Sazuna/UAT_keywords huggingface dataset:
Distinct Fe K Line Complexes in MAXI J1744−294 Revealed by XRISM High-resolution Spectroscopy. The newly discovered Galactic transient MAXI J1744−294 went into its first X-ray outburst in 2025. We study the spectral properties of this source in the 2─10 keV energy band during this outburst using X-ray data from the XRISM satellite for both of its Resolve and Xtend instruments, taken on 2025 March 3. High-resolution spectroscopy has revealed, for the first time, complex iron line features in this source, corresponding to distinct components of Fe XXV emission and Fe XXVI absorption lines. Such a detailed structure has not been reported in other low-mass X-ray binaries to date, prior to the XRISM era. Our analysis shows that the line complexes arise from two highly ionized plasmas with an ionization rate ∼103 erg cm s−1 with distinct turbulent velocities—one broad (vturb ≍ 2513 km s−1) from hot gas at the inner accretion disk and one narrow (vturb ≍ 153 km s−1) scattered by nearby photoionized gas. These results offer new insight into the reprocessing of continuum in stratified media, either in the accretion disk or winds, or both, for X-ray binaries in the soft state. The data are well described by models with spin, mass of the black hole, and accretion disk inclination 0.63─0.70, 7.9 ± 2.2 M⊙, and 19°─24°. The fitted spectral model parameters suggest that the source is in the soft spectral state. The source is situated in a crowded field near the Galactic center, resulting in a large hydrogen column density.

Keywords: Stellar accretion disks, X-ray binary stars, Black holes, Compact radiation sources
Revisiting the Supermassive Black Hole Mass of NGC 7052 Using High Spatial Resolution Molecular Gas Observed with ALMA. We present our dynamical mass constraints on the central supermassive black hole (SMBH) in the early-type galaxy NGC 7052 using high spatial-resolution observations of 12CO(2─1) emission from the Atacama Large Millimeter/submillimeter Array (ALMA). The data were obtained during ALMA Cycle 7 and have a synthesized beam size of 0 .″ 29 ×0 .″ 22 (97 × 73 pc2). The dynamical model yielded an SMBH mass of ≍(2.50 ±0.37 [statistical] ± 0.8 [systematic]) × 109 M⊙ and a stellar I-band mass-to-light ratio of ≍4.08 ±0.23 [statistical] ± 0.4 [systematic] M⊙/L⊙,I (3σ confidence intervals). Although our new ALMA observation has three times lower spatial resolution than previous ALMA data, it still resolves the SMBH's sphere of influence with a spatial resolution that is 1.5 times smaller than this sphere radius. While our MBH estimate is fully consistent with the previous determination, the I-band mass-to-light ratio is lower by 10%. This difference arises from our improved galaxy mass model, which incorporates both the molecular gas distribution and the extended stellar mass in the outer regions of the galaxy, the components that were previously neglected.

Keywords: Astronomy data modeling, Galaxy dynamics, Galaxy kinematics, Interstellar medium, Radio interferometry, Astrophysical black holes
JADES-GS-z14-1: A Compact, Faint Galaxy at z ≈ 14 with Weak Metal Lines from Extremely Deep JWST MIRI, NIRCam, and NIRSpec Observations. JWST has shed light on galaxy formation and metal enrichment within 300 Myr of the Big Bang. While luminous galaxies at z &gt; 10 often show significant [O III] λλ4959, 5007 emission lines, it remains unclear whether such features are prevalent among fainter, more typical galaxies due to observational limits. We present deep imaging and spectroscopy of JADES-GS-z14-1 at  zspec=13.86−0.05+0.04 , currently the faintest spectroscopically confirmed galaxy at z ≈ 14. It serendipitously received 70.7 hr of MIRI/F770W imaging in the JWST Advanced Deep Extragalactic Survey (JADES), the deepest MIRI exposure for any high-redshift galaxy to date. Nonetheless, we detect only tentative F770W emission of 7.9 ± 2.8 nJy at 2.8σ significance, constraining the total equivalent width of [O III] λλ4959, 5007 + Hβ to  520−380+400  Å, weaker than most z &gt; 10 galaxies with MIRI detections. This source is unresolved across 16 NIRCam bands, implying a physical radius ≲50 pc. NIRSpec/PRISM spectroscopy totaling 56 hr reveals no rest-frame ultraviolet emission lines above 3σ. Stellar population synthesis suggests a stellar mass ∼4 × 107 M⊙ and a star formation rate ∼2 M⊙ yr−1. The absence of strong metal emission lines despite intense star formation suggests a gas-phase metallicity below 10% solar and potentially a high escape fraction of ionizing photons. These deep observations provide rare constraints on faint, early galaxies, tracing the onset of chemical enrichment and ionization in the early Universe.

Keywords: Galaxy formation, High-redshift galaxies, Galaxy evolution
Structure and Dynamics of the Young Massive Star Cluster Westerlund 1. We present a structural and dynamical analysis of the young massive star cluster Westerlund 1 (Wd1). Using multiepoch Hubble Space Telescope observations, we measure the proper motions of 10,346 stars and present an unprecedented determination of cluster membership probability. We then determine the color membership after correcting for extinction. The stellar density map weighted by the membership probability and completeness correction displays a spatial elongation aligned with the Galactic plane with a high eccentricity of 0.71. The radial stellar density profile shows a decreasing core radius with increasing mass, indicative of weak but detectable mass segregation. Quantitatively, the measured mass segregation ratio is ΛMSR = 1.11 ± 0.11, only above unity by 1σ. Building on the structural modeling along with a suite of stellar evolutionary and atmospheric models, we fit the cluster age and distance in two color─magnitude diagrams, concluding that Wd1 is approximately 7.45 ± 0.53 Myr old and at a distance of 3.7 ± 0.1 kpc, with a degeneracy in the posterior which is compatible with the literature values. We measure a 1D velocity dispersion of 4.13 ± 0.13 km s−1, indicating a subvirialized state. The crossing time is 0.30 Myr and the relaxation time is 0.26 Gyr. Given the age of Wd1, we expect dynamical mass segregation for stars more massive than 12 M⊙, which accounts for the minor mass segregation observed in the mass range of 1.12─15.21 M⊙ in this work. This suggests that the mass segregation in Wd1 is more likely a dynamical effect.

Keywords: Stellar kinematics, Star forming regions, Star formation, Star clusters
Mitigating Eddington and Malmquist Biases in Latent-inclination Inference of the Tully─Fisher Relation. The Tully─Fisher relation is a vital distance indicator, but its precise inference is challenged by selection bias, statistical bias, and uncertain inclination corrections. This study presents a Bayesian framework that simultaneously addresses these issues. To eliminate the need for individual inclination corrections, inclination is treated as a latent variable with a known probability distribution. To correct for the distance-dependent Malmqvist bias arising from sample selection, the model incorporates Gaussian scatter in the dependent variable, the distribution of the independent variable, and the observational selection function into the data likelihood. To mitigate the statistical bias, termed the "general Eddington bias," caused by Gaussian scatter and the nonuniform distribution of the independent variable, two methods are introduced: (1) analytical bias corrections applied to the dependent variable before likelihood computation, and (2) a dual-scatter model that accounts for Gaussian scatter in the independent variable within the likelihood function. The effectiveness of these methods is demonstrated using simulated data sets. By rigorously addressing selection and statistical biases in a latent-variable regression analysis, this work provides a robust approach for unbiased distance estimates from standardizable candles, which is critical for improving the accuracy of Hubble constant determinations.

Keywords: Bayesian statistics, Disk galaxies, Scaling relations, Linear regression, Maximum likelihood estimation
Potassium Abundances in Extremely Metal Poor Stars: Implications for Nucleosynthesis in the Final Stages of Massive Star Evolution. We present a potassium (K) abundance analysis in extremely metal-poor (EMP) stars based on high-resolution (R ∼ 60,000) spectra obtained with the High Dispersion Spectrograph on the Subaru Telescope, covering the K I resonance lines at 766 and 769 nm. One-dimensional local thermodynamic equilibrium (LTE) abundances of K and other elements, including Na, Mg, Ca, Ti, Cr, and Ni, were derived using spectral synthesis. Non-LTE (NLTE) corrections were applied to the K abundances by interpolating a precomputed grid of corrections based on stellar parameters and the LTE K abundance. We detected K I lines in seven stars with [Fe/H] &lt; ─3.0 and derived upper limits for other stars in the same metallicity regime, making this sample well-suited for investigating the nucleosynthesis origins of K in the early Universe. We found that the [K/Fe] and [K/Ca] ratios of the seven stars are enhanced relative to the solar value, with a scatter of ∼0.1 dex, as small as the typical measurement uncertainty. Under the assumption that each star formed from gas purely enriched by a single or a few massive star's supernova, the small scatter in [K/Fe] and [K/Ca], contrasted with the ∼0.7 dex scatter in [Na/Mg] ratios (after NLTE correction), suggests that the production of K in massive stars or their supernovae is independent of the processes that drive the Na/Mg variation. These findings demonstrate that K abundances in EMP stars, and their correlations with other elemental abundances, can serve as sensitive tracers of the physical mechanisms governing the final evolutionary stages of massive stars and their supernova explosions. ∗This research is based on data collected at the Subaru Telescope, which is operated by the National Astronomical Observatory of Japan. We are honored and grateful for the opportunity of observing the Universe from Maunakea, which has cultural, historical, and natural significance in Hawaii.

Keywords: Late stellar evolution, Galactic archaeology, Core-collapse supernovae, Nucleosynthesis
Cool Dark Gas in Cygnus X: The First Large-scale Mapping of Low-frequency Carbon Recombination Lines. Understanding the transition from atomic gas to molecular gas is critical to explain the formation and evolution of molecular clouds. However, the gas phases involved, cold H I and CO-dark molecular gas, are challenging to directly observe and physically characterize. We observed the Cygnus X star-forming complex in carbon radio recombination lines (CRRLs) at 274─399 MHz with the Green Bank Telescope at 48 '  (21 pc) resolution. Of the 30 deg2 surveyed, we detect line-synthesized C273α emission from 24 deg2 and produce the first large-area maps of low-frequency CRRLs, which likely originate in CO-dark molecular gas. The morphology of the C273α emission reveals arcs, ridges, and extended possibly sheet-like gas, which are often found on the outskirts of CO emission. We find a correlation between velocity-integrated C273α and the 8 μm intensity with a power-law slope of 1.3 ± 0.2. We interpret the relation as the dependence of cool dark gas emission on the far-ultraviolet radiation field, G0 ≍ 40−160. We determine the typical angular separation between C273α and 13CO emission to be 12 pc. Velocity differences between C273α and 13CO are apparent throughout the region and have a typical value of 2.9 km s−1. We estimate gas densities of n ≍ 20−900 cm−3 with a nominal n ≍ 400 cm−3 in the C+/H2 layer. The evolution of the C273α gas seems to be dominated by turbulent pressure, with a characteristic timescale to form H2 of about 2.6 Myr. These observations underline the richness of low-frequency CRRLs to provide revelatory insights into the characteristics of (CO-)dark gas and the evolution of molecular gas.

Keywords: Radio spectroscopy, Interstellar atomic gas, Interstellar clouds, Interstellar medium, Milky Way Galaxy
Observations of a Faint Nonthermal Onset before a GOES C-class Flare. We present an analysis of a GOES C1-class flare from 2022 September 6, which was jointly observed as occulted by Nuclear Spectroscopic Telescope ARray (NuSTAR) and on-disk by Spectrometer/Telescope for Imaging X-rays (STIX). NuSTAR observed faint coronal nonthermal emission as well as plasma heating &gt;10 MK, starting 7 minutes prior to the flare. This onset emission implies that during this time, there is a continuous electron acceleration in the corona, which could also be responsible for the observed heating. The nonthermal model parameters remained consistent throughout the entire onset, indicating that the electron acceleration process persisted during this time. Furthermore, the onset coincided with a series of type III radio bursts observed by Long Wavelength Array-1, further supporting the presence of electron acceleration before the flare began. We also performed spectral analysis of the impulsive flare emission with STIX (thermal and footpoint emission). STIX footpoints and the onset coronal source were found to have similar electron distribution power-law indices, but with increased low-energy cut-off during the flare time. This could suggest that the nonthermal onset is an early signature of the acceleration mechanism that occurs during the main phase of the flare.

Keywords: Solar atmosphere, Solar flares, Active sun, Solar x-ray emission, Solar corona
Discovery of an Accretion Burst in a Free-floating Planetary-mass Object. We report the discovery of a long-lasting burst of disk accretion in Cha J11070768-7626326 (Cha 1107-7626), a young, isolated, 5─10 MJupiter object. In spectra taken with XSHOOTER at ESO's Very Large Telescope as well as NIRSpec and MIRI on the James Webb Space Telescope, the object transitions from quiescence in 2025 April─May to a strongly enhanced accretion phase in 2025 June─August. The line flux changes correspond to a 6─8-fold increase in the mass accretion rate, reaching 10−7 MJupiteryr−1, the highest measured in a planetary-mass object. During the burst, the Hα line develops a double-peaked profile with redshifted absorption, as observed in stars and brown dwarfs undergoing magnetospheric accretion. The optical continuum increases by a factor of 3─6; the object is ∼1.5─2 mag brighter in the R band during the burst. Mid-infrared continuum fluxes rise by 10%─20%, with clear changes in the hydrocarbon emission lines from the disk. We detect water vapour emission at 6.5─7 μm, which were absent in quiescence. By the end of our observing campaign, the burst was still ongoing, implying a duration of at least 2 months. A 2016 spectrum also shows high accretion levels, suggesting that this object may undergo recurring bursts. The observed event is inconsistent with typical variability in accreting young stars and instead matches the duration, amplitude, and line spectrum of an EXor-type burst, making Cha1107-7626 the first substellar object with evidence of a potentially recurring EXor burst.

Keywords: Brown dwarfs, Infrared spectroscopy, H I line emission, Young stellar objects, Protoplanetary disks, Spectroscopy, Stellar accretion disks
The Landscape of Collapsar Outflows: Structure, Signatures, and Origins of Einstein Probe Relativistic Supernova Transients. The Einstein Probe is revolutionizing time-domain astrophysics through the discovery of new classes of X-ray transients associated with broad-line Type Ic supernovae. These events commonly exhibit bright early-time optical counterparts and sudden afterglow rebrightening within the first week—features that existing models fail to explain. In particular, structured jet and cocoon scenarios are inconsistent with the observed sharp rebrightening and multiday optical emission, while the refreshed shock model is ruled out owing to its inconsistency with collapsar hydrodynamics. Drawing on 3D general relativistic magnetohydrodynamic simulations, we present the multiscale angular and radial structure characterizing collapsar outflows. The resulting morphology features episodic, wobbling jets with a "top-hat" geometry, embedded within a smoother global cocoon and disk ejecta angular structure. The wobbling jets give rise to variations in radiative efficiency that can account for the observed alternation between X-ray-dominated and γ-ray-dominated jet emission. The top-hat structure of individual wobbling jet episodes naturally explains the sudden rebrightening observed when the emission from the top-hat jet cores enters the observer's line of sight. The radial structure is consistent with that inferred from observations of stripped-envelope supernovae. It comprises a mildly relativistic cocoon (0.3 ≲ βΓ ≲ 3) that may power an early (∼1 day) rapidly decaying emission, followed by slower, black-hole-accretion-disk-driven outflows (β ≲ 0.3), which dominate the slowly evolving optical emission at t ≳ 1 day. This novel multicomponent outflow structure provides a unified explanation for the multiband light curves observed in Einstein Probe transients and is likely a common feature of broad-line Type Ic supernovae more broadly.

Keywords: Gamma-ray bursts, Jets, Core-collapse supernovae, Transient sources, X-ray transient sources, Gamma-ray transient sources
Magnetic Turbulence Intermittency and Compressibility in the Inner Heliosheath and Very Local Interstellar Medium. We analyze Voyager 1 magnetic field data through 2024 to study fluctuations from the inner heliosheath into the very local interstellar medium (VLISM). We focus on inertial-range intermittency and magnetic compressibility and examine the effects of interstellar shocks and pressure fronts. The heliosheath shows consistently high fluctuation amplitude (δB/B0 ∼ 1) and compressibility, indicating the presence of compressive wave modes. The elevated sound speed from pickup ion pressure inhibits wave steepening within the heliosheath, but steepening may occur near or just beyond the heliopause, enabling partial transmission into the VLISM. Beyond the heliopause, magnetic compressibility decreases following the second pressure front at ∼149 au. Intermittency, measured via scale-dependent flatness, also decreases with distance but shows localized enhancements near pressure fronts and shocks in the VLISM. A pronounced peak in flatness at time lags around 105 s is observed downstream of the second pressure front, primarily in the parallel magnetic field component, indicating large-scale compressive structures. In contrast, the peak flatness downstream of the first pressure front (at ∼137 au) occurs at shorter time lags, likely due to differences in plasma conditions, structure scales, or elevated noise in the deeper VLISM. An overall decrease in intermittency, approaching near-Gaussian levels, is observed after the second pressure front. However, weak intermittency still persists at small time lags over the past 2 yr, indicating that intermittency does not fully vanish after the magnetic hump.

Keywords: Interstellar medium, Interplanetary magnetic fields, Solar wind termination
Numerical Simulations Confirm Wave-induced Shear Mixing in Stellar Interiors. Internal gravity waves (IGWs) are thought to cause mixing in stellar interiors, a process that has been widely studied both theoretically and numerically. Our aim is to determine the physical mechanism responsible for the wave-induced mixing in stellar interiors. We compare the mixing profiles obtained from two-dimensional (2D) equatorial hydrodynamical and tracer particle simulations with theoretical predictions from R. J. Garcia Lopez &amp; H. C. Spruit and J. P. Zahn (1992) on wave mixing due to wave-induced shear turbulence. Our results show that, despite not satisfying the vertical shear instability threshold, the mixing profiles from the simulations agree remarkably well with the theoretical predictions of both prescriptions, strongly suggesting that shear from IGWs plays an important role in mixing even at low shear rates. This agreement remains robust across different stellar masses, ages, rotation and simulation parameters. This provides an important step in providing realistic parameterisations for wave mixing in stellar structure and evolution models.

Keywords: Hydrodynamical simulations, Internal waves, Stellar evolution
Absence of Radio Emission Reveals an Exceptionally Weak Explosion of the Putative Historical Supernova Pa 30. We present the first deep radio continuum observations of Pa 30, a nebula hosting a unique optical source driven by an ultrafast outflow with a velocity of 16,000 km s−1. The nebula was proposed to be the remnant of a white dwarf merger that occurred in 1181CE. We report no detection of the radio diffuse emission from Pa 30 or radio emission from the central source, setting 3σ upper limit flux densities of 0.84 and 0.29 mJy at 1.5 and 6 GHz, respectively, for Pa 30. The radio surface brightness of Pa 30 is ∼3 orders of magnitude smaller than that of typical supernova remnants (SNRs) with comparable angular size. If Pa 30 is an SNR, our observations show it to be the faintest known in the radio band. Considering that 10% of the supernova (SN) kinetic energy is transferred to cosmic rays (CRs), the absence of radio synchrotron emission suggests that the SN kinetic energy ≲3 × 1047(B/10 μG)−1.65 erg, which is 3─4 orders of magnitude lower than that of typical SNRs and the lowest measured among Galactic SNRs. There is also an indication of inefficient CR acceleration for this source. The low SN kinetic energy either implies the potential existence of many more radio-faint, subenergetic SNRs in our Galaxy or challenges the SNR interpretation of Pa 30.

Keywords: Stellar mergers, White dwarf stars, Supernova remnants, Type Ia supernovae, Cosmic rays
Characterization of Two Cool Galaxy Outflow Candidates Using Mid-infrared Emission from Polycyclic Aromatic Hydrocarbons. We characterize two candidate cool galactic outflows in two relatively low-mass, highly inclined Virgo cluster galaxies: NGC 4424 and NGC 4694. Previous analyses of observations using the Atacama Large Millimeter/submillimeter Array carbon monoxide (CO) line emission maps did not classify these sources as cool outflow hosts. Using new high-sensitivity, high-spatial-resolution, JWST mid-infrared photometry in the polycyclic aromatic hydrocarbon (PAH)─tracing F770W band, we identify extended structures present off of the stellar disk. The identified structures are bright in the MIRI F770W and F2100W bands, suggesting they include PAHs as well as other dust grains. As PAHs have been shown to be destroyed in hot, ionized gas, these structures are likely to be outflows of cool (T ≤ 104 K) gas. This work represents an exciting possibility for using mid-infrared observations to identify and measure outflows in lower-mass, lower star formation galaxies.

Keywords: Galaxies, Infrared photometry, Polycyclic aromatic hydrocarbons, Interstellar medium
Electromagnetic Energy Extraction from Kerr Black Holes: Ab Initio Calculations. The possibility of extracting energy from a rotating black hole via the Blandford–Znajek mechanism represents a cornerstone of relativistic astrophysics. We present general-relativistic collisionless kinetic simulations of Kerr black hole magnetospheres covering a wide range of black hole spin rates. Considering a classical split-monopole magnetic field, we can reproduce with these ab initio calculations the force-free electrodynamics of rotating black holes and measure the power of the jet launched as a function of the spin. The Blandford–Znajek luminosity we find is in very good agreement with analytic calculations and compatible with general-relativistic magnetohydrodynamic simulations via a simple rescaling. These results provide strong evidence of the robustness of the Blandford–Znajek mechanism and accurate estimates of the electromagnetic luminosity to be expected in those scenarios involving rotating black holes across the mass scale.

Keywords: Space plasmas, General relativity, High energy astrophysics