Sazuna/UAT_keywords huggingface dataset:
First Polarimetric View of GX 349+2 with the Imaging X-Ray Polarimetry Explorer. We conducted a spectropolarimetric study of the bright Z source GX 349+2 using the Imaging X-ray Polarimetry Explorer (IXPE) observation. Our findings reveal a significant polarization degree (PD) of 1.1% ± 0.3% in the 2.0–8.0 keV energy range. Spectropolarimetric analysis was performed by modeling the source spectra with an absorbed multicolor disk component and a blackbody. This allowed us to constrain the polarization contributions from the disk and boundary/spreading layer. The results indicate that the observed polarization signal primarily originates from the disk and the spreading layer at the neutron star's surface, rather than the boundary layer. Additionally, we detect an excess polarization component, which we attribute to either an outflow or reflection processes within the system, indicating the presence of a third component, albeit not observed in the IXPE spectra. Furthermore, energy-resolved polarization analysis in the 2.0–4.0 and 4.0–8.0 keV energy ranges hinted at a marginal increase of PD with energy and rotation of polarization angle (PA). This also pointed to an energy-dependent dominance of emission and indicated that the variation in PA with energy (∼17∘ in the 2.0–4.0 keV energy range and ∼48∘ in the 4.0–8.0 keV energy range) is likely associated with the different nonorthogonal PAs of the disk and spreading layer components, which peak at different energies.

Keywords: Accretion, Neutron stars, Spectropolarimetry, Low-mass x-ray binary stars, Stellar accretion disks, Polarimetry
Anisotropic Particle Acceleration in Alfvénic Turbulence. Alfvénic turbulence is an effective mechanism for particle acceleration in strongly magnetized, relativistic plasma. In this study, we investigate a scenario where turbulent plasma is influenced by a strong guide magnetic field, resulting in highly anisotropic turbulent fluctuations. In such cases, the magnetic moments of particles are conserved, which means that acceleration can only occur along the direction of the magnetic field. Consistent with previous analytic studies, we find through particle-in-cell simulations of magnetically dominated pair plasma that the momenta of accelerated particles are closely aligned with the magnetic field lines. Notably, the alignment angle decreases as particle energy increases, potentially limited only by the inherent curvature and gradients of the turbulent magnetic fluctuations. This finding has significant implications for interpreting the synchrotron radiation emitted by highly accelerated particles.

Keywords: Plasma astrophysics, High energy astrophysics, Plasma physics
The Kinematic Signature of the Warp and Waves in the Milky Way Disk. Using over 170,000 red clump (RC) stars selected from LAMOST and APOGEE, we conduct a detailed analysis of the stellar VZ as a function of LZ (or Rg) across different ϕ bins for various disk populations. The VZ of the whole RC sample stars exhibits a wavelike pattern superimposed on an exponentially increasing trend, indicating the contribution from disk warp, disk flare, and disk waves. Our results across various populations suggest that the thin disk is similar to the whole RC sample behavior, while the thick disk displays a wavelike pattern superimposed on a linearly increasing trend, meaning that the features of disk warp and waves are present in both thin and thick disks, and the disk flare feature is only present in the thin disk. These results indicate that the disk warp is potentially driven by secular processes like disk perturbations from intergalactic magnetic fields and a misaligned dark halo. The line-of-node of the disk warp of various populations displays a slight difference, with ϕ0 = 5 .° 68 ± 2 .° 91 for the whole RC sample of stars, ϕ0 = 5 .° 78 ± 2 .° 89 for the thin disk stars, and ϕ0 = 4 .° 10 ± 3 .° 43 for the thick disk stars.

Keywords: Stellar kinematics, Stellar abundances, Galaxy dynamics, Galaxy structure, Milky Way disk, Galaxy kinematics
Quantifying the Limits of TESS Stellar Rotation Measurements with the K2-TESS Overlap. The Transiting Exoplanet Survey Satellite (TESS) has provided stellar rotation periods across much of the sky through high-precision light curves, but the reliability and completeness of these measurements require careful evaluation. We assess the accuracy of TESS-derived rotation periods by leveraging a cross-matched sample of ∼23,000 stars observed by both TESS and the K2 mission, treating K2 periods as a benchmark. Using causal pixel models to extract light curves and a Lomb–Scargle (LS) periodogram to identify rotation signals, we quantify the empirical uncertainties, reliability, and completeness of TESS rotation period measurements. We find that uncertainties on TESS-derived rotation periods are typically below 3% for stars with periods &lt;10 days. Rotation periods are generally reliable out to 10 days, with ≳80% of measurements matching the K2 benchmark. Completeness and reliability drop dramatically for periods beyond ≃12 days due to the 27 day sector limitation. Stricter cuts on TESS magnitude and LS power improve reliability; the highest LS power tested (&gt;0.2) ensures &gt;90% reliability below 10 days but removes over half of potential detections. Stitching consecutive-sector light curves reduces period uncertainties but does not improve overall reliability or completeness due to persistent systematics. Our findings and code provide a framework for interpreting TESS-derived rotation periods and inform the selection of quality cuts to optimize studies of stellar rotation, young associations, and gyrochronology.

Keywords: Open star clusters, Stellar rotation
r-process Nucleosynthesis and Radioactively Powered Transients from Magnetar Giant Flares. We present nucleosynthesis and light-curve predictions for a new site of the rapid neutron capture process (r-process) from magnetar giant flares (GFs). Motivated by observations indicating baryon ejecta from GFs, J. Cehula et al. proposed that mass ejection occurs after a shock is driven into the magnetar crust during the GF. We confirm using nuclear reaction network calculations that these ejecta synthesize moderate yields of third-peak r-process nuclei and more substantial yields of lighter r-nuclei, while leaving a sizable abundance of free neutrons in the outermost fastest expanding ejecta layers. The final r-process mass fraction and distribution are sensitive to the relative efficiencies of α-capture and n-capture freeze-outs. We use our nucleosynthesis output in a semianalytic model to predict the light curves of novae breves, the transients following GFs powered by radioactive decay. For a baryonic ejecta mass similar to that inferred of the 2004 Galactic GF from SGR 1806-20, we predict a peak UV/optical luminosity of ∼1039–1040 erg s‑1 at ∼10–15 minutes, rendering such events potentially detectable to several Mpc following a gamma-ray trigger by wide-field transient monitors such as ULTRASAT/UVEX. The peak luminosity and timescale of the transient increase with the GF strength due to the larger ejecta mass. Although GFs likely contribute 1%–10% of the total Galactic r-process budget, their short delay-times relative to star formation make them an attractive source to enrich the earliest generations of stars.

Keywords: Soft gamma-ray repeaters, R-process, Transient sources
Revealing the Spectral Properties of Magnetic Turbulence by Synchrotron Polarization Gradients. Based on the modern understanding of MHD turbulence theory, we propose a new method for measuring the spectral properties of magnetic turbulence by synchrotron polarization gradient analysis. Using synthetic polarization observational data, we first confirm the feasibility of the gradient technique to determine the scaling properties of magnetic turbulence. We then apply this technique to the Galactic plane survey data from the Australia Telescope Compact Array and obtain the power-law spectral feature of the Galactic magnetic turbulence of E ∝ k‑10/3. Gradient techniques open up a new way to obtain spectral properties of magnetic turbulence from polarization observations, such as the Low-Frequency Array for Radio Astronomy, in the presence of low-frequency and strong Faraday depolarization.

Keywords: Magnetohydrodynamics, Interplanetary turbulence, Astrophysical magnetism, Interstellar emissions, Interstellar synchrotron emission
On the Stability of Interstellar Neutral Hydrogen Clouds at Large Z-heights. Galactic neutral hydrogen (H I) data drawn from several large-scale surveys have been used to study 32 small clouds found between Galactic longitudes 70° and 140° and latitudes ‑20° and ‑45°. This places them below the Perseus spiral arm in the second quadrant of Galactic longitude. The velocities of the sample range from ‑30 to ‑57 km s‑1, and their z-heights are between ‑1.5 and ‑3.7 kpc. The mapped clouds are localized brightness enhancements along the length of interstellar H I filaments. This H I may have been propelled into the Galactic halo by the action of many supernovae and stellar winds originating in the abundant star-forming regions in this longitude region of the Perseus spiral arm. Adopting this model allows the distance to each cloud to be derived. Their emission profiles are characterized by narrow lines ≈5 km s‑1 wide. Application of the virial theorem for the ensemble of features indicates that an average magnetic field of 1.0 ± 0.4 μG can balance internal pressure.

Keywords: Diffuse interstellar clouds
Tracking an Eruptive Intermediate Prominence Originating from the Farside of the Sun. In this paper, we carry out multiwavelength and multiview observations of the eruption of an intermediate prominence originating from the farside of the Sun on 2023 March 12. The southeast footpoint of the prominence is located in NOAA Active Region 13252. The eruption generates a B7.8 class flare and a partial halo coronal mass ejection (CME). The prominence takes off at 02:00 UT and accelerates for nearly 3 hr. Rotation of the southeast leg of the prominence in the counterclockwise direction is revealed by spectroscopic and imaging observations. The apex of the prominence changes from a smooth loop to a cusp structure during the rising motion, and the northwest leg displays a drift motion after 04:30 UT, implying a writhing motion. Hence, the prominence eruption is most likely triggered by ideal kink instability. For the first time, we apply the Graduated Cylindrical Shell modeling in 3D reconstruction and tracking of the prominence for nearly 2 hr. Both the source region (110°E, 43°N) and northwest footpoint (162°E, 44°N) are located. The edge-on and face-on angular widths of the prominence are ∼6° and ∼86°, respectively. The axis has a tilt angle of ∼70° with the meridian. The heliocentric distance of the prominence leading edge increases from ∼1.26 R⊙ to ∼2.27 R⊙. The true speed of the CME increases from ∼610 to ∼849 km s‑1.

Keywords: Solar coronal mass ejections, Solar flares, Solar prominences
High-density Symmetry Energy: A Key to the Solution of the Hyperon Puzzle. The recently developed nuclear effective interaction based on the so-called N3LO Skyrme pseudopotential is extended to include hyperon–nucleon and hyperon–hyperon interactions by assuming similar density, momentum, and isospin dependence as for the nucleon–nucleon interaction. The parameters in these interactions are determined from either experimental information, if any, or chiral effective field theory or lattice quantum chromodynamics calculations of the hyperon potentials in nuclear matter around nuclear saturation density ρ0. We find that varying the high-density behavior of the symmetry energy Esym(ρ) can significantly change the critical density for hyperon appearance in neutron stars and thus the maximum mass MTOV of static hyperon stars. In particular, a symmetry energy that is soft around 2ρ0–3ρ0 but stiff above about 4ρ0 can lead to MTOV ≳ 2 M⊙ for hyperon stars and simultaneously be compatible with (1) the constraints on the equation of state of symmetric nuclear matter at suprasaturation densities obtained from flow data in heavy-ion collisions; (2) the microscopic calculations of the equation of state for pure neutron matter; (3) the tidal deformability of stars extracted from gravitational wave signal GW 170817; (4) the mass–radius relations of PSR J0030+0451, PSR J0740+6620, and PSR J0437-4715 measured from NICER; and (5) the observation of an unusually low mass and small radius in the central compact object of HESS J1731-347. Furthermore, the squared sound speed of the hyperon star matter naturally displays a strong peak structure around a baryon density of 3ρ0–4ρ0, consistent with a model-independent analysis of the multimessenger data. Our results suggest that the high-density symmetry energy could be a key to the solution of the hyperon puzzle in neutron star physics.

Keywords: Neutron stars
Evidence of Minijet Emission in a Large Emission Zone from a Magnetically Dominated Gamma-Ray Burst Jet. The second brightest gamma-ray burst (GRB) in history, GRB 230307A, provides an ideal laboratory to study the mechanism of GRB prompt emission thanks to its extraordinarily high photon statistics and its single-episode activity. Here we demonstrate that the rapidly variable components of its prompt emission compose an overall broad single pulse-like profile. Although these individual rapid components are aligned in time across all energy bands, this overall profile conspires to show a well-defined energy-dependent behavior that is typically seen in single GRB pulses. Such a feature demonstrates that the prompt emission of this burst is from many individual emitting units that are casually linked in a emission site at a large distance from the central engine. Such a scenario is in natural consistency with the internal-collision-induced magnetic reconnection and turbulence framework, which invokes many minijets due to local magnetic reconnection that constantly appear and disappear in a global magnetically dominated jet.

Keywords: Gamma-ray transient sources, Gamma-ray bursters
Evolution of the Inner Accretion Flow and the White Dwarf Spin Pulse during the 2023 Outburst in GK Persei. We present our X-ray and optical observations performed by NICER, NuSTAR, and Tomo-e Gozen during the 2023 outburst in the intermediate polar GK Persei. The X-ray spectrum consisted of three components: blackbody (BB) emission of several tens of eVs from the irradiated white dwarf (WD) surface, a source possibly including several emission lines around 1 keV, and multitemperature bremsstrahlung emission from the accretion column. The 351.3 s WD spin pulse was detected in X-rays, and the observable X-ray flux from the column drastically decreased at the off-pulse phase, which suggests that the absorption of the column by the accreting gas, called the curtain, was the major cause of the pulse. As the system became brighter in the optical, the column became fainter, the pulse amplitude became higher, and the energy dependence of pulses became weaker at &lt;8 keV. These phenomena could be explained by the column's more pronounced absorption by the denser curtain as mass-accretion rates increased. The BB and line fluxes rapidly decreased at the optical decline, which suggests the expansion of the innermost disk edge with decreasing accretion rates. The electron scattering or the column geometry may be associated with the almost no energy dependence of high-energy pulses. The irradiated vertically thick structure at the disk may generate optical quasi-periodic oscillations with a period of ∼5700 s.

Keywords: Dwarf novae, DQ Herculis stars, X-ray sources, Stellar accretion disks, Cataclysmic variable stars
The BTSbot-nearby Discovery of SN 2024jlf: Rapid, Autonomous Follow-up Probes Interaction in an 18.5 Mpc Type IIP Supernova. We present observations of the Type IIP supernova (SN) SN 2024jlf, including spectroscopy beginning just 0.7 days (∼17 hr) after first light. Rapid follow-up was enabled by the new BTSbot-nearby program, which involves autonomously triggering target-of-opportunity requests for new transients in Zwicky Transient Facility data that are coincident with nearby (D &lt; 60 Mpc) galaxies and identified by the BTSbot machine learning model. Early photometry and nondetections shortly prior to first light show that SN 2024jlf initially brightened by &gt;4 mag day−1, quicker than ∼90% of Type II SNe. Early spectra reveal weak flash ionization features: narrow, short-lived (1.3 &lt; τ[days] &lt; 1.8) emission lines of Hα, He II, and C IV. Assuming a wind velocity of vw = 50 km s−1, these properties indicate that the red supergiant progenitor exhibited enhanced mass loss in the last year before explosion. We constrain the mass-loss rate to  10−4&lt;Ṁ[M⊙yr−1]&lt;10−3  by matching observations to model grids from two independent radiative hydrodynamics codes. BTSbot-nearby automation minimizes spectroscopic follow-up latency, enabling the observation of ephemeral early-time phenomena exhibited by transients.

Keywords: Sky surveys, Core-collapse supernovae, Type II supernovae, Transient sources, Time domain astronomy, Spectroscopy
Secular Evolution of Quasiperiodic Eruptions. Quasiperiodic eruptions (QPEs) are intense, repeating soft X-ray bursts with recurrence times about a few hours to a few weeks from galactic nuclei. More and more analyses show that QPEs are the result of collisions between a stellar mass object (SMO; a stellar mass black hole or a main-sequence star) and an accretion disk around a supermassive black hole (SMBH) in galactic nuclei. In this work, we propose an osculating trajectory method for efficiently calculating secular evolution of extreme mass ratio inspirals (EMRIs) that are perturbed by an accretion disk. This method accelerates the calculation of EMRI orbital evolution by orders of magnitude and lays the foundation for analyzing long-term QPE observations. Applying this method to orbital analyses of GSN 069 and eRO-QPE2, the two most stable QPE sources, we find informative constraints on the SMBH mass, the radiation efficiency of QPEs, the SMO nature, the accretion disk surface density, and the accretion disk viscosity. Combining all the QPE sources available, we find the QPE EMRIs can be divided into two populations according to their orbital eccentricities, where the orbital periods and the SMBH masses in the low-eccentricity population follow a scaling relation of  Tobt∝M•n  with n ≈ 0.8.

Keywords: Supermassive black holes, Apsidal motion, Tidal disruption, Active galactic nuclei, General relativity, Keplerian orbit
The ALMA-CRISTAL Survey: Weak Evidence for Star-formation-driven Outflows in z ∼ 5 Main-sequence Galaxies. There is a broad consensus from theory that stellar feedback in galaxies at high redshifts is essential to their evolution, alongside conflicting evidence in the observational literature about its prevalence and efficacy. To this end, we utilize deep, high-resolution [C II] emission-line data taken as part of the [C II] resolved interstellar medium (ISM) in star-forming galaxies with the Atacama Large Millimeter/submillimeter Array (CRISTAL) survey. Excluding sources with kinematic evidence for gravitational interactions, we perform a rigorous stacking analysis of the remaining 15 galaxies to search for broad emission features that are too weak to detect in the individual spectra, finding only weak evidence that a broad component is needed to explain the composite spectrum. Additionally, such evidence is mostly driven by CRISTAL-02, which is already known to exhibit strong outflows in multiple ISM phases. Interpreting modest residuals in the stack at v ∼ 300 km s−1 as an outflow, we derive a mass outflow rate of  Ṁout  = 26 ± 11 M⊙ yr−1 and a cold outflow mass-loading factor of ηm = 0.49 ± 0.20. This result holds for the subsample with the highest star formation rate surface density (ΣSFR &gt; 1.93 M⊙ yr−1 kpc−2), but no such broad component is present in the composite of the lower-star-formation-rate density subsample. Our results imply that the process of star-formation-driven feedback may already be in place in typical galaxies at z = 5, but on average are not strong enough to completely quench ongoing star formation.

Keywords: High-redshift galaxies, Galaxy kinematics, Galaxy evolution, Stellar feedback
Density Profiles of TNG 300 Voids across Cosmic Time. We present radial density profiles, as traced by luminous galaxies and dark matter particles, for voids in 11 snapshots of the TNG 300 simulation. The snapshots span 11.65 Gyr of cosmic time, corresponding to the redshift range 0 ≤ z ≤ 3. Using the comoving galaxy fields, voids were identified via a well-tested, watershed transformation-based algorithm. Voids were defined to be underdense regions that are unlikely to have arisen from Poisson noise, resulting in the selection of ∼100–200 of the largest underdense regions in each snapshot. At all redshifts, the radial density profiles as traced by both the galaxies and the dark matter resemble inverse top-hat functions. However, details of the functions (particularly the underdensities of the innermost regions and the overdensities of the ridges) evolve considerably more for the dark matter density profiles than for the galaxy density profiles. At all redshifts, a linear relationship between the galaxy and dark matter density profiles exists, and the slope of the relationship is similar to the bias estimates for TNG 300 snapshots. Lastly, we identify distinct environments in which voids can exist, defining "void-in-void" and "void-in-cloud" populations (i.e., voids that reside in larger underdense or overdense regions, respectively), and we investigate ways in which the relative densities of dark matter and galaxies in the interiors and ridges of these structures vary as a function of void environment.

Keywords: Magnetohydrodynamical simulations, Voids, Cosmic web, Large-scale structure of the universe
X-Ray and Radio Polarimetry of the Neutron Star Low-mass X-Ray Binary 4U 1728─34. We report the first X-ray and radio polarimetric results of the neutron star (NS) low-mass X-raydis binary atoll-source 4U 1728−34 using the Imaging X-ray Polarimetry Explorer (IXPE) and Australia Telescope Compact Array. We discovered that the X-ray source was polarized at PD = 1.9% ± 1.0% with a polarization angle of PA = −41° ± 16°. Simultaneous Neutron Star Interior Composition Explorer observations show that the source was in a relatively hard state, marking it as the first IXPE observation of an NS atoll source in the hard state. We do not detect any significant linear polarization in the radio band, with a 3σ upper limit of 2% at 5.5 GHz and 1.8% at 9 GHz. Combining the radio data sets provides the deepest upper limits on the radio polarization at &lt;1.5% on the linear and circular polarization (measured at 7.25 GHz). The X-ray polarimetric results suggest a source geometry with a Comptonization component possibly attributed to a boundary layer emission or BL emission reflected off the disk , consistent with the other NS atoll sources.

Keywords: Neutron stars, Accretion, X-ray binary stars, Low-mass x-ray binary stars, Polarimetry