Sazuna/UAT_keywords huggingface dataset:
A NICER View of the 1.4 M<SUB>⊙</SUB> Edge-on Pulsar PSR J0614-3329. Four neutron star radius measurements have already been obtained by modeling the X-ray pulses of rotation-powered millisecond pulsars observed by the Neutron Star Interior Composition ExploreR (NICER). We report here the radius measurement of PSR J0614−3329 employing the same method with NICER and XMM-Newton data using Bayesian inference. For all different models tested, including one with unrestricted inclination prior, we retrieve very similar nonantipodal hot region geometries and radii. For the preferred model, we infer an equatorial radius of  Req=10.29−0.86+1.01 km for a mass of  M=1.44−0.07+0.06M⊙  (median values with equal-tailed 68% credible interval), the latter being essentially constrained from radio timing priors obtained by MeerKAT. A more complex model, fitting the data equally well, resulted in a consistent inferred radius. We find that, for all different models, the pulse emission originates from two hot regions, one at the pole and the other at the equator. The resulting radius constraint is consistent with previous X-ray and gravitational wave measurements of neutron stars in the same mass range. Equation of state inferences, including previous NICER and gravitational wave results, slightly soften the equation of state with PSR J0614−3329 included and shift the allowed mass─radius region toward lower radii by ∼300 m, which is compatible with previous analyses to within less than one standard deviation.

Keywords: X-ray astronomy, Neutron stars, Neutron star cores, Millisecond pulsars
A Late-time Radio Search for Highly Off-axis Jets from PTF Broad-lined Ic Supernovae in GRB-like Host Galaxy Environments. Hydrogen/helium-poor stripped-envelope core-collapse supernovae with broad lines (SNe Ic-bl) almost always accompany the nearby (z &lt; 0.3) jetted relativistic explosions known as long duration gamma-ray bursts (GRBs). However, the majority of SNe Ic-bl have no detected GRB counterpart. At least some of these SNe should harbor off-axis jets, whose afterglow may become detectable at late times, particularly at radio wavelengths. Here, we present Karl G. Jansky Very Large Array (VLA) radio observations (rest-frame times of ∼3─4 × 103 days post SN discovery) of a sample of 14 SNe Ic-bl discovered by the Palomar Transient Factory (PTF) that have been demonstrated to originate from the same host environments as the SNe Ic-bl associated with nearby GRBs. Of the 14 SNe, we identify three that are radio detected, one of which (PTF10tqv, z = 0.0795) is consistent with an off-axis jet with energy similar to classical GRBs (∼1051─1051.7 erg). Using recently developed synchrotron radiation code, we find that for our 11 nondetections, which are among the deepest limits obtained for Ic-bl, we rule out an off-axis jet with an energy of ≳1051 erg in circumburst densities of ≳10−1 cm−3. We predict that well-spaced monitoring of newly discovered SNe Ic-bl from ∼10 days to ∼10 yr (rest frame) to luminosities of ∼1027 erg s−1 Hz−1 will constrain the existence of highly off-axis jets (≳60°) with classical GRB energies. The VLA Sky Survey will probe jets that are ≲60° off-axis, whereas the Deep Synpotic Array 2000 will probe jets out to ∼90° off-axis, demonstrating the importance of utilizing radio surveys to supplement targeted observations.

Keywords: Gamma-ray bursts, High energy astrophysics, Core-collapse supernovae, Relativistic jets, Time domain astronomy, Radio astronomy
Reassessing the ZTF Volume-limited Type Ia Supernova Sample and Its Implications for Continuous, Dust-dependent Models of Intrinsic Scatter. The volume-limited low-redshift SNe Ia sample made available by ZTF DR2 is excellent for studying a central question for analyses of SNe Ia—whether the remaining diversity of standardized luminosities arises in part from an intrinsic or extrinsic effect—characterized by the color-independent bimodality in progenitor population or color- and host-dependent diversity in dust extinction, for instance. In the initial analyses from the ZTF Collaboration, the authors reported evidence for the former hypothesis, in contrast to much of the previous evidence for the dust hypothesis found across other SNe Ia samples. We reanalyze this ZTF sample (458 SNe after cuts) in the same manner as previous samples, and report consistency with trends seen in the literature, in support of the dust hypothesis. We find the following: (1) a color dependency in the canonical "mass-step" size for SNe, with red SNe having a larger host-dependent residual step than blue SNe by 0.18 ± 0.09 mag; (2) a color-dependent difference in the Hubble residual scatter, with red SNe having a ∼33% larger scatter than blue SNe at &gt;3σ significance; (3) data's preference of a model that accounts for color-dependency over a simple "step" model at ∼3σ; (4) the strongest evidence to date (3.5σ) that the relationship between supernova color, host-galaxy properties, and luminosity is continuous rather than a discrete step. Accounting for (3) and (4) with our new model, Host2D, yields a 4.0σ improvement over the mass step model. We trace the difference in reported findings to the analysis methods, rather than a difference in the sample itself.

Keywords: Galaxy properties, Observational cosmology, Standard candles, Multivariate analysis, Type Ia supernovae
Plasma Wave-particle Acceleration as the Origin of the Galactic Gamma-Ray Bubbles. The "Fermi bubbles" are two giant gamma-ray emitting configurations in the form of bubbles that extend above and below the Galactic plane. They are characterized by a smooth surface, sharp edges, and an almost flat intensity distribution. They were discovered in 2010 by the Fermi telescope and detected in the energy range 1─100 GeV. We propose a novel theoretical model to explain the process involved in the "Fermi bubbles" phenomenon. The model is based on the "in situ" generation of an energetic electron population powered by unstable electromagnetic waves triggered by a nonrelativistic outflow of matter escaping from the Galactic center region. A hadronic outflow crossing the magnetic field in the Galactic halo of low-density plasma can induce an electromagnetic instability in the "lower hybrid" frequency range (between the ion and electron cyclotron frequencies). These lower hybrid waves propagate along the magnetic field lines in the halo and can accelerate, via resonant Landau damping, the thermal electrons up to energies on the order of hundreds of GeV. This energetic electron population, localized in a thin boundary layer of the halo, radiates by synchrotron emission and by inverse Compton scattering. An evaluation of the radiation emission and a comparison with spectral data is presented. This model successfully explains in a natural way the GeV spectral properties of the "Fermi bubbles" as well as their microwave emission.

Keywords: Gamma-ray sources, Space plasmas, Plasma astrophysics, Milky Way Galaxy
The Feasibility of a Spacecraft Flyby with the Third Interstellar Object 3I/ATLAS from Earth or Mars. We investigate the feasibility of a spacecraft mission to conduct a flyby of 3I/ATLAS, the third macroscopic interstellar object discovered on 2025 July 1, as it traverses the solar system. There are both ready-to-launch spacecraft currently in storage on Earth, such as Janus, and spacecraft nearing the end of their missions at Mars. We calculate minimum ∆V single-impulse direct transfer trajectories to 3I/ATLAS both from Earth and from Mars. We consider launch dates spanning 2025 January through 2026 March to explore obtainable and hypothetical mission scenarios. Postdiscovery Earth departures require a challenging ∆V ≳ 24 km s−1 to fly by 3I/ATLAS. By contrast, Mars departures from 2025 July to 2025 September require ∆V ∼ 5 km s−1 to achieve an early October flyby—which is more feasible with existing propulsion capabilities. We further calculate the phase angle and flyby velocity for these trajectories, noting that the resulting flyby speeds would impose significant observational and engineering challenges that a mission would need to overcome. We discuss how existing spacecraft could be used to observe 3I/ATLAS and how spacecraft at other locations in the solar system could be repurposed to visit future interstellar objects on short notice.

Keywords: Comets, Asteroids, Flyby missions, Interstellar objects
Supersonic Turbulence in Primordial Halos: a Comparison with and without the Stream Velocity. Turbulence plays a critical role in regulating star formation in molecular clouds and is also observed in simulations of primordial halos that host Population III (Pop III) stars. The relative velocity between baryons and dark matter at the time of recombination is thought to be a source of turbulence in the early Universe. In this paper, we study how this stream velocity affects the turbulence inside primordial halos using high-resolution cosmological simulations across the redshift range of z = 30 to z = 20. We find that at a fixed redshift, the stream velocity enhances turbulence in low-mass halos (M ≲ 106 M⊙) and suppresses it for high-mass halos (M ≳ 106 M⊙). The enhancement in low-mass halos likely arises from residual kinetic energy introduced by the stream velocity, while the suppression in high-mass halos likely arises from a reduction in accretion-driven turbulence. This mass-dependent modulation of turbulence suggests that the initial conditions inside primordial halos are altered in the presence of the stream velocity, potentially influencing their fragmentation and the resulting star formation.

Keywords: Cosmology, Hydrodynamical simulations, Galaxy formation, Population III stars, Star formation, High-redshift galaxies
Fermi-LAT Captures a Late-2024 Gamma-Ray Outburst near Two Newly Identified Gamma-Ray-emitting Galactic Supernova Remnants, without Evidence of Physical Association. We report the gamma-ray study of two neighboring in the sky Galactic supernova remnants (SNRs), namely, 3C 434.1 (or G094.0+01.0) and G093.7─00.2. In the vicinity of the two SNRs, a late-2024 gamma-ray outburst—not physically connected to the SNRs—was detected with the Fermi Large Area Telescope (LAT). Employing 16.5 yr of Fermi-LAT data, we report the first firm detection of the gamma-ray counterpart of 3C 434.1 at a 7.2σ significance and a likely detection of an enhanced gamma-ray emission signal at a 4.5σ level from G093.7─00.2. The late-2024 gamma-ray outburst is detected at a ∼12σ significance level over a duration of 3 days. For all three objects, a comprehensive morphological and spectral analysis of the corresponding gamma-ray data was conducted. The prevalent scenario for the nature of the gamma-ray emission of both SNRs is attributed to their surrounding environment. Both are likely interacting with nearby dense material, resulting in hadronically induced gamma-ray emission. We deduce that the outburst source is most likely a blazar in flare, linked to the compact, flat-spectrum radio source TXS 2138+527 (also known as NVSS J213953+530016). Further, the spectral analysis of the gamma-ray source conducted within the 100 MeV─800 GeV energy range using the complete LAT data sets, which yielded a soft averaged spectral shape, supports the hypothesis of a flat spectrum radio quasar (FSRQ) origin for the source; with a most likely leptonically induced scenario for the observed gamma-ray outburst as inferred from the obtained hard spectral shape when utilizing short time intervals focusing on the outburst.

Keywords: Supernova remnants, Blazars, Gamma-ray sources, High energy astrophysics
Detection of CH<inline-formula> <mml:math><mml:msubsup><mml:mrow></mml:mrow><mml:mrow><mml:mn>3</mml:mn></mml:mrow><mml:mrow><mml:mo>+</mml:mo></mml:mrow></mml:msubsup></mml:math> </inline-formula> in the O-rich Planetary Nebula NGC 6302. Planetary nebulae are sites where ejected stellar material evolves into complex molecules, but the precise physical conditions and chemical routes that govern these processes are unclear. The presence of abundant carbon-rich molecules in O-rich environments poses particular challenges. Here we report the first detection of methyl cation (CH 3+ ) in any planetary nebula, observed in the O-rich nebula NGC 6302 using JWST MIRI/Medium Resolution Spectrometer observations. CH 3+  is a key driver of organic chemistry in UV-irradiated environments. Spatially resolved observations reveal that CH 3+  is colocated with 12CO, H2, H II, HCO+, and polycyclic aromatic hydrocarbons. LTE modeling of the CH 3+  emission yields excitation temperatures of 500─800 K in the inner bubble and torus, rising to 1000─2000 K in the outer bubble of NGC 6302, with column densities ranging from ∼1011 to 1013 cm−2. This detection suggests that hydrocarbon radical chemistry must be incorporated into planetary nebulae chemical models. Further near-IR observations are crucial to map different chemical networks operating in these environments.

Keywords: Planetary nebulae, Astrochemistry, Small molecules, Circumstellar gas
Hot, Cold, and Multicomponent Accretion Flows around Supermassive Black Hole Binaries. We develop a model for supermassive black hole binaries (SMBHBs) accreting below their Eddington limit, focusing on systems where hot, advection-dominated flows become viable. We specifically explore the spectral appearance of multicomponent accretion flows where the solution can independently transition between cold, thin disks and hot, advection-dominated torii depending on the local accretion rate. Using a three-disk model, we compute spectral energy distributions for four possible accretion configurations and assess their observational signatures, including which frequencies might reflect variability at the binary orbital period. The spectral modeling reveals that binary accretion can self-consistently account for many of the properties of standard active galactic nuclei, while the variability analysis shows that hydrodynamic modulation at the binary period is most likely in the thermal emission and low-frequency synchrotron components. Doppler boosting of emitting material bound to a single binary component would also induce periodic variability. We apply our model to the SMBHB candidate PG1302-102 and demonstrate that a mixed-component accretion state (plus a jet feature) can self-consistently capture the observed broadband spectrum. Our model offers a framework for interpreting candidate SMBHBs and motivates future multiwavelength follow-up of potential multimessenger sources, as well as more detailed future modeling of multicomponent binary accretion.

Keywords: Accretion, Supermassive black holes, Low-luminosity active galactic nuclei, Active galactic nuclei
Electron Instabilities Driven by Beaming Electrons with Anisotropic Temperatures in High-beta Plasmas. Electron beams are ubiquitous in the heliosphere and dominate the electron heat flux. Large heat fluxes can excite microinstabilities, which are widely regarded as the primary mechanism regulating heat transport in the solar wind. Since electrons often exhibit temperature anisotropy, it is essential to clarify how anisotropy modifies beam-driven instabilities. Here we investigate the combined effects of electron streaming and temperature anisotropy on instability excitation. We find a general scenario: for slow-streaming beams, the parallel whistler heat flux instability transitions to an antiparallel whistler instability as anisotropy increases; for fast-streaming beams, the oblique whistler heat flux instability transitions to either an antiparallel whistler instability or an antiparallel left-hand Alfvén instability; and for superfast-streaming beams, the dominant mode is the electron beam/acoustic heat flux instability, which is largely insensitive to anisotropy. Furthermore, we identify a new whistler instability that arises from the interplay between streaming and temperature anisotropy.

Keywords: Space plasmas, Solar wind, Plasma physics
Thermonuclear X-Ray Bursts of 4U 0614+09: The Evidence for the Retreat of the Disk away from the Neutron Star. The thermonuclear X-ray burster, 4U 0614+09, which is located at a distance of ∼3 kpc, serves as a valuable laboratory for studying the interaction between thermonuclear X-ray bursts and the surrounding accretion environment. By analyzing the archived data from NICER and Insight-HXMT, we found that two bursts were identified by NICER, while none were detected by Insight-HXMT. Time-resolved spectroscopy of the bright burst revealed interaction-related characteristics, with the burst tail exhibiting an exceptionally prolonged duration exceeding 400 s—distinct from intermediate or superburst classifications—a feature discernible due to the source's relative proximity and enhanced instrumental sensitivity. There was a notable deviation from the expected canonical blackbody model near the burst peak, which could be attributed to either an enhanced preburst/persistent emission or the Comptonization of the burst and enhanced disk emission by the corona. The burst-induced flux enhancement of the accretion flow was observed to be proportional to the square root of the burst flux, i.e.,  LPR∝Lbb1/2 , which also suggests the retreat of the disk away from the neutron star. During the tail end of the X-ray burst cooling phase, the burst temperature stabilized at around 0.47 keV, with an inferred neutron star surface temperature of 0.33 keV. This temperature was used and fixed during the spectral fitting of the persistent/outburst emission.

Keywords: X-ray bursts
Bright Siren without an Electromagnetic Counterpart Detected by the LISA-Taiji-TianQin Network. Gravitational waves (GWs) with electromagnetic counterparts (EMc) offer a novel approach to measure the Hubble constant (H0), known as bright sirens, enabling H0 measurements by combining GW-derived distances with EM-derived redshifts. Host galaxy identification is essential for redshift determination but remains challenging due to poor GW sky localization and uncertainties in EMc models. To overcome these limitations, we exploit the ultrahigh-precision localization (∆Ωs ∼ 10−4 deg2) with a space-based GW detector network (LISA-Taiji-TianQin), which permits unique host identification solely from GW signals. We integrate five massive black hole binary (MBHB) population models and two galaxy number density models to compute the redshift horizon for host galaxy identification and evaluate H0 constraints. We find that (1) the network enhances localization by several orders of magnitude compared to single detectors; (2) the identification horizon reaches z ∼ 1.2 for specific MBHBs in the most accurate localization case; (3) the population model choice critically impacts the outcomes: the most refined population models yield to independent EMc identification rate of 0.6─1 yr−1 with H0 constraints &lt;1% fractional uncertainty, the less refined models lead to the rate &lt;0.1 yr−1 and 1%─2% uncertainty on H0.

Keywords: Gravitational wave astronomy, Supermassive black holes, Hubble constant, Cosmological parameters
Reconstructing PSP/ISOIS Pitch-angle-resolved Intensities Using Unsupervised Learning. The Integrated Science Investigation of the Sun (IS⊙IS) on board the Parker Solar Probe provides high-resolution measurements of energetic particles across a broad energy range. Of particular interest are the pitch-angle distributions (PADs), which offer insights into the directionality and transport of solar energetic particles (SEPs). However, 16% of the PAD data from the EPI-Lo instrument are systematically missing during SEP events owing to misalignment between the instrument's field of view and the local magnetic field direction. These data gaps cannot be reliably addressed using traditional interpolation methods, as PADs exhibit highly structured and nonlinear behavior. In this study, we develop and evaluate a suite of machine learning (ML) models—namely MICE, MISSForest, and M-RNN—to reconstruct missing PAD values across 28 SEP events observed between 2021 May and 2024 March. We find that MICE and a hybrid MICE─M-RNN model consistently outperform interpolation methods and other ML baselines. Approximately half of the SEP events yield high-confidence reconstructions, enabling the partial recovery of uninterrupted PADs and correction of artificial dropouts in omnidirectional intensity timelines. This type of PAD data loss is common across many heliophysics missions with fixed instrument fields of view; therefore, this study proves that ML imputation methods are a good candidate for improving PAD continuity in space-based observations across missions.

Keywords: Solar energetic particles
A Data-driven Approach for Star Formation Parameterization Using Symbolic Regression. Star formation (SF) in the interstellar medium (ISM) is fundamental to understanding galaxy evolution and planet formation. However, efforts to develop closed-form analytic expressions that link SF with key influencing physical variables, such as gas density and turbulence, remain challenging. In this work, we leverage recent advancements in machine learning (ML) and use symbolic regression (SR) techniques to produce the first data-driven, ML-discovered analytic expressions for SF using the publicly available FIRE-2 simulation suites. Employing a pipeline based on training the genetic algorithm of SR from an open software package called PYSR, in tandem with a custom loss function and a model selection technique that compares candidate equations to analytic approaches to describing SF, we produce symbolic representations of a predictive model for the star formation rate surface density (ΣSFR) averaged over both 10 Myr and 100 Myr based on eight extracted variables from FIRE-2 galaxies. The resulting model that PySR finds best describes SF, on both averaging timescales, features equations that incorporate the surface density of gas Σgas, the velocity dispersion of gas σgas,z, and the surface density of stars Σ*. Furthermore, we find that the equations found for the longer SFR timescale all converge to a scaling-relation-like equation, all of which also closely capture the intrinsic physical scatter of the data within the Kennicutt─Schmidt plane. This observed convergence to physically interpretable scaling relations at longer SFR timescales demonstrates that our method successfully identifies robust physical relationships rather than fitting to stochastic fluctuations.

Keywords: Interstellar medium, Star formation, Disk galaxies
Investigation for Binary Characteristics of LS I + 61°303 with Optical Polarization. We investigate the optical linear polarization caused by Thomson scattering of the stellar radiation for gamma-ray binary LS I + 61°303, which likely contains a young pulsar. Based on the pulsar binary scenario, we model the interaction between the pulsar wind and stellar wind from the massive companion star, which creates a shock. To accurately compute the resulting polarization of the stellar wind, we develop a method for the Thomson scattering that accounts for the finite size of the companion star. By fitting the optical polarization data, we constrain the system parameters, such as eccentricity, the momentum ratio of the two winds, and mass-loss rate from the companion star. We find that (i) the predicted eccentricity e ∼ 0.1 is smaller than the values derived from the radial velocity curve and (ii) the orbital phase of the periastron is νp = 0.5─0.6, which is consistent with the previous polarization study of Kravtsov et al. Additionally, we estimate the mass-loss rate from the companion star and the momentum ratio of two winds as  Ṁ∼2×10−6M⊙yr−1  and η &gt; 0.1, respectively. Assuming that the pulsar wind carries the spin-down energy, the spin-down magnetic field of the putative pulsar inferred from these parameters is of the order of B ∼ 1014 G, which may support the highly B pulsar or magnetar scenario for the compact object of LS I + 61°303. We also discuss the dispersion measure under the predicted orbital geometry and provide a corresponding interpretation of the pulsed radio signal detected by FAST.

Keywords: Shocks, Stellar winds, Binary stars, Starlight polarization