Sazuna/UAT_keywords huggingface dataset:
Carbon-rich Dust Injected into the Interstellar Medium by Galactic WC Binaries Survives for Hundreds of Years. Some carbon-rich Wolf–Rayet (WC) stars show an infrared excess from dust emission (WCd stars). Dust forms in the collision of the WC wind with a companion star's wind. As this dust is carried toward the interstellar medium (ISM) at close to the WCd wind speed and the binary continues through its orbit, a spiral structure forms around the system. The shape depends on the orbital eccentricity and period, as well as stellar parameters like mass-loss rates and terminal wind speeds. Imaging of the WCd binary WR 140 with JWST/MIRI revealed 17 concentric dust shells surrounding the binary. We present new JWST imaging of four additional WCd systems (WR 48a, WR 112, WR 125, and WR 137) that were imaged in 2024. In this analysis, we show that the dust is long-lived, detected with an age of at least 130 yr, but more than 300 yr in some systems. Longer-duration measurements are limited by sensitivity. Regular spacing of dust features confirms the periodic nature of dust formation, consistent with a connection to binary motion. We use these images to estimate the proper motion of the dust, finding the dust to propagate out to the ISM with motion comparable to the wind speed of the WC stars. In addition to these results, we observe unusual structures around WR 48a, which could represent dusty clumps shaped by photoevaporation and wind ablation like young proplyd objects. These results demonstrate that WC dust is indeed long-lived and should be accounted for in galactic dust budgets.

Keywords: WC stars, Binary stars, Stellar winds, Wolf-Rayet stars, Dust shells, Circumstellar dust
Variations in Dominant Wave Period in the Solar Atmosphere. Waves are an integral part of the solar atmosphere, and their characteristics (e.g., dominant period, range of periods, power, and phase angle) change on a diverse spatiotemporal scale. It is well established observationally that the dominant periods of solar oscillations are 5 and 3 minutes in the photosphere and chromosphere, respectively. This shows that the wave spectra and their dominant periods evolve between these two layers. We present observational results that demonstrate variations of the dominant period with heights in the photosphere and chromosphere. Six photospheric absorption lines and one chromospheric line are analyzed by using the Interface Region Imaging Spectrograph data, and the Doppler velocity time series at seven different atmospheric heights are determined. The wavelet analysis is applied to these time series, and the resulting spectrum of wave periods and its dominant period are deduced at these heights, which gives height variations of the dominant period. The obtained data show that the dominant period decreases with height and that there are also changes in the range of wave periods within the spectrum. Numerical simulations of filtered wave spectra through the solar atmosphere are also performed, and the obtained results match the observational data.

Keywords: Solar ultraviolet emission, Quiet sun, Atomic spectroscopy, Wavelet analysis, Solar oscillations
Low-velocity Precessing Jets Can Explain Observed Morphologies in the Twin Radio Galaxy TRG J104454+354055. Our understanding of large-scale radio jets in merger systems has been drastically improved in the era of the Very Large Array, Very Long Baseline Array/European VLBI Network, upgraded Giant Metrewave Radio Telescope, and MeerKAT. Twin radio galaxies (TRGs) are rare interacting galaxy pairs where both supermassive black holes host kiloparsec-scale bipolar radio jets. Only recently was a third TRG discovered, and it shows significantly different jet morphologies than the previous two. Due to both the extreme paucity and complexity of such systems, the launching of their jets as well as their mutual interaction during the propagation through the ambient medium are not well understood. We have performed three-dimensional hydrodynamic simulations to study the bipolar jets in the third TRG, J104454+354055. Our study indicates that the precession of mutually tilted bipolar jets originating from the two galactic nuclei separated by tens of kiloparsecs and propagating at low velocities can explain the observed morphologies. The simulated jet precession timescales are short compared to the overall dynamical timescale of the jets, and could originate from Lense–Thirring effect in the accretion disks. This approach to understanding TRG jet dynamics could also be applied to other TRG systems with similar helical morphologies that may be discovered in the upcoming era of the Square Kilometre Array and its pathfinder surveys.

Keywords: Galaxy clusters, Supermassive black holes, Radio jets, Quasars, Quasar-galaxy pairs, Active galaxies, Galaxy jets
Continuum Enhancement and Line Asymmetries of Solar Flares in Different Heating Models: Alfvén Waves, Nonthermal Electron Beams, and Their Joint Effect. How the plasma in the atmosphere is heated during a solar flare remains inconclusive. Nonthermal electron beams are usually considered as an essential heating source, yet Alfvén waves have also been proposed as a promising heating mechanism. Based on radiative hydrodynamic simulations, we explored the performance of different heating mechanisms, including nonthermal electron beams, Alfvén waves, and their joint effects. We studied the parameter space of Alfvén waves, focusing on the heating depth and the continuum emissions at 3600 and 6170 Å. We compared the atmospheric structures, continuum enhancements, and line profiles of hydrogen Lyα and Hα in beam-heated, wave-heated, and jointly heated flare models. We find that the heating location of waves is strongly dependent on the wavenumber and frequency. The Alfvén wave can penetrate into the lower chromosphere and even the photosphere, causing a prominent continuum emission. There are different atmospheric responses in the Alfvén-wave and electron-beam heating cases due to their different energy-damping patterns. However, there seem to be no unique features in the Lyα and Hα line profiles that can be used to distinguish the wave-heated models. In the jointly heated cases, the heating effect of waves and that of energetic electron beams can affect each other during the evolution of flares. Our simulations provide some references for interpreting the observed line profiles as well as the continuum emissions in solar white-light flares.

Keywords: Alfven waves, Solar flares, Radiative transfer, Solar flare spectra
Channels of Stellar-mass Black Hole Formation. On the basis of a large collection of detailed 3D core-collapse supernova simulations carried to late times, we identify four channels of stellar-mass black hole formation. Our examples for Channel 1 can involve the formation of black holes in energetic asymmetric supernova explosions. Our Channel 2 example involves a modest supernova explosion that nevertheless leaves behind a black hole. The latter may not be easily distinguishable from "standard" supernovae that birth neutron stars. Our Channel 3 example experiences an aborted core-collapse explosion, more often in the context of a low-metallicity progenitor, whose residue is a black hole with a mass perhaps up to ∼40 M⊙. The latter may be accompanied by a pulsational pair-instability supernova. Channel 4 is the only quiescent or "silent" scenario for which perhaps ∼5–15 M⊙ black holes are left. Where appropriate, we estimate 56Ni yields, explosion energies, approximate recoil speeds, and residual black hole masses. The progenitor mass density and binding energy profiles at collapse influence the outcome in a systematic way. We speculate that the statistics and prevalence of these various channels depend not only on still evolving supernova theory, but on remaining issues with the theory of massive star evolution, binary interaction, wind mass loss, metallicity, and the nuclear equation of state. Importantly, we suggest, but have not proven, that the silent channel for black hole formation may not be the dominant formation modality.

Keywords: Stellar mass black holes, Core-collapse supernovae
Can We Discover Physical Models Using Machine Learning? A Case Study of Galaxy Sizes. We explore the ability of machine learning methods to discover underlying equations of physics by searching for the equations governing galaxy size in a semianalytic model. This case study allows us to evaluate the process as we know the ground truth. We find that we fail to find an equation to predict galaxy size on the entire data set, but are successful when we separate out disk galaxies where we expect the physics driving galaxy size to be different than in bulge-dominated systems. We are also able to find an equation for bulge size, but not without adding an additional feature based on our knowledge of elliptical galaxy scaling relations.

Keywords: Elliptical galaxies, Disk galaxies
Deep Galaxy Stellar Mass Functions As a Function of Star Formation Rate in the Virgo Cluster Environment. We analyze deep (M* ≳ 107 M⊙) galaxy stellar mass functions (SMFs) of the Virgo cluster using stellar masses derived as part of the Next Generation Virgo Survey. The total SMF has a slope of  α=‑1.35‑0.02+0.02 , which is similar to or steeper than typical field values. Using deep Hα data from the Virgo Environmental Survey Tracing Ionised Gas Emission we separate out star-forming galaxies, quiescent galaxies with no ongoing star formation, and low star formation rate (SFR) galaxies that are intermediate between these two populations. For each of these populations, the shape of the SMF is found to be universal throughout the cluster, from the core to the outskirts. The star-forming and quiescent SMFs show stark differences with values seen in field galaxies. The relative fraction of quiescent galaxies is highest in the core of the cluster, with low-SFR and star-forming galaxies more significant in the outer regions of the cluster. At low stellar masses (M* ≲ 109 M⊙), the quiescent fraction in the main cluster is significantly higher than that of the field and even satellites of massive groups. At high stellar masses, the quiescent fraction is similar to other studies of cluster galaxies. We model the quiescent population in the infall region of the cluster as a combination of backsplash and field quiescent galaxies, and find that the backsplash fractions needed to explain the observed population are unrealistically high. This suggests the existence of a third population of low-mass galaxies that are preprocessed outside the virial radius of the cluster, possibly in groups prior to infall.

Keywords: Galaxy clusters, Virgo Cluster, Stellar mass functions, Galaxy evolution, Stellar masses, Galaxies
The Multiband Emission of the Two-component Gamma-Ray Burst Jet Influenced by Progenitor Winds within the Accretion Disk of Active Galactic Nuclei. Gamma-ray bursts (GRBs), both from the merger of binary compact objects (short GRBs) and the collapse of massive stars (long GRBs), are expected to occur in dense environments, e.g., the accretion disks of active galactic nuclei (AGNs). The propagating of GRB jets in such dense environments will result in multiband transients. Investigating the properties of these transients plays an important role in their identification, understanding the jet structure, and constraining the population of the star and compact objects in AGNs disks. In this work, we study the propagation and emission of a two-component GRB jet (a fast narrow component and a wide slow one) in an AGN disk. We consider the influence of wind from short and long GRB progenitors, which reconstruct the surrounding density distribution and form a cavity in the AGN disk. We find that long GRB jets are choked, and the dynamics and emission resemble the case without a cavity. The cocoon breakout emission can be detected by Einstein Probe (EP) and Hard X-ray Modulation Telescope (HXMT). For short GRBs, we expect a nonthermal afterglow emission from the narrow and wide jet (if it is more energetic than the narrow one) and a cocoon breakout emission from the choked wide jet, which can be monitored by EP and HXMT, respectively. Therefore, joint observations by EP and HXMT might be helpful to distinguish the types of GRBs in AGNs disks and the jet components.

Keywords: Gamma-ray bursts, Galaxy accretion disks
Time-resolved p-mode Oscillations for Subgiant HD 142091 with NEID at WIYN. Detections of Earth-analog planets in radial velocity (RV) observations are limited by stellar astrophysical variability occurring on a variety of timescales. Current state-of-the-art methods to disentangle potential planet signals from intrinsic stellar signals assume that stellar signals introduce asymmetries to the line profiles that can therefore be separated from the pure translational Doppler shifts of planets. Here, we examine this assumption using a time series of resolved stellar p-mode oscillations in HD 142091 (κ CrB), as observed on a single night with the NEID spectrograph at 2 minutes cadence and with 25 cm s‑1 precision. As an evolved subgiant star, this target has p-mode oscillations that are larger in amplitude (4–8 m s‑1) and occur on longer timescales (80 minutes) than those of typical Sun-like stars of RV surveys, magnifying their corresponding effects on the stellar spectral profile. We show that for HD 142091, p-mode oscillations manifest primarily as pure Doppler shifts in the average line profile—measured by the cross-correlation function (CCF)—with "shape-driven" CCF variations as a higher-order effect. Specifically, we find that the amplitude of the shift varies across the CCF bisector, with 10% larger oscillation amplitudes closer to the core of the CCF and 25% smaller oscillation amplitudes for bisector velocities derived near the wings; we attribute this trend to larger oscillation velocities higher in the stellar atmosphere. Using a line-by-line analysis, we verify that a similar trend is seen as a function of average line depth, with deeper lines showing larger oscillation amplitudes. Finally, we find no evidence that p-mode oscillations have a chromatic dependence across the NEID bandpass beyond that due to intrinsic line depth differences across the spectrum.

Keywords: Stellar oscillations, Radial velocity
Unveiling the Complex Jet Dynamics in the Blazar 2021+317 through Multiepoch Very Long Baseline Interferometry Observations. We present an investigation of the compact structure of the active galactic nucleus 2021+317 based on multiepoch very long baseline interferometry (VLBI) observations at 15, 22, and 43 GHz in the period from 2013 through 2024. The VLBI images show a core─jet structure extended to the south, with two stationary components in the northern region, one of which is likely to be the core of the source. We also detected two new moving jet components (S4 and S5) in the observations of 2021. Based on these observational findings, we analyzed two distinctive jet models involving one or another stationary component mentioned above as the jet core. One model assumes a moderate bulk motion velocity, a wider viewing angle, and a lower Doppler factor, with the magnetic field energy density significantly dominating over the nonthermal particle energy density. The other model involves a higher bulk motion velocity, a narrower viewing angle, and a higher Doppler factor, with an even greater dominance of magnetic field energy in the core. The position angle of the jet ridgeline rotates counterclockwise over the observed period. The apparent kinematics of the jet components is more consistent with a model of the precessing jet, which has recently completed the first half of the precession cycle. Our results provide constraints on the dynamic evolution of the jet and its interaction with the surrounding medium.

Keywords: BL Lacertae objects, Very long baseline interferometry, Active galactic nuclei
Searching for Radio Transients with Inverted Spectra in Epoch 1 of VLASS and VCSS, and Identification of a Sample of Candidate Relativistic Nuclear Transients. For radio transients, an inverted spectrum (defined as α &gt; 0 for a power-law spectrum Sν ∝ να) constrains physical properties, which in principle can be a useful criterion for selecting specific targets of interest in a transient search. To test and develop this concept, we have searched epoch 1 of the Very Large Array Sky Survey (VLASS; 3.0 GHz) and the VLITE Commensal Sky Survey (VCSS; 340 MHz) for radio transients with inverted spectra. We discover a sample of 21 inverted-spectra transient candidates that are not associated with cataloged active galactic nuclei (AGNs). To the best of our knowledge, three of our candidates have recently been reported by others as radio transients, but none have reported transient counterparts at other wavelengths. We find that our candidates evolve slowly over years and show either highly inverted spectra or peaked spectra over ∼1–3 GHz. Within our sample, nine candidates are matched to optical centers of galaxies and have estimated radio spectral luminosities of L3.0GHz ∼ 1030–1033 erg s‑1 Hz‑1. Based on the observed properties, we find the most plausible transient classification for our candidates to be relativistic tidal disruption events. However, it is difficult to rule out variable or transient AGNs with highly inverted spectra. Upon examining physical constraints, we confirm that mainly relativistic transients (on-axis or off-axis) with equipartition energy Eeq ≳ 1049–1053 erg are expected from searching VLASS and VCSS based on inverted spectra. The obtainable physical constraints, however, can be weak due to degeneracy introduced by viewing angle.

Keywords: Radio jets, Surveys, Tidal disruption, Transient sources, Active galactic nuclei
The Secular Periodic Evolution of X-Ray Quasiperiodic Eruptions Driven by Star−Disk Collisions. We study the secular periodic evolution of quasiperiodic eruptions (QPEs) for GSN069 and eRO-QPE2 assuming that they are driven by star−disk collisions. We set up numerical simulations and compared them with the observed periodic decay of ∼−3160 ± 720 s yr−1 in GSN069 and ∼−370 ± 40 s yr−1 in eRO-QPE2. We find the following: (1) Stellar-mass black holes are unlikely to be the orbiters in these two sources, as their periodic decays are on the order of &lt;10 s yr−1. (2) A naked degenerate core (including a white dwarf) is unlikely to be the orbiter in GSN069, as the decay is on the order of &lt;200 s yr−1. However, it is possible in eRO-QPE2, although the required surface density of the accretion disk is relatively high (e.g., Σ ≳ 107─108 g cm−2). (3) Both the orbiters in GSN069 and eRO-QPE2 can be solar-like main-sequence (MS) stars. However, each collision can lead to gradual ablation of the stellar envelope on the order of 10−5 to 10−3 M⊙. To reproduce the observed decay while surviving for ≳3 yr, the surface density of the disk needs to be within a certain range. For example, given a 1 M⊙ MS orbiter, the surface density of the disk gas should be in the range of 3 × 105 g cm−2 to 2 × 106g cm−2 for GSN069 or 5 × 104 g cm−2 to 106 g cm−2 for eRO-QPE2. In both of these sources, the MS star cannot survive for more than ∼12 yr. We expect that future observations of these two sources can help to distinguish whether the orbiters are degenerated compact objects or gaseous stars.

Keywords: Accretion, Supermassive black holes, High energy astrophysics, X-ray active galactic nuclei, Compact objects, Main sequence stars
Absence of a Runaway Greenhouse Limit on Lava Planets. Climate transitions on exoplanets offer valuable insights into the atmospheric processes governing planetary habitability. Previous pure-steam atmospheric models show a thermal limit in outgoing long-wave radiation, which has been used to define the inner edge of the classical habitable zone and guide exoplanet surveys aiming to identify and characterize potentially habitable worlds. We expand upon previous modelling by treating (i) the dissolution of volatiles into a magma ocean underneath the atmosphere, (ii) a broader volatile range of the atmospheric composition including H2O, CO2, CO, H2, CH4, and N2, and (iii) a surface-temperature- and mantle-redox-dependent equilibrium chemistry. We find that multicomponent atmospheres of outgassed composition located above partially or fully molten mantles do not exhibit the characteristic thermal radiation limit that arises from pure-steam models, thereby undermining the canonical concept of a runaway greenhouse limit, and hence challenging the conventional approach of using it to define an irradiation-based habitable zone. Our results show that atmospheric heat loss to space is strongly dependent on the oxidation and melting state of the underlying planetary mantle, through their significant influence on the atmosphere's equilibrium composition. This suggests an evolutionary hysteresis in climate scenarios: Initially molten and cooling planets do not converge to the same climate regime as solidified planets that heat up by external irradiation. Steady-state models cannot recover evolutionary climate transitions, which instead require self-consistent models of the temporal evolution of the coupled feedback processes between interior and atmosphere over geologic time.

Keywords: Extrasolar rocky planets, Atmospheric evolution, Exoplanets, Planetary atmospheres, Planetary thermal histories, Exoplanet evolution, Planetary science, Planetary climates, Habitable planets
Rotation Measure Jitter: Wavelength-dependent Scatter in Rotation Measure Related to Faraday Complexity. The relation between Faraday rotation measure (RM) and differential Faraday rotation by unresolved structure of a turbulent plasma is investigated for extragalactic radio sources. The RM scatter of a sample of sources affected by turbulent Faraday screens with identical power spectra of Faraday depth structure is referred to as RM jitter. For fixed amplitude and slope of the power spectrum, the range of possible RMs depends on the wavelength coverage of the survey. RM jitter is independent of Faraday depth resolution as it results from the true Faraday depth dispersion and effects of wavelength-dependent depolarization. RM jitter for a flux-density-limited sample is sensitive to the power-law index γ of the power spectrum of Faraday depth structure. Assuming depolarization by a turbulent Faraday screen for all sources, a simulated flux-density-limited sample can reproduce the high RM scatter found by S. Vanderwoude et al. (2024) for sources that are less than 3% polarized. RM jitter of sources that are more than 3% polarized is found to be smaller than the observed scatter, indicating that plasma other than the near-source environment dominates the RM scatter for the more polarized sources. The significance of RM jitter for applications of the RM grid is discussed.

Keywords: Radio continuum emission, Extragalactic radio sources, Radio source catalogs, Extragalactic magnetic fields