adsabs/SciX_UAT_keywords huggingface dataset:
Apparent Footpoint Rotation and Writhe of Double Hot Channels in a Solar Flare

We investigate the M6.5 class flare (SOL2015-06-22T18:23) occurring in NOAA Active Region 12371 on 2015 June 22. This eruptive flare is associated with a halo coronal mass ejection with a speed of 1200 km s-1. The 94 Å observations by Atmospheric Image Assembly onboard Solar Dynamics Observatory show that one hot channel first rises up, then forms a kinking structure with negative crossing and erupts, which is followed by the eruption of another kinking hot channel with negative crossing at a similar location between the start and peak times of the flare. Consistent with the standard flare model, footpoint drifting of the two hot channels is observed during the eruption. More interestingly, the two footpoints of the first hot channel continue to drift and display an apparent clockwise rotation after leaving the area of the hook-shaped flare ribbons. This apparent rotation is along the high-Q region of the log Q map derived from the nonlinear force-free field extrapolation. Our analysis suggests that the apparent rotational motion is likely caused by magnetic reconnection between the first hot channel and the surrounding magnetic fields at the high-Q region during the unwrithing process. The unwrithing of the second hot channel is accompanied by a significant slipping motion of its right footpoint.

Keywords: solar x-ray flares; solar extreme ultraviolet emission; solar magnetic reconnection
Shaken or Stirred: The Diffuse Interstellar Medium with Exceptionally High SiO Abundance

Interstellar shocks, a key element of stellar feedback processes, shape the structure of the interstellar medium (ISM) and are essential for the chemistry, thermodynamics, and kinematics of interstellar gas. Powerful, high-velocity shocks are driven by stellar winds, young supernova explosions, more evolved supernova remnants, cloud-cloud collisions, and protostellar outflows, whereas the existence and origin of much-lower-velocity shocks (≲10 km s-1) are not understood. Direct observational evidence for interstellar shocks in diffuse and translucent ISM environments has been especially lacking. We present the most sensitive survey to date of SiO-often considered an unambiguous tracer of interstellar shocks-in absorption, obtained with the Northern Extended Millimeter Array interferometer. We detect SiO in five of eight directions probing diffuse and translucent environments without ongoing star formation. Our results demonstrate that SiO formation in the diffuse ISM (i.e., in the absence of significant star formation and stellar feedback) is more widespread and effective than previously reported. The observed SiO line widths are all ≲4 km s-1, excluding high-velocity shocks as a formation mechanism. Yet, the SiO abundances we detect are mostly 1-2 orders of magnitude higher than those typically assumed in quiescent environments and are often accompanied by other molecular transitions whose column densities cannot be explained with UV-dominated chemical models. Our results challenge the traditional view of SiO production via stellar feedback sources and emphasize the need for observational constraints on the distribution of Si in the gas phase and grain mantles, which are crucial for understanding the physics of grain processing and the diffuse interstellar chemistry.

Keywords: diffuse molecular clouds; interstellar line absorption; shocks
The Broad Line Region and Black Hole Mass of NGC 4151

We present a reanalysis of reverberation mapping data from 2005 for the Seyfert galaxy NGC 4151, supplemented with additional data from the literature to constrain the continuum variations over a significantly longer baseline than the original monitoring program. Modeling of the continuum light curve and the velocity-resolved variations across the Hβ emission line constrains the geometry and kinematics of the broad line region (BLR). The BLR is well described by a very thick disk with similar opening angle (θ o ≈ 57°) and inclination angle (θ i ≈ 58°), suggesting that our sight line toward the innermost central engine skims just above the surface of the BLR. The inclination is consistent with constraints from geometric modeling of the narrow-line region, and the similarity between the inclination and opening angles is intriguing given previous studies of NGC 4151 that suggest BLR gas has been observed temporarily eclipsing the X-ray source. The BLR kinematics are dominated by eccentric bound orbits, with ~10% of the orbits preferring near-circular motions. With the BLR geometry and kinematics constrained, the models provide an independent and direct black hole mass measurement of $\mathrm{log}{M}_{\mathrm{BH}}/{M}_{\odot }={7.22}_{-0.10}^{+0.11}$ or ${M}_{\mathrm{BH}}={1.66}_{-0.34}^{+0.48}\times {10}^{7}$ M ⊙, which is in good agreement with mass measurements from stellar dynamical modeling and gas dynamical modeling. NGC 4151 is one of the few nearby broad-lined Seyferts where the black hole mass may be measured via multiple independent techniques, and it provides an important test case for investigating potential systematics that could affect the black hole mass scales used in the local universe and for high-redshift quasars.

Keywords: seyfert galaxies; supermassive black holes; reverberation mapping
Signatures of Inflowing Gas in Red Geyser Galaxies Hosting Radio Active Galactic Nuclei

We study cool neutral gas traced by NaD absorption in 140 local (z < 0.1) early-type red geyser galaxies. These galaxies show unique signatures in spatially resolved strong line emission maps that have been interpreted as large-scale active galactic nucleus-driven ionized winds. To investigate the possible fuel source for these winds, we examine the abundance and kinematics of cool gas (T ~ 100-1000 K) inferred from Na I D absorption in red geysers and matched control samples drawn from the Sloan Digital Sky Survey IV Mapping Nearby Galaxies at Apache Point Observatory survey. We find that red geysers host greater amounts of NaD-associated material. Substantial cool gas components are detected in more than 50% of red geysers (compared to 25% of the control sample) going up to 78% for radio-detected red geysers. Our key result is that cool gas in red geysers is predominantly infalling. Among our 30 radio-detected red geysers, 86% show receding NaD absorption velocities (with respect to the systemic velocity) between 40 and 50 km s-1. We verify this result by stacking NaD profiles across each sample, which confirms the presence of infalling NaD velocities within red geysers (~40 km s-1) with no velocity offsets detected in the control samples. Interpreting our observations as signatures of inflowing cool neutral clouds, we derive an approximate mass inflow rate of ${\dot{M}}_{\mathrm{in}}\sim 0.1{M}_{\odot }{\mathrm{yr}}^{-1}$ , similar to that expected from minor merging and internal recycling. Some red geysers show much higher rates ( ${\dot{M}}_{\mathrm{in}}\sim 5{M}_{\odot }\ {\mathrm{yr}}^{-1}$ ), which may indicate an ongoing accretion event.

Keywords: galaxy evolution; galaxy quenching; agn host galaxies; galactic winds
Pore Accessibility in Amorphous Solid Water

The porous nature of amorphous solid water (ASW) can significantly effect the chemical evolution of any planetary or astrophysical surface it forms on due to its ability to trap and retain volatiles. The amount of volatiles that can enter an ASW grain or mantle is limited by how interconnected the pores are to each other and to the exterior surface. Previous laboratory studies examined the interconnectivity of ASW pores in thin ASW films relevant to ice mantles on interstellar grains. Here, we investigate to what extent the interconnectivity of pores and subsequent gas absorption properties of ASW change as one moves toward thicker samples (up to ~1019 H2O cm-2 or ~4 μm) more representative of icy material found in the outer solar system. We find that for all film thicknesses studied, the internal pores are accessible from the sample's surface, and the amount of gas needed to fill the pores increases linearly with the ASW column density. This linear relation supports that the interconnectivity to the surface will persist in ices that are much thicker than those we were able to study, suggesting that the amount of contaminant gas trapped within ASW can significantly alter the chemical evolution of a variety of ASW-rich surfaces in the outer solar system.

Keywords: ice porosity; ice physics; ice formation; astrochemistry; solid matter physics; surface ices; laboratory astrophysics
HST/COS Observations of Quasar Outflows in the 500-1050 Å Rest Frame. V. Richness of Physical Diagnostics and Ionization Potential-dependent Velocity Shift in PKS J0352-0711

We analyze absorption troughs from two outflows within PKS J0352-0711 (S1 at -1950 km s-1 and S2 at -3150 km s-1) from spectra taken with Hubble Space Telescope/Cosmic Origins Spectrograph, which cover the diagnostic-rich 585-900 Å rest-frame wavelength range. In S2, for the first time we clearly detect absorption troughs from Ca IV, Ca V, Ca V*, Ca VII*, and Ca VIII*. The column density measurement of Ca V suggests S2 has a super-solar metallicity. Both outflows require at least two ionization phases where the column density of the very high-ionization phase is roughly 15 times larger than the corresponding high-ionization phase. These high column densities and very high-ionization potential ions are similar to X-ray warm absorbers. The two phases of S2 show a unique velocity centroid shift between associated troughs. Through Monte Carlo measurements of the O V* absorption troughs, we determine the electron number density of S2 (fully corroborated by independent measurements from the Ca VII* and Ca VIIi* troughs), yielding a distance of 9 pc and a kinetic luminosity of 2 × 1043 erg s-1. S1 is located farther away at 500 pc from the central source with a kinetic luminosity of 1043 erg s-1.

Keywords: active galactic nuclei; active galaxies; broad-absorption line quasar; quasar absorption line spectroscopy; quasars; agn host galaxies
The Evolution of the Ultraluminous Lyα Luminosity Function over z = 5.7-6.6

Ultraluminous Lyα emitting galaxies (ULLAEs) with $\mathrm{log}L(\mathrm{Ly}\alpha )\gt 43.5$ erg s-1 near the epoch of reionization (z > 5) make up the bright end of the LAE luminosity function (LF) and may provide insight into the process of reionization, including the formation of ionized bubbles around these extreme systems. We present a spectroscopic LF for ULLAEs at z = 5.7. We used data from the HEROES ~45 deg2 Subaru Hyper Suprime-Cam survey, which is centered on the North Ecliptic Pole and has both broadband (grizY) and narrowband (NB816 and NB921) imaging, to select candidate ULLAEs based on a NB816 excess and a strong broadband Lyman break. We spectroscopically observed 17 ULLAE candidates with DEIMOS on Keck II. We confirmed 12 as LAEs at z = 5.7, 9 of which are ULLAEs. The remaining sources are an active galactic nuclei at z = 5.7, an [O III]λ5007 emitter at z = 0.63, a red star, and two spectroscopic nondetections. Using the nine confirmed ULLAEs, we construct a ULLAE LF at z = 5.7. After applying a comprehensive incompleteness correction, we compare our new z = 5.7 LF with our recent z = 6.6 LF and with other LFs from the literature to look for evolution at the ultraluminous end. We find the overall ratio of the z = 5.7 to z = 6.6 ULLAE comoving number densities to be ${1.92}_{-0.71}^{+1.12}$ , which corresponds to an LF offset of ${0.28}_{-0.20}^{+0.20}$ dex.

Keywords: galaxies; emission line galaxies; observational cosmology
Improvement of Digest2 NEO Classification Code-utilizing the Astrometry Data Exchange Standard

We describe enhancements to the digest2 software, a short-arc orbit classifier for heliocentric orbits. Digest2 is primarily used by the Near-Earth Object (NEO) community to flag newly discovered objects for a immediate follow-up and has been a part of NEO discovery process for more than 15 yr. We have updated the solar system population model used to weight the digest2 score according to the 2023 catalog of known solar system orbits and extended the list of mean uncertainties for 140 observatory codes. Moreover, we have added Astrometry Data Exchange Standard (ADES) input format support to digest2, which provides additional information for the astrometry, such as positional uncertainties for each detection. The digest2 code was also extended to read the roving observer astrometric format as well as the ability to compute a new parameter from the provided astrometric uncertainties ( ${RMS}^{\prime} $ ) that can serve as an indicator of in-tracklet curvature when compared with tracklet's great-circle fit rms. Comparison with the previous version of digest2 confirmed the improvement in accuracy of NEO identification and found that using ADES XML input significantly reduces the computation time of the digest2.

Keywords: orbit determination; asteroids; near-earth objects; astronomy data analysis; astrometry; surveys; astronomy software
Beyond Optical Depth: Future Determination of Ionization History from the Cosmic Microwave Background

We explore the fundamental limits to which reionization histories can be constrained using only large-scale cosmic microwave background (CMB) anisotropy measurements. The redshift distribution of the fractional ionization Xe(z) affects the angular distribution of CMB polarization. We project constraints on the reionization history of the universe using low-noise full-sky temperature and E-mode measurements of the CMB. We show that the measured TE power spectrum, ${\hat{C}}_{{\ell }}^{\mathrm{TE}}$ , has roughly one quarter of the constraining power of ${\hat{C}}_{{\ell }}^{\mathrm{EE}}$ on the reionization optical depth τ, and its addition improves the precision on τ by 20% over using ${\hat{C}}_{{\ell }}^{\mathrm{EE}}$ only. We also use a two-step reionization model with an additional high-redshift step, parameterized by an early ionization fraction ${X}_{e}^{\min }$ , and a late reionization step at zre. We find that future high signal-to-noise measurements of the multipoles 10 ≤ ℓ < 20 are especially important for breaking the degeneracy between ${X}_{e}^{\min }$ and zre. In addition, we show that the uncertainties on these parameters determined from a map with sensitivity 10 μK arcmin are less than 5% larger than the uncertainties in the noiseless case, making this noise level a natural target for future large sky area E-mode measurements.

Keywords: cosmic background radiation; reionization; cosmological neutrinos; cosmology
The MACH HI Absorption Survey. I. Physical Conditions of Cold Atomic Gas outside of the Galactic Plane

Tracing the transition between the diffuse atomic interstellar medium and cold, dense gas is crucial for deciphering the star formation cycle in galaxies. Here we present Measuring Absorption by Cold Hydrogen (MACH), a new survey of cold neutral hydrogen (HI) absorption at 21 cm by the Karl G. Jansky Very Large Array. We target 42 bright background sources with 60 < l < 110°, 30 < b < 62°, significantly expanding the sample of publicly available, sensitive 21 cm absorption outside the Galactic plane. With matching 21 cm emission data from the Effelsberg-Bonn HI (EBHIS) Survey, we measure the total column density and cold HI fraction, and quantify the properties of individual HI structures along each sightline via autonomous Gaussian decomposition. Combining the MACH sample with results from recent HI absorption surveys, we produce a robust characterization of the cool atomic medium at high and intermediate Galactic latitudes. We find that MACH HI has significantly smaller column density relative to samples at similar latitudes, and the detected cold HI structures have smaller line widths, temperatures, and turbulent Mach numbers, suggesting that MACH probes a particularly quiescent region. Using all available observations, we compute the cumulative covering fraction (c) of cold HI at local velocities outside the disk: structures with τ > 0.001 are ubiquitous (c ~ 100%), whereas high optical depths (τ > 1) are extremely rare (c ~ 0%).

Keywords: interstellar medium; interstellar absorption; interstellar atomic gas; cold neutral medium; radio astronomy
Nature of Electrostatic Fluctuations in the Terrestrial Magnetosheath

The high cadence plasma, electric, and magnetic field measurements by the Magnetospheric MultiScale spacecraft allow us to explore the near-Earth space plasma with an unprecedented time and spatial resolution, resolving electron-scale structures that naturally emerge from plasma complex dynamics. The formation of small-scale turbulent features is often associated to structured, non-Maxwellian particle velocity distribution functions that are not at thermodynamic equilibrium. Using measurements in the terrestrial magnetosheath, this study focuses on regions presenting bumps in the power spectral density of the parallel electric field at subproton scales. Correspondingly, it is found that the ion velocity distribution functions exhibit beam-like features at nearly the local ion thermal speed. Ion-cyclotron waves in the ion-scale range are frequently observed at the same locations. These observations, supported by numerical simulations, are consistent with the generation of ion-bulk waves that propagate at the ion thermal speed. This represents a new branch of efficient energy transfer at small scales, which may be relevant to weakly collisional astrophysical plasmas.

Keywords: interplanetary turbulence; alfven waves; space plasmas; plasma physics
Hubble Space Telescope Observations of the Old Pulsar PSR J0108-1431

We present results of optical-UV observations of the 200 Myr old rotation-powered radio pulsar J0108-1431 with the Hubble Space Telescope. We found a putative candidate for the far-UV (FUV) pulsar counterpart, with the flux density fν = 9.0 ± 3.2 nJy at λ = 1528 Å. The pulsar was not detected, however, at longer wavelengths, with 3σ upper limits of 52, 37, and 87 nJy at λ = 4326, 3355, and 2366 Å, respectively. Assuming that the pulsar counterpart was indeed detected in FUV, and the previously reported marginal U and B detections with the Very Large Telescope were real, the optical-UV spectrum of the pulsar can be described by a power-law model with a nearly flat fν spectrum. Similar to younger pulsars detected in the optical, the slope of the nonthermal spectrum steepens in the X-ray range. The pulsar's luminosity in the 1500-6000 Å wavelength range, L ∼ 1.2 × 1027(d/210 pc)2 erg s-1, corresponds to a high efficiency of conversion of pulsar rotation energy-loss rate $\dot{E}$ <!-- --> to the optical-UV radiation, $\eta =L/\dot{E}\sim (1\mbox{--}6)\times {10}^{-4}$ <!-- --> , depending on somewhat uncertain values of distance and spectral slope. The brightness temperature of the bulk neutron star surface does not exceed 59,000 K (3σ upper bound), as seen by a distant observer. If we assume that the FUV flux is dominated by a thermal component, then the surface temperature can be in the range of 27,000-55,000 K, Requiring a heating mechanism to operate in old neutron stars. * Based on observations made with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. These observations are associated with program #14249.

Keywords: neutron stars; pulsars
Development of a Deep Learning Model for Inversion of Rotational Coronagraphic Images Into 3D Electron Density

We present, for the first time, a deep learning model that returns the three-dimensional (3D) coronal electron density from coronagraphic images. The intensity of coronagraphic observations arises from the Thomson scattering of photospheric light by the coronal electrons. We use MHD numerical simulations to obtain realistic 3D electron density and construct error-free training sets consisting of input (observation) and target (electron density) images. In the training sets, the input images are directly synthesized from the target 3D electron density by applying the Thomson scattering theory. The input and target images are in the form of latitude-longitude maps given at a radius, often referred to as synoptic maps. Using synoptic maps reduces a tomographic method to an image translation problem. We use pix2pixHD, one of the well-established supervised image translation methods and develop models for six selected heights: 2.0, 2.2, 2.5, 4.0, 6.0, and 12.0 solar radii. All six models have similar performance and the mean absolute percent error of the generated density images is less than 7% with respect to the ground-truth simulated data sets.

Keywords: solar corona; coronagraphic imaging; neural networks
Infrared Coronal Line Emission during the 2010 Outburst of the Recurrent Nova U Scorpii

Infrared spectroscopy of the recurrent nova U Scorpii from 14.2 days after its 2010 outburst reveals two very strong infrared coronal lines: [Si X] at 1.4305 μm and [Al IX] at 2.0400 μm. Taken together with the detection of coronal lines in the 2022 outburst, this suggests that coronal line emission from U Sco may be a regular, if previously under-observed, occurrence. The strength of the two coronal lines relative the H I emission, and the surprising absence of several commonly seen coronal lines, including some that form under similar conditions as the [Si X] and [Al IX] features, are discussed.

Keywords: recurrent novae
Universal Transition Diagram from Dormant to Actively Accreting Supermassive Black Holes

The vast majority of supermassive black holes (SMBHs) in the local universe exhibit levels of activity much lower than those expected from gas supplying rates onto the galactic nuclei, and only a small fraction of silent SMBHs can turn into active galactic nuclei. Revisiting observational data of very nearby SMBHs whose gravitational spheres of influence are spatially reached by the Chandra X-ray satellite, we find that the level of BH activity drastically increases from the quiescent phase when the inflow rate outside of the BH influence radius is higher than 0.1% of the Eddington accretion rate. We also show that the relation between the nuclear luminosity and gas accretion rate from the BH influence radius measured from X-ray observations is well described by the universal state transition of accreting SMBHs, as predicted by recent hydrodynamical simulations with radiative cooling and BH feedback. After the state transition, young massive stars should form naturally in the nucleus, as observed in the case of the nearest SMBH, Sagittarius A*, which is currently quiescent but was recently active.

Keywords: galaxy nuclei; seyfert galaxies; supermassive black holes