Sazuna/UAT_keywords huggingface dataset:
UNCOVER: JWST Spectroscopy of Three Cold Brown Dwarfs at Kiloparsec-scale Distances. We report JWST/NIRSpec spectra of three distant T-type brown dwarfs identified in the Ultradeep NIRSpec and NIRCam ObserVations before the Epoch of Reionization (UNCOVER) survey of the Abell 2744 lensing field. One source was previously reported as a candidate T dwarf on the basis of NIRCam photometry, while two sources were initially identified as candidate active galactic nuclei. Low-resolution 1–5 μm spectra confirm the presence of molecular features consistent with T dwarf atmospheres, and comparison to spectral standards infers classifications of sdT1, T6, and T8–T9. The warmest source, UNCOVER-BD-1, shows evidence of subsolar metallicity, and atmosphere model fits indicate T eff = 1300 K and [M/H] ∼ ‑1.0, making this one of the few spectroscopically confirmed T subdwarfs known. The coldest source, UNCOVER-BD-3, is near the T/Y dwarf boundary with T eff = 550 K, and our analysis indicates the presence of PH3 in the 3–5 μm region, favored over CO2 and a possible indicator of subsolar metallicity. We estimate distances of 0.9–4.5 kpc from the Galactic midplane, making these the most distant brown dwarfs with spectroscopic confirmation. Population simulations indicate high probabilities of membership in the Galactic thick disk for two of these brown dwarfs, and potential halo membership for UNCOVER-BD-1. Our simulations indicate that there are approximately 5 T dwarfs and 1–2 L dwarfs in the Abell 2744 field down to F444W = 30 AB mag, roughly one-third of which are thick disk members. These results highlight the utility of deep JWST/NIRSpec spectroscopy for identifying and characterizing the oldest metal-poor brown dwarfs in the Milky Way.

Keywords: Brown dwarfs, Sky surveys, Milky Way stellar halo, T subdwarfs, T dwarfs
Predicting the Arrival Time of an Interplanetary Shock Based on DSRT Spectrum Observations for the Corresponding Type II Radio Burst and a Blast Wave Theory. Since fast head-on coronal mass ejections and their associated shocks represent potential hazards to the space environment of the Earth and even other planets, forecasting the arrival time of the corresponding interplanetary shock is a priority in space weather research and prediction. Based on the radio spectrum observations of the 16-element array of the Daocheng Solar Radio Telescope (DSRT), the flagship instrument of the Meridian Project of China, during its construction, this study determines the initial shock speed of a type II solar radio burst on 2022 April 17 from its drifting speed in the spectrum. Assuming that the shock travels at a steady speed during the piston-driven phase (determined from the X-ray flux of the associated flare) and then propagates through interplanetary space as a blast wave, we estimate the propagation and arrival time of the corresponding shock at the orbit of the Solar Terrestrial Relations Observatory-A (STEREO-A). The prediction shows that the shock will reach STEREO-A at 14:31:57 UT on 2022 April 19. The STEREO-A satellite detected an interplanetary shock at 13:52:12 UT on the same day. The discrepancy between the predicted and observed arrival time of the shock is only 0.66 hr. The purpose of this paper is to establish a general method for predicting the shock's propagation and arrival time from this example, which will be utilized to predict more events in the future based on the observations of ground-based solar radio spectrometers or telescopes like DSRT.

Keywords: Interplanetary shocks, Theoretical models, Space weather, Radio bursts, Solar coronal mass ejections
An X-Ray Synchrotron Shell and a Pulsar: The Peculiar Supernova Remnant G32.4+0.1. We present a deep Chandra observation of the shell supernova remnant (SNR) G32.4+0.1, whose featureless X-ray spectrum has led to its classification as an X-ray synchrotron-dominated SNR. We find a partial shell morphology whose outline is quite circular, with a radius of about 11 pc at an assumed distance of 11 kpc. Thermal and power-law spectral models for three relatively bright regions provided equally good fits, but the absence of spectral lines required ionization timescales from thermal fits that are inconsistent with the mean densities derived from emission measures. We thus confirm the nonthermal, i.e., synchrotron, origin of X-rays from G32.4+0.1. Shock velocities needed to accelerate electrons to the required TeV energies are ≳1000 km s‑1, giving a remnant age ≲ 5000–9000 yr. There is no obvious X-ray counterpart to the radio pulsar PSR J1850‑0026, but its position adjoins a region of X-ray emission whose spectrum is somewhat harder than that of other regions of the shell, and which may be a pulsar-wind nebula (PWN), though its spectrum is steeper than almost all known X-ray PWNe. The distance of the pulsar from the center of symmetry of the shell disfavors a birth in a supernova event at that location only a few thousand years before; either the pulsar (and putative PWN) are not associated with the shell SNR, requiring a coincidence of both position and (roughly) absorbing column density, or the SNR is much older, making the origin of nonthermal emission problematic.

Keywords: Supernova remnants, Pulsars, Pulsar wind nebulae
Relativistic Jet Motion in the Radio-quiet LINER Galaxy KISSR 872. We report superluminal jet motion with an apparent speed of β app = 1.65 ± 0.57 in the radio-quiet (RQ) low-ionization nuclear emission-line region (LINER) galaxy KISSR 872. This result comes from two-epoch phase-referenced very long baseline interferometry observations at 5 GHz. The detection of bulk relativistic motion in the jet of this extremely radio-faint active galactic nucleus (AGN), with a total 1.4 GHz flux density of 5 mJy in the 5.″4 resolution Very Large Array FIRST survey image and 1.5 mJy in the ∼5 mas resolution Very Long Baseline Array image, is the first of its kind in an RQ LINER galaxy. The presence of relativistic jets in lower accretion rate objects like KISSR 872, with an Eddington ratio of 0.04, reveals that even RQ AGN can harbor relativistic jets and provides evidence of their universality over a wide range of accretion powers.

Keywords: LINER galaxies
Reconnection along a Separator in Shock Turbulence. Numerous structures conducive to magnetic reconnection are frequently observed in the turbulent regions at quasi-parallel shocks. In this work, we use a particle-in-cell simulation to study 3D magnetic reconnection in shock turbulence. We identify and characterize magnetic null points, and focus on reconnection along the separator between them. We identify a reconnection region with strong parallel current, a finite parallel potential, and counterrotating electron flows. Electrons are shown to be accelerated by the parallel electric field before being scattered at the null.

Keywords: Space plasmas, Planetary bow shocks, Plasma physics
Simulating Compressive Stream Interaction Regions during Parker Solar Probe's First Perihelion Using Stream-aligned Magnetohydrodynamics. We used the stream-aligned magnetohydrodynamics (SA-MHD) model to simulate Carrington rotation 2210, which contains Parker Solar Probe's (PSP) first perihelion at 36.5 R ⊙ on 2018 November 6, to provide context to the in situ PSP observations by FIELDS and SWEAP. The SA-MHD model aligns the magnetic field with the velocity vector at each point, thereby allowing for clear connectivity between the spacecraft and the source regions on the Sun, without unphysical magnetic field structures. During this Carrington rotation, two stream interaction regions (SIRs) form, due to the deep solar minimum. We include the energy partitioning of the parallel and perpendicular ions and the isotropic electrons to investigate the temperature anisotropy through the compression regions to better understand the wave energy amplification and proton thermal energy partitioning in a global context. Overall, we found good agreement in all in situ plasma parameters between the SA-MHD results and the observations at PSP, STEREO-A, and Earth, including at PSP's perihelion and through the compression region of the SIRs. In the typical solar wind, the parallel proton temperature is preferentially heated, except in the SIR, where there is an enhancement in the perpendicular proton temperature. This is further showcased in the ion cyclotron relaxation time, which shows a distinct decrease through the SIR compression regions. This work demonstrates the success of the Alfvén wave turbulence theory for predicting interplanetary magnetic turbulence levels, while self-consistently reproducing solar wind speeds, densities, and overall temperatures, including at small heliocentric distances and through SIR compression regions.

Keywords: Hydrodynamical simulations, Solar wind, Solar corona
Polarization Leakage and the IXPE Point-spread Function. By measuring photoelectron tracks, the gas pixel detectors of the Imaging X-ray Polarimetry Explorer satellite provide estimates of the photon detection location and its electric vector position angle (EVPA). However, imperfections in reconstructing event positions blur the image, and EVPA-position correlations result in artificial polarized halos around bright sources. We introduce a new model describing this "polarization leakage" and use it to recover the on-orbit telescope point-spread functions, useful for faint-source detection and image reconstruction. These point-spread functions are more accurate than previous approximations or ground-calibrated products (Δχ 2 ≈ 3 × 104 and 4 × 104 respectively for a bright 106-count source). We also define an algorithm for polarization leakage correction substantially more accurate than existing prescriptions (Δχ 2 ≈ 1 × 103). These corrections depend on the reconstruction method, and we supply prescriptions for the mission-standard "Moments" methods as well as for "Neural Net" event reconstruction. Finally, we present a method to isolate leakage contributions to polarization observations of extended sources and show that an accurate PSF allows the extraction of sub-PSF-scale polarization patterns.

Keywords: X-ray astronomy, Open source software, X-ray detectors, Pulsar wind nebulae, Polarimetry
The Energy-dependent Gamma-Ray Light Curves and Spectra of the Vela Pulsar in the Dissipative Magnetospheres. We study the pulsar energy-dependent γ-ray light curves and spectra from curvature radiation in the dissipative magnetospheres. The dissipative magnetospheres with the combined force-free (FFE) and Aristotelian are computed by a pseudo-spectral method with a high-resolution simulation in the rotating coordinate system, which produces a near-FFE field structure with the dissipative region only near the equatorial current sheet outside the light cylinder. We use the test-particle trajectory method to compute the energy-dependent γ-ray light curves and phase-average and phase-resolved spectra by including both the accelerating electric field and radiation reaction. The predicted energy-dependent γ-ray light curves and spectra are then compared with those of the Vela pulsar observed by Fermi. Our results can generally reproduce the observed trends of the energy-dependent γ-ray light curves and spectra for the Vela pulsar.

Keywords: Magnetic fields, Gamma-rays, Pulsars
Ultra–short-period WD Binaries Are Not Undergoing Strong Tidal Heating. Double white dwarf (WD) binaries are increasingly being discovered at short orbital periods where strong tidal effects and significant tidal heating signatures may occur. We assume that the tidal potential of the companion excites outgoing gravity waves within the WD primary, the dissipation of which leads to an increase in the WD's surface temperature. We compute the excitation and dissipation of the waves in cooling WD models in evolving MESA binary simulations. Tidal heating is self-consistently computed and added to the models at every time step. As a binary inspirals to orbital periods less than ∼20 minutes, the WD's behavior changes from cooling to heating, with temperature enhancements that can exceed 10,000 K compared with nontidally heated models. We compare a grid of tidally heated WD models to observed short-period systems with hot WD primaries. While tidal heating affects their T eff, it is likely not the dominant luminosity. Instead, these WDs are probably intrinsically young and hot, implying that the binaries formed at short orbital periods. The binaries are consistent with undergoing common envelope evolution with a somewhat low efficiency α CE. We delineate the parameter space where the traveling wave assumption is most valid, noting that it breaks down for WDs that cool sufficiently, where standing waves may instead be formed.

Keywords: Close binary stars, White dwarf stars, Stellar evolutionary models, Tidal interaction, Common envelope evolution
Heliospheric Diffusion of Stochastic Parker Spirals in Radially Evolving Solar Wind Turbulence. We present a stochastic field line mapping model where the interplanetary magnetic field lines are described by a density distribution function satisfying a Fokker–Planck equation that is solved numerically. Due to the spiral geometry of the nominal Parker field and to the evolving nature of solar wind turbulence, the heliospheric diffusion of the magnetic field lines is both heterogeneous and anisotropic, including a radial component. The longitudinal distributions of the magnetic field lines are shown to be close to circular Gaussian distributions, although they develop a noticeable skewness. The magnetic field lines emanating from the Sun are found to differ, on average, from the spirals predicted by Parker. Although the spirals remain close to Archimedean, they are here underwound, on average. Our model predicts a spiral angle that is smaller by ∼5° than the Parker spiral angle at Earth's orbit for the same solar wind speed of V sw = 400 km s‑1. It also predicts an angular position on the solar disk of the best magnetically connected footpoint to an observer at 1 au that is shifted westward by ∼10° with respect to the Parker's field model. This significantly changes the angle of the most probable magnetic connection between possible sources on the Sun and observers in the inner heliosphere. The results have direct implications for the heliospheric transport of "scatter-free" electrons accelerated in the aftermath of solar eruptions.

Keywords: Interplanetary turbulence, Interplanetary magnetic fields
Absorption of Millimeter-band CO and CN in the Early Universe: Molecular Clouds in the Radio Galaxy B2 0902+34 at Redshift 3.4. Using the Karl G. Jansky Very Large Array, we have detected absorption lines due to carbon monoxide, CO(J = 0 → 1), and the cyano radical, CN(N = 0 → 1), associated with radio galaxy B2 0902+34 at redshift z = 3.4. The detection of millimeter-band absorption observed 1.5 Gyr after the Big Bang facilitates studying molecular clouds down to gas masses inaccessible to emission-line observations. The CO absorption in B2 0902+34 has a peak optical depth of τ ≥ 8.6% and consists of two components, one of which has the same redshift as previously detected 21 cm absorption of neutral hydrogen (H I) gas. Each CO component traces an integrated H2 column density of ${N}_{{{\rm{H}}}_{2}}$ ≳ 3 × 1020 cm‑2. CN absorption is detected for both CO components, as well as for a blueshifted component not detected in CO, with CO/CN line ratios ranging from ≲0.4 to 2.4. We discuss the scenario that the absorption components originate from collections of small and dense molecular clouds that are embedded in a region with more diffuse gas and high turbulence, possibly within the influence of the central active galactic nucleus or a starburst region. The degree of reddening in B2 0902+34, with rest-frame color B ‑ K ∼ 4.2, is lower than the very red colors (B ‑ K &gt; 6) found among other known redshifted CO absorption systems at z &lt; 1. Nevertheless, when including the many nondetections from the literature, a potential correlation between the absorption-line strength and B ‑ K color is evident, giving weight to the argument that the red colors of CO absorbers are due to a high dust content.

Keywords: Radio spectroscopy, Quasar absorption line spectroscopy, Cosmological parameters, Galaxy jets, Molecular clouds, Extinction, Galaxy evolution, Radio sources
Deep Chandra Observation of the Remarkable Ionization Cones of NGC 5252. Seyfert galaxy NGC 5252 harbors enormously extended ionization cones that have been previously detected in the optical and X-ray band, offering a unique opportunity to investigate the interaction between the central active galactic nucleus (AGN) and the surrounding gas in the AGN host galaxy. We present deep Chandra imaging spectroscopy of NGC 5252 with a total exposure time of 230 ks. The morphology in the soft X-rays shows resolved extended structure from the nucleus to a large radial distance, and for the first time we detect the outermost X-ray arc at ∼20 kpc. The X-ray cone mostly follows the direction of the optical ionization cones in the southeast and northwest directions, about 20° misaligned with the major axis of the galactic disk of NGC 5252. Fitting the spectra extracted from radial sectors with photoionization models supports that extended emission is mainly photoionized by the central AGN. We also examine the variation of the photoionization parameter along the radial extension and infer a decreasing ionizing continuum of the central engine by a factor of ∼50 over the past 64,000 yr. These findings are consistent with previous suggestions that NGC 5252 resembles a quasar relic with an M ∼ 109 M ⊙ supermassive black hole that went through a minor merger event and switched to a low accretion rate state.

Keywords: AGN host galaxies, Photoionization, X-ray active galactic nuclei, Hot ionized medium
Solar Tachocline Confinement by the Nonaxisymmetric Modes of a Dynamo Magnetic Field. We recently presented the first 3D numerical simulation of the solar interior for which tachocline confinement was achieved by a dynamo-generated magnetic field. In this follow-up study, we analyze the degree of confinement as the magnetic field strength changes (controlled by varying the magnetic Prandtl number) in a coupled radiative zone (RZ) and convection zone (CZ) system. We broadly find three solution regimes, corresponding to weak, medium, and strong dynamo magnetic field strengths. In the weak-field regime, the large-scale magnetic field is mostly axisymmetric with regular, periodic polarity reversals (reminiscent of the observed solar cycle) but fails to create a confined tachocline. In the strong-field regime, the large-scale field is mostly nonaxisymmetric with irregular, quasi-periodic polarity reversals and creates a confined tachocline. In the medium-field regime, the large-scale field resembles a strong-field dynamo for extended intervals but intermittently weakens to allow temporary epochs of strong differential rotation. In all regimes, the amplitude of poloidal field strength in the RZ is very well explained by skin-depth arguments, wherein the oscillating field that gives rise to the skin depth (in the medium- and strong-field cases) is a nonaxisymmetric field structure at the base of the CZ that rotates with respect to the RZ. These simulations suggest a new picture of solar tachocline confinement by the dynamo, in which nonaxisymmetric, very long-lived (effectively permanent) field structures rotating with respect to the RZ play the primary role, instead of the regularly reversing axisymmetric field associated with the 22 yr cycle.

Keywords: Solar radiative zone, Solar differential rotation, Solar interior, Solar convective zone, Solar dynamo
Discrepancies in the Properties of a Coronal Mass Ejection on Scales of 0.03 au as Revealed by Simultaneous Measurements at Solar Orbiter and Wind: The 2021 November 3–5 Event. Simultaneous in situ measurements of coronal mass ejections (CMEs), including both plasma and magnetic field, by two spacecraft in radial alignment have been extremely rare. Here, we report on one such CME measured by Solar Orbiter (SolO) and Wind on 2021 November 3–5, while the spacecraft were radially separated by a heliocentric distance of 0.13 au and angularly by only 2.2°. We focus on the magnetic cloud (MC) part of the CME. We find notable changes in the R and N magnetic field components and in the speed profiles inside the MC between SolO and Wind. We observe a greater speed at the spacecraft farther away from the Sun without any clear compression signatures. Since the spacecraft are close to each other and computing fast magnetosonic wave speed inside the MC, we rule out temporal evolution as the reason for the observed differences, suggesting that spatial variations over 2.2° of the MC structure are at the heart of the observed discrepancies. Moreover, using shock properties at SolO, we forecast an arrival time 2 hr 30 minutes too late for a shock that is just 5 hr 31 minutes away from Wind. Predicting the north–south component of the magnetic field at Wind from SolO measurements leads to a relative error of 55%. These results show that even angular separations as low as 2.2° (or 0.03 au in arc length) between spacecraft can have a large impact on the observed CME properties, which raises the issue of the resolutions of current CME models, potentially affecting our forecasting capabilities.

Keywords: Solar coronal mass ejections, Heliosphere
Hydrodynamic Simulations of Oxygen–Neon Classical Novae as Galactic <SUP>7</SUP>Li Producers and Potential Accretion-induced Collapse Progenitors. We report on studies of classical nova (CN) explosions where we follow the evolution of thermonuclear runaways (TNRs) on oxygen–neon (ONe) white dwarfs (WDs). Using NOVA, a 1D hydrodynamic computer code, we accrete solar matter until the TNR is ongoing and then switch to a mixed composition. This approach is guided by the results of multidimensional studies of TNRs in WDs, which find that sufficient mixing with WD core material occurs after the TNR is well underway, and levels of enrichment of the CNONeMg elements are reached that agree with observations of CN ejecta abundances. Because the amount of accreted material is inversely proportional to the oxygen abundance, by first accreting solar matter, the amount of accreted material is larger than in those simulations with an initially enriched composition. We vary the mass of the WD (from 0.6 M ⊙ to 1.35 M ⊙) and the composition of the mixed materials. Our results show large enrichments of 7Be in the ejected gases, implying that ONe CNe and CO CNe may be responsible for a significant fraction (∼100 M ⊙) of the Galactic 7Li (∼1000 M ⊙). The production of 22Na and 26Al in CN explosions and the γ-ray emission predicted by our simulations are discussed. The WDs in all our simulations eject less material than they accrete and we predict that the WD is growing in mass as a consequence of the CN outburst. ONe CNe, therefore, may be an important channel for accretion-induced collapse events. *We dedicate this paper to the memory of R. Mark Wagner. Friend, collaborator, exemplary observational astronomer, and contributor to studies of classical novae and transient objects for more than 40 years. He will be missed.

Keywords: Isotopic abundances, Galaxy chemical evolution, Novae, Galaxy abundances, Symbiotic novae, Recurrent novae, Cataclysmic variable stars, Overabundances, Galactic abundances