Sazuna/UAT_keywords huggingface dataset:
Relationship of Transport Coefficients with Statistical Quantities of Charged Particles. In previous studies, a general spatial transport equation was derived from the Fokker-Planck equation. The latter equation contains an infinite number of spatial derivative terms T  n  = κ  nz ∂ n  F/∂z  n  with n = 1, 2, 3, ⋯ . Due to the complexity of the general equation, some simplified equations with finitely many spatial derivative terms have been used by astrophysical researches, e.g., the diffusion equation, the hyperdiffusion equation, subdiffusion transport equation, etc. In this paper, the simplified transport equations with the spatial derivative terms up to the first, second, third, fourth, and fifth order are listed, and their transport coefficient formulas are derived, respectively. We find that most of the transport coefficients are determined by the corresponding statistical quantities. In addition, we find that the well-known statistical quantities, the skewness ${ \mathcal S }$ and the kurtosis ${ \mathcal K }$ , are determined by some transport coefficients. The results can help one to use various transport coefficients determined by the statistical quantities, including many that are relatively newfound in this paper, to study charged particle parallel transport processes.

Keywords: Interplanetary turbulence, Interplanetary physics, Interplanetary magnetic fields
Stream Fanning and Bifurcations: Observable Signatures of Resonances in Stellar Stream Morphology. Recent observations have revealed a trove of unexpected morphological features in many of the Milky Way's stellar streams. Explanations for such features include time-dependent deformations of the Galactic gravitational potential, local disruptions induced by dark matter substructure, and special configurations of the streams' progenitors. In this paper, we study how these morphologies can also arise in certain static, nonspherical gravitational potentials that host a subset of resonantly trapped orbit families. The transitions, or separatrices, between these orbit families mark abrupt discontinuities in the orbital structure of the potential. We develop a novel numerical approach for measuring the libration frequencies of resonant and near-resonant orbits and apply it to study the evolution of stellar streams on these orbits. We reveal two distinct morphological features that arise in streams on near-resonant orbits: fans, which come about due to a large spread in the libration frequencies near a separatrix, and bifurcations, which arise when a separatrix splits the orbital distribution of the stellar stream between two (or more) distinct orbit families. We demonstrate that these effects can arise in some Milky Way streams for certain choices of the dark matter halo potential and discuss how this might be used to probe and constrain the global shape of the Milky Way's gravitational potential.

Keywords: Milky Way dark matter halo, Milky Way dynamics, Stellar streams, Orbital resonances
Internal and External Alignment of Carbonaceous Grains within the Radiative Torque Paradigm. We study the internal and external alignment of carbonaceous grains in the interstellar medium (ISM) within the Radiative Torque (RAT) paradigm. For internal alignment (IA), we find that hydrogenated amorphous carbon (HAC) grains having nuclear paramagnetism due to hydrogen protons have efficient nuclear relaxation, whereas both HAC and graphite grains can have efficient inelastic relaxation at both low-J and high-J attractors. For external alignment, HAC and pure graphite grains can align with the radiation direction (k-RAT) at low-J attractors but cannot have stable alignment at high-J attractors due to the suppression of radiative precession. However, HAC grains can align with the magnetic field (B-RAT) at high-J attractors due to fast Larmor precession compared to gas collisions. For HAC grains drifting through the ISM, they can align along the induced electric field (E-RAT) at low-J attractors due to the fast electric precession and only small HAC grains can align at high-J attractors. Nuclear paramagnetic relaxation is inefficient for HAC due to the suppression of nuclear susceptibility. We then study the alignment of carbon dust in the envelope of a C-rich Asymptotic Giant Branch star (IRC+10216) and find that grains aligned at low-J attractors may occur via k-RAT with the wrong IA in the inner region but via B-RAT in the outer region. However, grains aligned at high-J attractors have the right IA alignment via k-RAT due to efficient inelastic relaxation. The polarization pattern observed toward IRC+10216 by SOFIA/HAWC+ can be reproduced when only grains at low-J attractors are present due to the removal of grains at high-J attractors by the RAT disruption.

Keywords: Dust composition, Evolved stars, Astrophysical dust processes, Starlight polarization, Interstellar dust processes, Circumstellar dust
Dissipative Instability of Magnetohydrodynamic Sausage Waves in a Compressional Cylindrical Plasma: Effect of Flow Shear and Viscosity Shear. The shear flow influences the stability of magnetohydrodynamic (MHD) waves. In the presence of a dissipation mechanism, flow shear may induce an MHD wave instability below the threshold of the Kelvin-Helmholtz instability, which is called dissipative instability. This phenomenon is also called negative energy wave instability because it is closely related to the backward wave, which has negative wave energy. Considering viscosity as a dissipation mechanism, we derive an analytical dispersion relation for the slow sausage modes in a straight cylinder with a discontinuous boundary. It is assumed that the steady flow is inside and dynamic and bulk viscosities are outside the circular flux tube under photospheric condition. When the two viscosities are weak, it is found that for the slow surface mode, the growth rate is proportional to the axial wavenumber and flow shear, consistent within the incompressible limit. For a slow body mode, the growth rate has a peak at a certain axial wavenumber, and its order of magnitude is similar to surface mode. The linear relationship between the growth rate and the dynamic viscosity established in the incompressible limit develops nonlinearly when the flow shear and/or the two viscosities are sufficiently strong.

Keywords: Solar oscillations, Magnetohydrodynamics, Solar photosphere
Magnetic Field Information in the Near-ultraviolet Fe II Lines of the CLASP2 Space Experiment. We investigate theoretically the circular polarization signals induced by the Zeeman effect in the Fe II lines of the 279.3-280.7 nm spectral range of the CLASP2 space experiment and their suitability to infer solar magnetic fields. To this end, we use a comprehensive Fe II atomic model to solve the problem of the generation and transfer of polarized radiation in semiempirical models of the solar atmosphere, comparing the region of formation of the Fe II spectral lines with those of the Mg II h and k and the Mn I resonance lines. These are present in the same near-ultraviolet (near-UV) spectral region and allowed the mapping of the longitudinal component of the magnetic field (B L) through several layers of the solar chromosphere in an active region plage. We compare our synthetic intensity profiles with observations from the IRIS and CLASP2 missions, proving the suitability of our model atom to characterize these Fe II spectral lines. The CLASP2 observations show two Fe II spectral lines at 279.79 and 280.66 nm with significant circular polarization signals. We demonstrate the suitability of the weak-field approximation applied to the Stokes I and V profiles of these Fe II lines to infer B L in the plage atmosphere. We conclude that the near-UV spectral region of CLASP2 allows us to determine B L from the upper photosphere to the top of the chromosphere of active region plages.

Keywords: Solar photosphere, Solar chromosphere, Spectropolarimetry, Solar magnetic fields
Is It Possible to Measure the Lense-Thirring Orbital Shifts of the Short-period S Star S4716 Orbiting Sgr A*?. The maximal values of the general relativistic Lense-Thirring (LT) orbital shifts ΔI LT, ΔΩLT, and Δω LT of the inclination I, the longitude of the ascending node Ω, and the perinigricon ω, respectively, of the recently discovered star S4716, which has the shortest orbital period $\left({P}_{{\rm{b}}}=4.02\,\mathrm{yr}\right)$ of all the S stars that orbit the supermassive black hole (SMBH) in Sgr A*, are of the order of ≃5-16 arcseconds per revolution $\left({}^{{\prime\prime} }\,{\mathrm{rev}}^{-1}\right)$ . Given the current error σ  ω  = 0.°02 in determining ω, which is the most accurate orbital parameter of S4716 among all those affected by the SMBH's gravitomagnetic field through its angular momentum J •, about 48 yr would be needed to reduce σ  ω  to ≃10% of the cumulative LT perinigricon shift over the same time span. Measuring ΔI LT and ΔΩLT to the same level of accuracy would take much longer. Instead, after just 16 yr, a percent measurement of the larger gravitoelectric (GE) Schwarzschild-like perinigricon shift Δω GE, which depends only on the SMBH's mass M •, would be possible. On the other hand, the uncertainties in the physical and orbital parameters entering Δω GE would cause a huge systematic bias of Δω LT itself. The SMBH's quadrupole mass moment ${Q}_{2}^{\bullet }$ induces orbital shifts as little as ≃0.01-0.05″ rev-1.

Keywords: General relativity, Orbital elements, Kerr black holes
ALMA Reveals Hidden Morphologies in the Molecular Envelope of VY Canis Majoris. The J = 2 → 1 transition of CO near 230 GHz and the J = 3 → 2 line of HCN at 265 GHz have been imaged in the envelope of the red hypergiant star, VY Canis Majoris (VY CMa), using the Atacama Large Millimeter Array (ALMA) with angular resolutions 0.″2-1.″5; single-dish data were added to provide sensitivity up to 30″. These images reveal a far more complex envelope, with previously unseen outflows extending 4″-9″ from the star. These new structures include an arc-like outflow with an angular separation of ~9″ northeast from the stellar position ("NE Arc"), twin fingerlike features approximately 4″ to the north/northeast ("NE Extension"), and a roughly spherical region observed ~7″ E of the star ("E Bubble"). The NE Arc appears to be decelerating from base (V LSR ~ 7 km s-1) to tip (V LSR ~ 18 km s-1), while the NE Extension is blueshifted with V LSR ~ -7 km s-1. Among the new features, HCN is only detected in the NE Arc. In addition, known structures Arc 1, Arc 2, and NW Arc, as well as other features closer to the star, are closely replicated in CO, suggesting that the gas and dust are well mixed. The CO spectra are consistent with the kinematic picture of VY CMa derived from HST data. Arc 2, however, has added complexity. Preliminary results from CO suggest 12C/13C ~ 22-38 across the envelope. The additional presence of at least three major episodic mass ejection events significantly broadens the current perspective of the envelope structure and mass-loss history of VY CMa.

Keywords: Circumstellar envelopes, Millimeter astronomy, Stellar mass loss, Stellar winds, Hypergiant stars, Stellar evolution
Flyby Galaxy Encounters with Multiple Black Holes Produce Star-forming Linear Features. We look for simulated star-forming linear features such as the one recently discovered by van Dokkum et al. in the cosmological hydrodynamical simulation ASTRID. Among the runaway black holes in ASTRID, none are able to produce clear star-forming wakes. Meanwhile, flyby encounters, typically involving a compact galaxy (with a central black hole) and a star-forming galaxy (with a duo of black holes), reproduce remarkably well many of the key properties (length and linearity, recent star formation, etc.) of the observed star-forming linear feature. We predict that the feature will persist for approximately 100 Myr in such a system and hence constitute a rare event. The feature contains a partly stripped galaxy (with M gal = 109-1010 M ⊙) and a dual black hole system (M BH = 105-107 M ⊙) in its brightest knot. The X-ray emission from AGN in the knot should be detectable in such systems. After 100-200 Myr from the first flyby, the galaxies merge, leaving behind a triple black hole system in a (still) actively star-forming early-type remnant of mass ~5 × 1010 M ⊙. Follow-up JWST observations may be key for revealing the nature of these linear features by potentially detecting the older stellar populations constituting the bright knot. Confirmation of such detections may therefore help discriminate a flyby encounter from a massive black hole wake to reveal the origin of such features.

Keywords: Supermassive black holes, Computational methods, Astronomy data analysis
Magnitude Estimates for the Carrington Flare in 1859 September: As Seen from the Original Records. The Carrington flare in 1859 September is a benchmark, as the earliest reported solar flare and as an event with one of the greatest terrestrial impacts. To date, no rigorous estimate of the energy of this flare has been made on the basis of the only direct observation available, its white-light emission. Here, we exploit the historical observations to obtain a magnitude estimate and express it in terms of its GOES soft X-ray class. From Carrington's original drawings, we estimated the area of the white-light flaring region to be 116 ± 25 msh. Carrington's account allows us to estimate the flare blackbody brightness temperature as ≈8800-10,900 K, given the most plausible interpretation of the reported flare brightness. This leads to an unprecedented class estimate of ≈X80 (X46-X126), on the modern revised GOES scale (a factor 1.43 higher than the traditional one). This substantially exceeds earlier estimates but is based on an explicit interpretation of Carrington's description. We also describe an alternative but less plausible estimation of the flare brightness, as adopted previously, to obtain a class estimate of ≈X14 (X9-X19). This now-deprecated scenario gives an estimate similar to that of with those of directly observed modern great flares. Approximations with "equivalent area," based on the Hinode observations, lead to comparable magnitudes and approve our estimates, though with a larger uncertainty range. We note that our preferred estimate is higher than the currently used value of X64.4 ± 7.2 (revised) based on indirect geomagnetic measurements.

Keywords: Solar flares, Space weather, Sunspots, Solar active regions, Solar white-light flares, Solar x-ray flares, Solar storm
Hidden Little Monsters: Spectroscopic Identification of Low-mass, Broad-line AGNs at z &gt; 5 with CEERS. We report on the discovery of two low-luminosity, broad-line active galactic nuclei (AGNs) at z &gt; 5 identified using JWST NIRSpec spectroscopy from the Cosmic Evolution Early Release Science (CEERS) survey. We detect broad Hα emission in the spectra of both sources, with FWHM of 2060 ± 290 km s‑1 and 1800 ± 200 km s‑1, resulting in virial black hole (BH) masses that are 1–2 dex below those of existing samples of luminous quasars at z &gt; 5. The first source, CEERS 2782 at z = 5.242, is 2–3 dex fainter than known quasars at similar redshifts and was previously identified as a candidate low-luminosity AGN based on its morphology and rest-frame optical spectral energy distribution (SED). We measure a BH mass of M BH = (1.3 ± 0.4) × 107 M ⊙, confirming that this AGN is powered by the least massive BH known in the Universe at the end of cosmic reionization. The second source, CEERS 746 at z = 5.624, is inferred to be a heavily obscured, broad-line AGN caught in a transition phase between a dust-obscured starburst and an unobscured quasar. We estimate its BH mass to be in the range of M BH ≃ (0.9–4.7) × 107 M ⊙, depending on the level of dust obscuration assumed. We perform SED fitting to derive host stellar masses, M ⋆, allowing us to place constraints on the BH–galaxy mass relationship in the lowest mass range yet probed in the early Universe. The M BH/M ⋆ ratio for CEERS 2782, in particular, is consistent with or higher than the empirical relationship seen in massive galaxies at z = 0. We examine the narrow emission line ratios of both sources and find that their location on the BPT and OHNO diagrams is consistent with model predictions for moderately low metallicity AGNs with Z/Z ⊙ ≃ 0.2–0.4. The spectroscopic identification of low-luminosity, broad-line AGNs at z &gt; 5 with M BH ≃ 107 M ⊙ demonstrates the capability of JWST to push BH masses closer to the range predicted for the BH seed population and provides a unique opportunity to study the early stages of BH–galaxy assembly.

Keywords: Supermassive black holes, Active galactic nuclei, High-redshift galaxies, Quasars
Extreme Variability in a Long-duration Gamma-Ray Burst Associated with a Kilonova. The recent discovery of a kilonova from the long-duration gamma-ray burst (GRB) GRB 211211A challenges classification schemes based on temporal information alone. Gamma-ray properties of GRB 211211A reveal an extreme event, which stands out among both short and long GRBs. We find very short variations (few milliseconds) in the lightcurve of GRB 211211A and estimate ~1000 for the Lorentz factor of the outflow. We discuss the relevance of the short variations in identifying similar long GRBs resulting from compact mergers. Our findings indicate that in future gravitational-wave follow-up campaigns, some long-duration GRBs should be treated as possible strong gravitational-wave counterparts.

Keywords: Gamma-ray bursts, Gamma-rays
Ultracool Dwarfs Observed with the Spitzer Infrared Spectrograph: Equatorial Latitudes in L Dwarf Atmospheres Are Cloudier. We report direct observational evidence for a latitudinal dependence of dust cloud opacity in ultracool dwarfs, indicating that equatorial latitudes are cloudier than polar latitudes. These results are based on a strong positive correlation between the viewing geometry and the mid-infrared silicate absorption strength in mid-L dwarfs using mid-infrared spectra from the Spitzer Space Telescope and spin axis inclination measurements from available information in the literature. We confirmed that the infrared color anomalies of L dwarfs positively correlate with dust cloud opacity and viewing geometry, where redder objects are inclined equator-on and exhibit more opaque dust clouds, while dwarfs viewed at higher latitudes and with more transparent clouds are bluer. These results show the relevance of viewing geometry to explain the appearance of brown dwarfs and provide insight into the spectral diversity observed in substellar and planetary atmospheres. We also find a hint that dust clouds at similar latitudes may have higher opacity in low-surface gravity dwarfs than in higher-gravity objects.

Keywords: Brown dwarfs, L dwarfs, Solar system gas giant planets, Planetary atmospheres, Extrasolar gaseous giant planets, Exoplanet atmospheres
The FRB 20190520B Sight Line Intersects Foreground Galaxy Clusters. The repeating fast radio burst FRB 20190520B is an anomaly of the FRB population thanks to its high dispersion measure (DM = 1205 pc cm-3) despite its low redshift of z frb = 0.241. This excess has been attributed to a large host contribution of DMhost ≈ 900 pc cm-3, far larger than any other known FRB. In this paper, we describe spectroscopic observations of the FRB 20190520B field obtained as part of the FLIMFLAM survey, which yielded 701 galaxy redshifts in the field. We find multiple foreground galaxy groups and clusters, for which we then estimated halo masses by comparing their richness with numerical simulations. We discover two separate M halo &gt; 1014 M ⊙ galaxy clusters at z = 0.1867 and 0.2170 that are directly intersected by the FRB sight line within their characteristic halo radius r 200. Subtracting off their estimated DM contributions, as well that of the diffuse intergalactic medium, we estimate a host contribution of ${{\rm{D}}{\rm{M}}}_{{\rm{h}}{\rm{o}}{\rm{s}}{\rm{t}}}={430}_{-220}^{+140}$ or ${280}_{-170}^{+140}\,{\rm{p}}{\rm{c}}\,{{\rm{c}}{\rm{m}}}^{-3}$ (observed frame), depending on whether we assume that the halo gas extends to r 200 or 2 × r 200. This significantly smaller DMhost-no longer the largest known value-is now consistent with Hα emission measures of the host galaxy without invoking unusually high gas temperatures. Combined with the observed FRB scattering timescale, we estimate the turbulent fluctuation and geometric amplification factor of the scattering layer to be $\widetilde{F}G\approx 4.5\mbox{--}11{({\mathrm{pc}}^{2}\,\mathrm{km})}^{-1/3}$ , suggesting that most of the gas is close to the FRB host. This result illustrates the importance of incorporating foreground data for FRB analyses both for understanding the nature of FRBs and to realize their potential as a cosmological probe.

Keywords: Redshift surveys, Intergalactic gas, Circumgalactic medium, Radio transient sources
S<SUB>8</SUB> Tension in the Context of Dark Matter-Baryon Scattering. We explore an interacting dark matter (IDM) model that allows for a fraction of dark matter (DM) to undergo velocity-independent scattering with baryons. In this scenario, structure on small scales is suppressed relative to the cold DM scenario. Using the effective field theory of large-scale structure, we perform the first systematic analysis of BOSS full-shape galaxy clustering data for the IDM scenario, and we find that this model ameliorates the S 8 tension between large-scale structure and Planck data. Adding the S 8 prior from the Dark Energy Survey (DES) to our analysis further leads to a mild ~3σ preference for a nonvanishing DM-baryon scattering cross section, assuming ~10% of DM is interacting and has a particle mass of 1 MeV. This result produces a modest ~20% suppression of the linear power at k ≲ 1 h Mpc-1, consistent with other small-scale structure observations. Similar scale-dependent power suppression was previously shown to have the potential to resolve S 8 tension between cosmological data sets. The validity of the specific IDM model explored here will be critically tested with upcoming galaxy surveys at the interaction level needed to alleviate the S 8 tension.

Keywords: Cosmology, Large-scale structure of the universe, Cosmic microwave background radiation, Dark matter, Redshift surveys, Particle astrophysics
Geometry and Kinematics of a Dancing Milky Way: Unveiling the Precession and Inclination Variation across the Galactic Plane via Open Clusters. This Letter presents a study of the geometry and motion of the Galactic disk using open clusters in the Gaia era. The findings suggest that the inclination θ  i  of the Galactic disk increases gradually from the inner to the outer disk, with a shift in orientation at the Galactocentric radius of approximately 6 ± 1 kpc. Furthermore, this study brings forth the revelation that the mid-plane of the Milky Way may not possess a stationary or fixed position. A plausible explanation is that the inclined orbits of celestial bodies within our Galaxy exhibit a consistent pattern of elliptical shapes, deviating from perfect circularity; however, more observations are needed to confirm this. An analysis of the vertical motion along the Galactocentric radius reveals that the disk has warped with precession and that the line of node shifts at different radii, aligning with the results from the classical Cepheids. Although there is uncertainty for precession/peculiar motion in solar orbit, after considering the uncertainty, the study derives a median value of ${\dot{\phi }}_{\mathrm{LON}}$ = 6.8 km s-1 kpc-1 in the Galaxy. This value for the derived precession in the outer disk is lower than those in the literature due to the systematic motion in solar orbit (θ  i = 0.°6). The study also finds that the inclinational variation of the disk is significant and can cause systematic motion, with the variation rate ${\dot{\theta }}_{i}$ decreasing along the Galactic radius with a slope of -8.9 μas yr-1 kpc-1. Moreover, the derived ${\dot{\theta }}_{i}$ in solar orbit is 59.1 ± 11.2sample ± 7.7 ${}_{{V}_{Z\odot }}$ μas yr-1, which makes it observable for high-precision astrometry.

Keywords: Galaxy structure, Galaxy disks, Open star clusters, Milky Way Galaxy, Galaxies