Sazuna/UAT_keywords huggingface dataset:
Worlds Next Door: A Candidate Giant Planet Imaged in the Habitable Zone of α Centauri A. II. Binary Star Modeling, Planet and Exozodi Search, and Sensitivity Analysis. The James Webb Space Telescope (JWST) observed our closest solar twin, α Centauri A (α Cen A), with the Mid-Infrared Instrument in the F1550C (15.5 μm) coronagraphic imaging mode at three distinct epochs between 2024 August and 2025 April. For the first time with JWST, we demonstrate the application of reference star differential imaging to simultaneously subtract the coronagraphic image of a primary star (α Cen A) and the point-spread function (PSF) of its binary companion (α Cen B) to conduct a deep search for exoplanets and exozodiacal dust emission. We achieve a typical 5σ point-source contrast sensitivity between ∼10‑5 and 10‑4 at separations ≳ 1″ and an exozodiacal disk (coplanar with α Cen AB) sensitivity of ∼5–8× the solar system's zodiacal cloud around α Cen A. The latter is an extraordinary limit, representing the deepest sensitivity to exozodiacal disks achieved for any stellar system to date. Additionally, postprocessing with the principal-component-analysis-based Karhunen–Loéve image processing algorithm reveals a point source, called S1, in 2024 August, detected at signal-to-noise ratio of 4–6 (3.3–4.3σ), a projected separation of ≈1 .″ 5 (2 au), and with an F1550C flux density (contrast) of ≈3.5 mJy (≈5.5 × 10‑5). Various tests conducted with the available data show that S1 is unlikely to be a detector artifact or PSF-subtraction artifact and confirm that it is neither a background nor a foreground object. S1 is not redetected in two follow-up observations (2025 February and April). If S1 is astrophysical in nature, the only explanation is that it has moved to a region of poor sensitivity due to orbital motion. We perform PSF injection–recovery tests and provide 2D sensitivity maps for each epoch to enable orbital completeness calculations. Additional observations, with JWST or upcoming facilities, are necessary to redetect candidate S1 and confirm its nature as a planet orbiting our nearest solar-type neighbor, α Cen A. More broadly, this program highlights the complexity of analyzing a dynamic binary astrophysical scene and the challenges associated with confirming short-period (∼few years) planet candidates identified without prior orbital constraints in direct imaging searches. This Letter is second in a series of two papers: Paper I discusses the observation strategy and presents the astrophysical case (physical and orbital properties) for S1 as a planet candidate.

Keywords: Coronagraphic imaging, James Webb Space Telescope, Extrasolar gaseous giant planets, Exozodiacal dust
A Flare-related Decimetric Type-IV Radio Burst Induced by the X2 Radiation of Electron Cyclotron Maser Emission. The radiation mechanism of decimetric wideband and pulsating radio bursts from the Sun (in terms of decimetric type-IV (t-IVdm) burst) and other flaring stars is a long-standing problem. Early investigations were based on the leading-spot hypothesis for the Sun and yielded contradictory results. Here, we analyzed the flare-associated t-IVdm burst on 20110924 with medium-strong levels of polarization and from sources near a sunspot. We found that the emission is intermittent and the maximum TB exceeds 1011 K, with well-defined upper and lower frequency cutoffs. The radio sources are left-handed polarized, located above the sunspot with a negative polarity. The sources align well with the sites of the second harmonic of the local electron gyrofrequency. These findings provide essential evidence that the burst is induced by the electron cyclotron maser emission (ECME) in the harmonic X mode. We further modeled the transport of downward-streaming energetic electrons along a coronal loop and found that most electrons get mirrored within the specific altitude range of 20–100 Mm. This explains why such bursts tend to have well-defined spectral ranges. We also found the ECME-radiating energetic electrons exhibit a shell-like velocity distribution function instead of the generally presumed loss-cone distribution. The study greatly expands the application of ECME in solar radio astronomy and provides solar samples for similar bursts from other flaring stars.

Keywords: Solar activity, Solar radio emission, Solar flares, Solar magnetic fields
Galactic Superaccreting X-Ray Binaries as Super-PeVatron Accelerators. The extension of the cosmic-ray (CR) spectrum well beyond 1 PeV necessitates the existence of a population of accelerators in the Milky Way, which we refer to as super-PeVatrons. Identifying the nature of these sources remains a challenge to the paradigm of Galactic CRs. Galactic superaccreting X-ray binaries (XRBs), where the compact object accretes at a rate near or above the Eddington limit, can meet the energy requirement to supply the high-energy population of Galactic CRs. We demonstrate that the transrelativistic jets and/or winds of these powerful objects with kinetic power exceeding 1039 erg s‑1 can accelerate protons to energies above several PeV. Detection of such superaccreting XRBs through their ultrahigh-energy gamma-ray "halos" and large-scale nebulae is also discussed.

Keywords: X-ray binary stars, High-energy cosmic radiation, Gamma-ray sources, Galactic cosmic rays, Ultraluminous x-ray sources, Cosmic ray sources
The Intermediate-mass Black Hole Reverberation Mapping Project: First Detection of Mid-infrared Lags in Prototypical Intermediate-mass Black Holes in NGC 4395 and POX 52. The search for robust evidence of intermediate-mass black holes (IMBHs) is crucial for understanding the black hole seeding process and the formation of supermassive black holes in the early Universe. NGC 4395 and POX 52 are two prototypical IMBH hosts, both exhibiting multiline evidence of low-mass black hole activity. Here we report the first detection of mid-infrared lags in response to optical variability, with measurements of  3.0−1.9+2.4  days for NGC 4395 and  35.2−11.7+14.2  days for POX 52 at 3.4 μm, respectively, using archival optical data and observations from the Wide-field Infrared Survey Explorer. This detection provides the first reverberation evidence of low-mass black hole activity in POX 52. The time lags of these two low-mass, low-luminosity active galactic nuclei (AGNs) generally follow the extent of the Rdust─L5100 relation found in higher-mass AGNs. Based on an empirical relation between the broad-line region and dusty torus size, we constrain the black hole mass of POX 52 to log(MBH/M⊙) = 5.5 ± 0.37 (systemic and statistical errors), confirming its IMBH nature. Furthermore, long-term optical continuum monitoring of POX 52 reveals a mild interband lag of ≲1 day. However, no significant intranight variability was detected during its one-night, high-cadence monitoring, which we attribute to the longer duty cycle of fast variability in POX 52 compared to that in NGC 4395.

Keywords: Intermediate-mass black holes
Possible Contamination of the Intergalactic Medium Damping Wing in ULAS J1342+0928 by Proximate Damped Lyα Absorption. The red damping wing from neutral hydrogen in the intergalactic medium is a key predicted signature of ongoing reionization. One potential contaminant of the intergalactic damping wing signal is dense gas associated with foreground galaxies, which can give rise to proximate damped Lyα absorbers. The Lyα imprint of such absorbers on background quasars is indistinguishable from the intergalactic medium within the uncertainty of the intrinsic quasar continuum, and their abundance at z ≳ 7 is unknown. Here we show that the complex of low-ionization metal absorption systems recently discovered by deep JWST/NIRSpec observations in the foreground of the z = 7.54 quasar ULAS J1342+0928 can potentially reproduce the quasar's spectral profile close to rest-frame Lyα without invoking a substantial contribution from the intergalactic medium, but only if the absorbing gas is extremely metal-poor ([O/H] ∼ ‑3.5). Such a low oxygen abundance has never been observed in a damped Lyα absorber at any redshift, but this possibility still complicates the interpretation of the spectrum. Our analysis highlights the need for deep spectroscopy of high-redshift quasars with JWST or the Extremely Large Telescope to "purify" damping wing quasar samples, an exercise that is impossible for much fainter objects like galaxies.

Keywords: Reionization, Damped Lyman-alpha systems, Quasar absorption line spectroscopy, Intergalactic medium
A Plasmoid Model for Mass Loss from Stars on the Upper Red Giant Branch: The Mass-loss Rate is Controlled by the Number of Density Scale Heights in the Convection Zone. Recent asteroseismic determinations of ΔM, the integrated mass loss on the red giant branch (RGB), for fields stars show a trend of ΔM decreasing as metallicity increases. This trend among field stars is inconsistent with many existing models of RGB mass loss. The present Letter is motivated by a "plasmoid" model of RGB mass loss in which magnetic flux loops, generated by a shear dynamo operating below the convection zone, are buoyed up to the stellar surface starting at the evolutionary stage right after the RGB "kink." This model leads us to examine correlations between, on the one hand, the average postkink RGB mass-loss rate, determined from ΔM and the postkink RGB lifetime, and on the other hand, stellar properties that exist just after the end of the kink. For three distinct stellar samples, we find strong anticorrelations between the average postkink RGB mass-loss rate and the number of density scale heights in the convection zone. This leads us to propose that the number of density scale heights in the convection zone is a dominant factor in determining the rate of the mass-loss process that sets in after the RGB kink.

Keywords: Magnetic stars, Red giant stars, Stellar mass loss
Impact of Magnetic-field-driven Anisotropies on the Equation of State Probed in Neutron Star Mergers. Binary neutron star mergers can produce extreme magnetic fields, some of which can lead to strong magnetar-like remnants. While strong magnetic fields have been shown to affect the dynamics of outflows and angular momentum transport in the remnant, they can also crucially alter the properties of nuclear matter probed in the merger. In this work, we provide a first assessment of the latter, determining the strength of the pressure anisotropy caused by Landau-level quantization and the anomalous magnetic moment. To this end, we perform the first numerical relativity simulation with a magnetic polarization tensor and a magnetic-field-dependent equation of state using a new algorithm we present here, which also incorporates a mean-field dynamo model to control the magnetic field strength present in the merger remnant. Our results show that—in the most optimistic case—corrections to the anisotropy can be in excess of 10% and are potentially largest in the outer layers of the remnant. This work paves the way for a systematic investigation of these effects.

Keywords: Neutron stars, Magnetohydrodynamics, Nuclear astrophysics, General relativity, Nuclear physics
Chandra Rules Out Super-Eddington Accretion Models for Little Red Dots. One of the most puzzling discoveries by JWST is the population of high-redshift, red, and compact galaxies dubbed little red dots (LRDs). Based on broad-line diagnostics, these galaxies have been argued to host accreting 107–108 M⊙ supermassive black holes (SMBHs), a claim with crucial consequences for our understanding of how the first black holes form and grow over cosmic time. A key feature of LRDs is their extreme X-ray weakness: analyses of individual and stacked sources have yielded nondetections or only tentative, inconclusive X-ray signals, except for a handful of individual cases. Although high obscuration is the most straightforward way to explain the X-ray weakness of LRDs, JWST rest-frame optical/UV spectra initially argued against the presence of Compton-thick gas clouds. Instead, several authors have proposed that LRDs are intrinsically X-ray weak due to super-Eddington accretion rates. In this work, we observationally test these tailored models by stacking X-ray data for 55 LRDs in the Chandra Deep Field South, accumulating a total exposure time of nearly 400 Ms. Despite reaching unprecedented X-ray depths, our stack still yields a nondetection. The corresponding upper limits are deep enough to rule out current super-Eddington accretion models and are compatible only with extremely high levels of obscuration (NH ≳ 1025 cm‑2). To explain the X-ray weakness of LRDs, we therefore speculate that the SMBHs in these systems are neither as massive nor as luminous as currently believed.

Keywords: Accretion, Supermassive black holes, James Webb Space Telescope, X-ray active galactic nuclei, Active galactic nuclei
Prediction of Time-evolving Radial Magnetic Fields on the Solar Surface Using Deep Learning. We develop two artificial intelligence–based models (Models A and B) to predict time-evolving photospheric magnetic fields with an adjustable time step, ranging up to one solar rotation later. Model A predicts future magnetic field data using three consecutive radial magnetic field data sets, each 12 hr apart. Model B reconstructs evolving magnetic fields using two sets of three consecutive data sets, one from a given date and the other from 27 days later, each 12 hr apart. To train and evaluate our models, we use a Pix2PixCC-based architecture and radial magnetic field data sets from the Solar Dynamics Observatory/Helioseismic and Magnetic Imager during the solar maximum periods of 2012–2016 and 2021–2023. Models A and B successfully generate magnetic field data corresponding to the input prediction time step. Based on quantitative comparison, Model A outperforms the persistence model and performs comparably to the classical surface flux transport model. Model B shows improved performance compared to both models. We also compare predictions for National Oceanic and Atmospheric Administration Active Regions 12673 and 13664, which rapidly emerged and produced powerful solar flares. Notably, both Models A and B can predict increases in total unsigned magnetic fluxes several days in advance if their evolution is already captured in the input data. Model B also reconstructs radial magnetic fluxes that smoothly overlap between the input data and the model outputs. These results demonstrate the ability of our models to generate time-evolving magnetic field data flexibly and capture emerging magnetic fluxes, which are crucial for heliophysics research and space weather forecasting.

Keywords: Solar magnetic flux emergence, The Sun, Convolutional neural networks, Astronomy data analysis, Solar magnetic fields
Metal-polluted Population III Galaxies and How to Find Them. Observing Population III (hereafter PopIII) galaxies, the hosts of first-generation stars, remains challenging even with the JWST. The current few candidates have been identified through the combination of a prominent He II emission and the absence of metal lines, a well-known but extremely brief signature of metal-free systems. Here, we accurately model the evolution of the emission from PopIII galaxies to increase the number of candidates in JWST observations. To achieve this, we employ a locally calibrated galaxy-formation model that self-consistently follows the star formation and chemical evolution initiated by the first stars. We find that PopIII galaxies can emit metal lines in their "self-polluted" phase, while galaxies host only metal-free stars, but the gas has been chemically enriched by the first supernovae. In this phase, PopIII galaxies have [O III]/Hβ ≈ 1, which opens the pool of candidates to more easily detectable sources. We predict that the high He II emission of PopIII galaxies can last up to ≈20 Myr and that it is partly maintained in the "hybrid" phase, when PopIII and Population II stars coexist in the host galaxy. We propose novel diagnostics involving ultraviolet metal lines to select PopIII candidates in high-z JWST surveys. In JADES, we identify nine candidate galaxies with &gt;25% of their stellar mass in metal-free stars, showcasing the effectiveness of our method. Ultimately, the key to discovering PopIII galaxies could be to catch them during their first episodes of chemical enrichment.

Keywords: Chemical enrichment, James Webb Space Telescope, Population III stars, High-redshift galaxies
JWST and Ground-based Observations of the Type Iax Supernovae SN 2024pxl and SN 2024vjm: Evidence for Weak Deflagration Explosions. We present panchromatic optical + near-infrared (NIR) + mid-infrared (MIR) observations of the intermediate-luminosity Type Iax supernova (SN Iax) 2024pxl and the extremely low-luminosity SN Iax 2024vjm. JWST observations provide unprecedented MIR spectroscopy of SN Iax, spanning from +11 to +42 day past maximum light. We detect forbidden emission lines in the MIR at these early times while the optical and NIR are dominated by permitted lines with an absorption component. Panchromatic spectra at early times can thus simultaneously show nebular and photospheric lines, probing both inner and outer layers of the ejecta. We identify spectral lines not seen before in SN Iax, including [Mg II] 4.76 μm, [Mg II] 9.71 μm, [Ne II] 12.81 μm, and isolated O I 2.76 μm that traces unburned material. Forbidden emission lines of all species are centrally peaked with similar kinematic distributions, indicating that the ejecta are well mixed in both SN 2024pxl and SN 2024vjm, a hallmark of pure deflagration explosion models. Radiative transfer modeling of SN 2024pxl shows good agreement with a weak deflagration of a near-Chandrasekhar-mass white dwarf, but additional IR flux is needed to match the observations, potentially attributable to a surviving remnant. Similarly, we find SN 2024vjm is also best explained by a weak deflagration model, despite the large difference in luminosity between the two supernovae. Future modeling should push to even weaker explosions and include the contribution of a bound remnant. Our observations demonstrate the diagnostic power of panchromatic spectroscopy for unveiling explosion physics in thermonuclear supernovae.

Keywords: White dwarf stars, Type Ia supernovae, Supernovae
A Direct Measurement of the Electron Density Turbulence Parameter C<SUB>1 </SUB>and Implications for the Emission Size of Magnetar XTE J1810-197. We report a direct measurement of the electron density turbulence parameter C1, enabled by 550–750 MHz baseband observations with the upgraded Giant Metrewave Radio Telescope. The parameter C1 depends on the power-law index of the wavenumber spectrum of electron density inhomogeneities in the ionized interstellar medium. Radio waves propagating through the inhomogeneous ionized medium suffer multipath propagation, as a result of which the pulsed emission from a neutron star undergoes scatter broadening. Consequently, interference between the delayed copies of the scatter-broadened electric field manifests as scintillation. We measure a scintillation bandwidth Δνd = 149 ± 3 Hz as well as a scatter-broadening timescale τd = 1.22 ± 0.09 ms at 650 MHz. These two quantities are related through the uncertainty relation C1 = 2πΔνdτd, using which we directly measure C1 = 1.2 ± 0.1. We describe the methods employed to obtain these results and discuss their implications in general, as well as for the magnetar XTE J1810‑197, toward which the measurements have been made. We also discuss how such effectively in situ measurements of C1 can aid in inferring the wavenumber spectrum power-law index and hence quantitatively discriminate between the various possible scattering scenarios in the ionized medium. Finally, using the fact that C1 ∼ 1, we nominally constrain the emission size to less than a few thousand kilometers for a screen very close to the magnetar and to within the magnetosphere for all screen distances.

Keywords: Interstellar scintillation, Interstellar medium, Radio transient sources
Discovery of a Pair of Galaxies with Both Hosting X-Ray Binary Candidates at z = 2.544. Among high-redshift galaxies, aside from active galactic nuclei (AGNs), X-ray binaries (XRBs) can be significant sources of X-ray emission. XRBs play a crucial role in galaxy evolution, reflecting the stellar populations of galaxies and regulating star formation through feedback, thereby shaping galaxy structure. In this study, we report a spectroscopically confirmed X-ray emitting galaxy pair (UDF3 and UDF3-2) at z = 2.544. By combining multiwavelength observations from JWST/NIRSpec Micro-Shutter Assembly spectra, JWST/NIRCam and MIRI imaging, Chandra, Hubble Space Telescope, Very Large Telescope, Atacama Large Millimeter/submillimeter Array, and Very Large Array, we analyze the ionized emission lines, which are primarily driven by H II region─like processes. Additionally, we find that the mid-infrared radiation can be fully attributed to dust emission from the galaxies themselves. Our results indicate that the X-ray emission from these two galaxies is dominated by high-mass XRBs, with luminosities of LX = (1.43 ± 0.40) × 1042 erg s−1 for UDF3 and (0.40 ± 0.12) × 1042 erg s−1 for UDF3-2. Furthermore, we measure the star formation rate (SFR) of  529−88+64  M⊙ yr−1 for UDF3, placing it ≍0.5 dex below the LX/SFR─z relation. This offset reflects the redshift-dependent enhancement of LX/SFR─z relation, which is influenced by metallicity and serves as a key observable for XRB evolution. In contrast, UDF3-2, with an SFR of  34−6+6  M⊙ yr−1, aligns well with the LX/SFR─z relation. This galaxy pair represents the highest redshift non-AGN-dominated galaxies with individual X-ray detections reported to date. This finding suggests that the contribution of XRBs to galaxy X-ray emission at high redshift may be underestimated.

Keywords: High mass x-ray binary stars, Metallicity, X-ray binary stars, High-redshift galaxies
Discovery and Preliminary Characterization of a Third Interstellar Object: 3I/ATLAS. We report initial observations aimed at the characterization of a third interstellar object. This object, 3I/ATLAS or C/2025 N1 (ATLAS), was discovered on 2025 July 1 UT and has an orbital eccentricity of e ∼ 6.1, perihelion of q ∼ 1.36 au, inclination of ∼175°, and hyperbolic velocity of V∞ ∼ 58 km s−1. We report deep stacked images obtained using the Canada─France─Hawaii Telescope and the Very Large Telescope that resolve a compact coma. Using images obtained from several smaller ground-based telescopes, we find minimal light-curve variation for the object over a ∼4 day time span. The visible/near-infrared spectral slope of the object is 17.1% ± 0.2%/100 nm, comparable to other interstellar objects and primitive solar system small bodies (comets and D-type asteroids). Moreover, 3I/ATLAS will be observable through early 2025 September, then unobservable by Earth-based observatories near perihelion due to low solar elongation. It will be observable again from the ground in late 2025 November. Although this limitation unfortunately prohibits detailed Earth-based observations at perihelion when the activity of 3I/ATLAS is likely to peak, spacecraft at Mars could be used to make valuable observations at this time.

Keywords: Meteors, Comets, Asteroids, Interstellar objects