations evolved with the code Guangqi. We perform a parameter survey to quantify the impact of key physical conditions on the unbound mass fraction, η, and the resulting light curves. Our survey spans a range of radiation-to-gas internal energy ratios ( E/eg∈[0.2,3.2] ), ratios of total envelope energy to gravitational binding energy (ζ ∈ [0.54, 2.87]), and mass injection rates ( Ṁ∈[2.5,10]M⊙yr-1 ), while covering both subsonic and supersonic expansion regimes (vej/vesc ∈ [0.3, 0.6]). We demonstrate that: (1) radiation pressure becomes the dominant driver of mass ejection in the high-opacity, high-luminosity region immediately below the recombination front; (2) η exhibits a nonlinear dependence on ζ, which is modulated by the mass injection rate and gravitational potential; and (3) the recombination of atomic to molecular hydrogen (H → H2) releases latent heat that sustains a secondary plateau in the late-time light curve. These findings are substantiated by detailed error analysis and convergence testing presented in the Appendices.

Keywords: Hydrodynamical simulations, Common envelope evolution
Orbital Motions of Binaries in Orion South. We present high-angular resolution ( ≃0.″06 ) Very Large Array and Atacama Large Millimeter/submillimeter Array observations of Orion South separated by 15.52 yr. The purpose of this study was to search for orbital motions in three close ( ≃0.″1 ) binary systems in the region. We do not detect changes in the position angle of the binaries, but in two of the cases, we detect significant changes in their separation in the plane of the sky. We use these changes to estimate that the total mass of the binaries is in the ≃1─2 M⊙ range. We also estimate the disk masses from the millimeter emission. The disk-to-stellar mass ratio is in the range of 0.04─0.18, values consistent with those expected for very early stellar evolution (Class 0) protostars.

Keywords: Binary stars, Protoplanetary disks, Stellar masses