Sazuna/UAT_keywords huggingface dataset:
Discovery of Thermal Rossby Waves and Evidence for Weak Large-scale Convection in the Solar Interior. Compressible Rossby waves—long predicted by theories of rotating stratified convection—offer a unique window into the dynamical structure of the solar interior. Despite their foundational status in astrophysical convection theory, they have evaded unambiguous detection for more than half a century. Analyzing nearly 15 yr of space- and ground-based helioseismic observations using normal-mode coupling, we report the discovery of a coherent, dispersive family of prograde inertial vorticity waves confined to depths below r/R⊙ &lt; 0.98, with amplitudes &lt;10 cm s−1, at spatial harmonic degrees ranging up to s ∼ 75, and oscillating at temporal frequencies comparable to the solar rotation rate. Convection drives fluid flows, which, in the parameter regime that applies to the Sun, are likely turbulent. We argue that our measurements hint at convective extinction below r/R⊙ ∼ 0.98, thereby marking a transition from vigorous surface turbulence to rotationally constrained (Rossby number ∼10−4─10−3), weakly turbulent (&lt;3 m s−1) dynamics.

Keywords: Solar convective zone
Energy Partition in Collisionless Counterstreaming Plasmas. Fast, counterstreaming plasma outflows drive magnetic field amplification, plasma heating, and particle acceleration in numerous astrophysical environments, from supernova remnant shocks to active galactic nuclei jets. Understanding how, in the absence of Coulomb collisions, energy is redistributed between the different plasma species remains a fundamental open question. We use three-dimensional, fully kinetic simulations to investigate energy partition in weakly magnetized counterpropagating plasmas. Our results reveal a complex interplay between different processes, where at early times the Weibel instability drives a first stage of magnetic field amplification and at late times the kinking of current filaments drives a second amplification stage via a dynamo-type mechanism. Electrons are heated primarily during the latter phase through magnetic pumping. By the time the flows thermalize, we observe that the final temperature ratio Te/Ti and energy partition depend on the ion-to-electron mass ratio. For electron─proton flows, the electron thermal energy only reaches up to a few percent of the initial ion kinetic energy.

Keywords: Shocks, Plasma astrophysics, High energy astrophysics
Discovery of an Extremely Luminous Type II Cepheid in the Andromeda Giant Stellar Stream: Evidence for a Hierarchical Triple with an Inner Binary Merger. We report the discovery of LAMOST J0041+3948, the most luminous post-asymptotic giant-branch (AGB) Type II Cepheid known, located in the Andromeda Giant Stellar Stream. Its spectral energy distribution (SED) exhibits a strong near-infrared excess, indicating the presence of a circumbinary dusty disk and hence binarity. SED fitting yields an effective temperature of  Teff=6738−262+234  K and a post-AGB luminosity of  log(L/L⊙)=4.32−0.08+0.07 . Comparison with theoretical evolutionary tracks suggests a ∼2.0─4.0 M⊙ progenitor when accounting for a possible scattered-light contribution. Zwicky Transient Facility light curves reveal a pulsation period of 89 days that lies close to the period─luminosity relation for long-period RV Tauri stars. Follow-up spectroscopy reveals clear s-process enrichment and signatures consistent with an accretion disk around the companion. The inferred progenitor is significantly younger and more massive than a typical stream member, suggesting that an additional mechanism, such as a stellar merger, is required. We propose a formation channel in which the present post-AGB binary descends from a hierarchical triple system. In this scenario, the inner binary merged after the system was displaced to its current location by the galaxy merger event, and the resulting massive merger remnant subsequently evolved into the extremely luminous post-AGB star observed today.

Keywords: Binary stars, Post-asymptotic giant branch stars, Late stellar evolution, Multiple star evolution, Stellar luminosities, Circumstellar disks, Type II Cepheid variable stars, RV Tauri variable stars, Andromeda Galaxy
Detection of Oscillations in a Type I X-Ray Burst of 4U 0614+091 with SVOM/ECLAIRs. On 2025 January 10, a thermonuclear (Type I) X-ray burst from the neutron star low-mass X-ray binary (LMXB) 4U 0614+091 was detected with the ECLAIRs instrument on board the Space-based multiband astronomical Variable Object Monitor mission. We present here a time-resolved spectroscopic analysis of the burst, along with the detection of burst oscillations within a 51 s interval during the decay phase. The oscillation frequency is measured to be ν = 413.674 ± 0.002 Hz, consistent with previous reports. However, we detect a significant downward frequency drift over the burst duration, characterized by  ν̇=(−4.7±0.3)×10−3Hzs−1 . This frequency evolution is atypical compared to those observed in similar burst oscillation sources. We tentatively attribute the observed drift to a Doppler shift induced by orbital motion. Under this interpretation, the inferred orbital period must be shorter than 20 minutes, placing 4U 0614+091 among the most compact known LMXBs.

Keywords: Low-mass x-ray binary stars, Compact binary stars, X-ray bursts
XRISM Finds the Changing-look Active Galactic Nucleus NGC 1365 in an Extended Low State: A Dense, Highly Ionized Outflow Obscures the Central Source. We present the first XRISM/Resolve observations of the active galactic nucleus NGC 1365, obtained in 2024 February and July. NGC 1365 is known for rapid transitions between Compton-thick and Compton-thin states, along with strong absorption from a highly ionized wind. During our observations, the source was found in a persistent low-flux state, characterized by a decrease in hard-X-ray luminosity and significant line-of-sight obscuration. In this state, XRISM/Resolve reveals clear Fe xxv and Fe XXVI absorption lines together with, for the first time in this source, corresponding emission lines. These features may arise either from reemission from a photoionized wind (P Cygni profile) or from collisionally ionized gas associated with outflow-driven shocks in the interstellar medium. We estimate the wind launch radius to be approximately 1016 cm (∼104Rg), consistent with the location of the X-ray broadline region. We also resolve a broadened Fe Kα line by σ ∼ 1300 km s−1, placing it at similar scales to the wind, consistent with radii inferred from disk-broadening models and the variability of the Fe Kα broad line. The similarity of the Fe Kα profile to the Hβ wing and broad Paα width indicates that the X-ray-emitting region is likely cospatial with the optical/infrared broadline region and originates from the same gas.

Keywords: X-ray astronomy, High resolution spectroscopy, High energy astrophysics, Seyfert galaxies, X-ray active galactic nuclei, Active galactic nuclei, Astrophysical black holes
Probing the Large-scale Magnetic Field inside the Sun from Three Decades of Observed Surface Magnetograms. Space weather and disturbances in the heliosphere are manifestations of the solar magnetic field, which is solely driven by the interior dynamo. Constraining the solar interior magnetic field and its oscillatory behavior is one of the major challenges in solar physics. Observationally, none of the techniques—including helioseismology—are able to provide an estimation of the interior magnetic field. We reconstruct, for the first time, the dynamics of the interior large-scale magnetic fields, by assimilating observed line-of-sight photospheric magnetogram data from the Michelson Doppler Imager/Solar and Heliospheric Observatory and the Helioseismic and Magnetic Imager/Solar Dynamics Observatory, along with helioseismic differential rotation data over three decades (1996─2025), into a 3D Babcock─Leighton dynamo model. The assimilation of the observational magnetogram data allows for realistic modeling of the Babcock─Leighton mechanism as observed on the Sun without any simplified parameterization. As a result, our data-driven model successfully reproduces key observational features, such as the surface butterfly diagram, accurate polar field evolution, and axial dipole moment. The reconstructed interior field dominated by the toroidal component exhibits an equatorward migration and reproduces realistic amplitudes and modulations of Cycles 23─25. We observe that the nonaxisymmetric behavior of the interior toroidal field becomes less prominent as we move deep toward the tachocline, according to our model. A strong correlation between the simulated toroidal field and sunspot number establishes our 3D magnetogram-driven model as a robust predictive model of the solar cycle.

Keywords: Solar cycle, Solar differential rotation, Solar interior, Sunspots, Solar dynamo, Solar physics, Magnetogram
Observation of Large-scale Kelvin─Helmholtz Instability Wave Driven by a Coronal Mass Ejection. The Kelvin─Helmholtz instability (KHI) can occur when there is a relative motion between two adjacent fluids. In the case of magnetized plasma, the shear velocity must exceed the local Alfvén speed for the instability to develop. The KHI produces nonlinear waves that eventually roll up into vortices and contribute to turbulence and dissipation. In the solar atmosphere, KHI has been detected in coronal mass ejections (CMEs), jets, and prominences, mainly in the low corona. Only a few studies have reported the KHI in the upper corona, and its vortex development there has not been previously observed. We report an event with large-scale KHI waves observed from ∼6 to 14 R⊙ on 2024 February 16 using Solar and Heliospheric Observatory/Large Angle and Spectrometric Coronagraph and STEREO-A coronagraphs. A KHI appeared during the passage of a fast CME and evolved into the nonlinear stage showing evidence of vortices. A closely timed subsequent CME in the same region further developed the fully nonlinear KHI waves along its flank. We find that the radial speed of the CMEs exceeds the estimated local Alfvén speed obtained from in-situ Parker Solar Probe magnetic field data at perihelia. We propose that such events are rare because the fast CME created specific conditions favorable for instability growth in its trailing edge, including radial elongation of magnetic-field lines, reduced plasma density, and enhanced velocity and magnetic-field shear along the developing interface. The observed growth rate of the KHI wave is in qualitative agreement with the theoretical predictions.

Keywords: Active solar corona, Solar coronal waves, Solar coronal mass ejections
Soot Planets Instead of Water Worlds. Some low-density exoplanets are thought to be water-rich worlds that formed beyond the snow line of their protoplanetary disk, possibly accreting coequal portions of rock and water. However, the compositions of bodies within the solar system and the stability of volatile-rich solids in accretionary disks suggest that a planet rich in water should also acquire as much as 40% refractory organic carbon ("soot"). This would reduce the water mass fraction well below 50%, making the composition of these planets similar to those of solar system comets. Here we show that soot-rich planets, with or without water, can account for the low average densities of exoplanets that were previously attributed to a binary combination of rock and water. Formed in locations beyond the soot and/or snow lines in disks, these planets are likely common in our galaxy and already observed by JWST. The surfaces and interiors of soot-rich planets will be influenced by the chemical and physical properties of carbonaceous phases, and the atmospheres of such planets may contain plentiful methane and other hydrocarbons, with implications for photochemical haze generation and habitability.

Keywords: Exoplanet structure, Exoplanet formation
Genesis-metallicity: Universal Nonparametric Gas-phase Metallicity Estimation. We introduce genesis-metallicity, a gas-phase metallicity measurement Python software employing the direct and strong-line methods depending on the available oxygen lines. The nonparametric strong-line estimator is calibrated based on a kernel density estimate in the four-dimensional space of O2 = [O II]λλ3727,29/Hβ; O3 = [O III]λ5007/Hβ; Hβ equivalent width EW(Hβ); and gas-phase metallicity  12+log(O/H) . We use a calibration sample of 1510 galaxies at 0 &lt; z &lt; 10 with direct-method metallicity measurements, compiled from the JWST/NIRSpec and ground-based observations. In particular, we report 122 new NIRSpec direct-method metallicity measurements at z &gt; 1. We show that the O2, O3, and EW(Hβ) measurements are sufficient for a gas-phase metallicity estimate that is more accurate than 0.09 dex. Our calibration is universal, meaning that its accuracy does not depend on the target redshift. Furthermore, the direct-method module employs a nonparametric Te(O II) electron temperature estimator based on a kernel density estimate in the five-dimensional space of O2, O3, EW(Hβ), Te(O II), and Te(O III). This Te(O II) estimator is calibrated based on 1004 spectra with detections of both [O III]λ4363 and [O II]λλ7320,30, notably reporting 20 new NIRSpec detections of the [O II]λλ7320,30 doublet. We make genesis-metallicity and its calibration data publicly available and commit to keeping both up to date in light of the incoming data.

Keywords: Metallicity, Chemical enrichment, High-redshift galaxies, Interstellar medium
On the Orbital Evolution of Binaries with Polar Circumbinary Disks. Binaries occur in many astrophysical systems, from young protostellar binaries in star-forming regions to supermassive black hole binaries in galaxy centers. In many cases, a circumbinary disk of gas forms around the binary with an orbit that may be misaligned to the binary plane. Misaligned disks around nearly circular binaries evolve into disks that are either aligned or counteraligned with the binary orbit. However, if the binary is sufficiently eccentric, then it can be more likely that the disk will end up in a polar-aligned configuration in which the disk angular momentum vector aligns with the binary eccentricity vector. We use smoothed particle hydrodynamics simulations, evolved to an approximate steady state under mass injection, to determine the orbital evolution of a binary with a polar-aligned disk for a range of binary-disk parameters. We find that, in all of the cases we have simulated, the binary shrinks with time. The decay rate is larger than for binaries surrounded by aligned or retrograde disks with matched disk parameters. The rate of shrinkage is largely unaltered by the size of the sink radii employed for the binary stars, but for small enough sink radii some of the models exhibit long-lived polar circumprimary disks, which are continually fed mass from the circumbinary disk. We discuss our results in the contexts of planet formation in young polar-aligned disks and merging supermassive black holes in galaxy centers.

Keywords: Accretion, Supermassive black holes, Computational astronomy, Binary stars, Circumstellar disks, Exoplanet formation
Exploring the Dominant Process of Solar Toroidal Magnetic Flux Loss. As the solar magnetic cycle evolves, subsurface toroidal magnetic flux is systematically generated and lost, and this work aims to identify the dominant process behind the flux loss. By employing a data-driven dynamo model and holding surface magnetic flux transport identical across cycles 12─21, we conducted numerical experiments to isolate and assess the loss of subsurface toroidal flux, and then compared the results with two observational constraints: the butterfly diagram and the observed correlation between the polar field at cycle minimum and the strength of the next cycle. We found that under weak bulk diffusivity, the loss of the previous cycle's toroidal flux is dominated by cancellation by newly generated flux, causing the new cycle's actual flux to differ from its generated value and thereby preventing the simulation of the observed polar field─cycle strength correlation. When diffusivity is increased to a level where it dominates flux loss, residual flux is more effectively removed, restoring the polar field─cycle strength correlation; yet operating in the diffusion-dominated regime suppresses the formation of the butterfly diagram. In contrast, active region emergence acts as an efficient mechanism for removing residual flux, and when it dominates the flux loss, both the correlation and the butterfly diagram are successfully reproduced. Thus, we conclude that active region emergence dominates the subsurface toroidal flux loss.

Keywords: Solar magnetic fields, Sunspot cycle, Solar dynamo
Stellar-wind-blown Bubbles as Environments for Late-time Rebrightening of Gamma-ray Burst Afterglows. We present multiwavelength afterglow fitting results for three events that exhibit late afterglow rebrightening behavior: EP240414a (z = 0.401), GRB 240529A (z = 2.695), and GRB 240218A (z = 6.782), which span a broad range of redshifts, from the local to the high-redshift Universe. We prove that the peculiar afterglow light curves of the three bursts can be well fitted by structured jets propagated in the free-to-shocked-stellar-wind environment of stellar-wind-blown bubbles. This scenario offers a self-consistent explanation for the observed subclass of afterglows that exhibit rebrightening that is characterized by steep rises and rapid decays. It also provides a unified solution for such events and offers pathways for studying both the jet generation mechanism and the propagation processes of jets through the envelope of the progenitor. This study reveals that the structured jets produced by such events exhibit a narrow jet core and a steep angle-dependent energy decay index, suggesting highly magnetized jets. The derived transition radii from free stellar winds to shocked stellar winds for all three events are smaller than 0.5 pc, with statistical analysis of similar events indicating a median value of 0.1 pc, which conflicts with numerical simulation results. We anticipate that future observations by the Einstein Probe and SVOM missions will enhance the understanding of analogous events and further reveal information about progenitors and their circum-environments.

Keywords: Gamma-ray bursts, High energy astrophysics
Response of Martian Tail Lobes to Heliospheric Current Sheet: Tianwen-1 and MAVEN Joint Observations. Martian magnetotail lobes, mainly formed by the draped interplanetary magnetic field extending downstream in the tailward direction, are largely controlled by the solar wind and respond sensitively to variations in upstream drivers. However, due to the limitations of single-spacecraft observations, the real-time observational evidence for the response of Martian far magnetotail lobes to the heliospheric current sheet (HCS) has not been reported so far. Here, using Tianwen-1 and Mars Atmosphere and Volatile Evolution (MAVEN) data, we report for the first time the response of Martian far magnetotail lobes to the HCS. In our event, MAVEN monitored the HCS originating from the solar wind, and Tianwen-1 subsequently detected the reversal of the tail lobe orientation in the far magnetotail without signatures of magnetic reconnection. The results provide real-time observational evidence of the Martian far magnetotail lobe polarity reversal caused by the HCS, with a response time on the order of minutes.

Keywords: Mars, Solar wind, Solar-planetary interactions, Planetary science, Planetary magnetospheres
The Magnitude of the Dark Ages 21 cm Signal in the Context of Existing Early and Late Time Constraints on ΛCDM. The dark ages 21 cm signal is a promising probe of the currently unobserved infant Universe between the formation of the cosmic microwave background around z ≍ 1100 and the first galaxies around z ≍ 30. A detection of the signal will help researchers understand the nature of dark matter and dark energy, the expansion of the Universe, and any extensions to the concordance ΛCDM model that could explain the reported cosmic dawn 21 cm signal from EDGES and the Hubble tension. In this Letter we take existing constraints on the ΛCDM cosmological model from two early time probes, Planck and the Wilkinson Microwave Anisotropy Probe, and two late time probes, Dark Energy Survey galaxy lensing and clustering and baryon acoustic oscillations, and propagate these through to constraints on the magnitude of the dark ages 21 cm signal. We constrain the magnitude and central frequency of the signal while methodically accounting for uncertainties in the cosmological parameters. We find that within the context of our modeling assumptions and the ΛCDM paradigm, the depth of the dark ages 21 cm signal is known to better than 1 mK and the central frequency to within 0.05 MHz.

Keywords: Cosmology, H I line emission, Cosmological parameters
Intertwined Birth and Death: A Herbig─Haro Outflow Resolves the Distance to Vela Junior. The distance to the Vela Junior supernova remnant (RX J0852.0─4622 or G266.2─1.2) has long remained uncertain, limiting our understanding of its physical properties. Using Very Large Telescope/Multi Unit Spectroscopic Explorer integral field spectroscopy, we uncover chemical and kinematic connections between the nebula surrounding its central compact object (CXOU J085201.4─461753) and the nearby Herbig─Haro outflow of Ve 7─27 (Wray 16─30), indicating a shared nitrogen-rich, Fe-peak-enhanced environment. This link ties stellar birth and death, with the young star Ve 7─27 embedded in material expelled by Vela Junior's massive progenitor, and the remnant's blast wave is expanding through the same medium. Adopting the Gaia-based distance to Ve 7─27, we revise Vela Junior's distance to 1.41 ± 0.14 kpc. At this distance, the remnant's physical radius is 23.3 ± 2.3 pc, and X-ray proper motions of the northwestern rim correspond to shock speeds of (2.8 ± 0.7) × 103 to (5.6 ± 1.5) × 103 km s−1. These imply an age of ∼1.6─3.3 kyr and a very low ambient density, indicating that Vela Junior is expanding within a highly rarefied wind-blown cavity carved by a massive progenitor—consistent with the nondetection of strong thermal X-ray emission. This distance update also resolves long-standing inconsistencies, with major implications for its energy budget, particle acceleration efficiency, and compact object evolution.

Keywords: Supernova remnants, Compact nebulae, Herbig-Haro objects
Revised Active Galactic Nuclei Spectral Model Reveals a More Significant Role in Cosmic Reionization. Reionization marks one of the most important phase transitions in the history of the Universe, during which neutral baryonic matter was transformed into ionized plasma. While star-forming galaxies are widely regarded as the primary drivers of this process, the extent to which active galactic nuclei (AGN) contribute remains a subject of ongoing investigation. In this study, we integrate a physically motivated AGN spectral energy distribution (SED) model with state-of-the-art observations to reassess the contribution of AGN to cosmic reionization. Our findings indicate that adopting a more sophisticated AGN SED model could substantially increase the predicted ionizing photon output by a factor of 3 ∼ 4, elevating AGN to a more significant role (≍20%) in maintaining reionization than previously estimated. The inclusion of abundant faint AGN further amplifies this contribution by a factor of a few. These conclusions remain robust across a wide range of accretion rates and ionizing photon escape fractions. Collectively, our results suggest that AGN may have played a more prominent and previously underestimated role in the reionization of the Universe.

Keywords: Cosmology, Reionization, Galaxy formation, Active galactic nuclei