adsabs/SciX_UAT_keywords huggingface dataset:
When Hot Meets Cold: Post-flare Coronal Rain

Most solar flares demonstrate a prolonged, hour-long post-flare (or gradual) phase, characterized by arcade-like, post-flare loops (PFLs) visible in many extreme ultraviolet (EUV) passbands. These coronal loops are filled with hot (~30 MK) and dense plasma that evaporated from the chromosphere during the impulsive phase of the flare, and they very gradually recover to normal coronal density and temperature conditions. During this gradual cooling down to ~1 MK regimes, much cooler (~0.01 MK) and denser coronal rain is frequently observed inside PFLs. Understanding PFL dynamics in this long-duration, gradual phase is crucial to the entire corona-chromosphere mass and energy cycle. Here we report a simulation in which a solar flare evolves from pre-flare, over the impulsive phase all the way into its gradual phase, which successfully reproduces post-flare coronal rain. This rain results from catastrophic cooling caused by thermal instability, and we analyze the entire mass and energy budget evolution driving this sudden condensation phenomenon. We find that the runaway cooling and rain formation also induces the appearance of dark post-flare loop systems, as observed in EUV channels. We confirm and augment earlier observational findings, suggesting that thermal conduction and radiative losses alternately dominate the cooling of PFLs.

Keywords: solar physics; solar flares; magnetohydrodynamical simulations
Discovery of Thionylimide, HNSO, in Space: The first N-, S-, and O-bearing Interstellar Molecule

We present the first detection in space of thionylimide (HNSO) toward the Galactic center molecular cloud G + 0.693-0.027, thanks to the superb sensitivity of an ultradeep molecular line survey carried out with the Yebes 40 m and IRAM 30 m telescopes. This molecule is the first species detected in the interstellar medium containing, simultaneously, N, S, and O. We have identified numerous K a = 0, 1, and 2 transitions belonging to HNSO covering from J up = 2 to J up =10, including several completely unblended features. We derive a molecular column density of N = (8 ± 1)×1013 cm‑2, yielding a fractional abundance relative to H2 of ∼6 × 10‑10, which is about ∼37 and ∼4.8 times less abundant than SO and SO2, respectively. Although there are still many unknowns in the interstellar chemistry of NSO-bearing molecules, we propose that HNSO is likely formed through the reaction of the NSO radical and atomic H on the surface of icy grains, with alternative routes also deserving exploration. Finally, HNSO appears as a promising link between N, S, and O interstellar chemistry, and its discovery paves the route to the detection of a new family of molecules in space.

Keywords: interstellar molecules; interstellar clouds; galactic center; spectral line identification; astrochemistry
Spectroastrometric Reverberation Mapping of Broad-line Regions

Spectroastrometry measures source astrometry as a function of wavelength/velocity. Reverberations of spectroastrometric signals naturally arise in broad-line regions (BLRs) of active galactic nuclei (AGNs) as a result of the continuum variations that drive responses of the broad emission lines with time delays. Such signals provide a new diagnostic for mapping BLR kinematics and geometry, complementary to the traditional intensity reverberation mapping (RM) technique. We present a generic mathematical formalism for spectroastrometric RM and show that under realistic parameters of a phenomenological BLR model, the spectroastrometric reverberation signals vary on a level of several to tens of microarcseconds, depending on the BLR size, continuum variability, and angular-size distance. We also derive the analytical expressions of spectroastrometric RM for an inclined ring-like BLR. We develop a Bayesian framework with a sophisticated Monte Carlo sampling technique to analyze spectroastrometric data and infer the BLR properties, including the central black hole mass and angular-size distance. We demonstrate the potential of spectroastrometric RM in spatially resolving BLR kinematics and geometry through a suite of simulation tests. The application to realistic observation data of 3C 273 obtains tentative, but enlightening results, reinforcing the practical feasibility of conducting spectroastrometric RM experiments on bright AGNs with the operating Very Large Telescope Interferometer as well as possibly with the planned next-generation 30 m class telescopes.

Keywords: astrometry; reverberation mapping; supermassive black holes; active galactic nuclei
Hunting Gamma-Ray-emitting FR0 Radio Galaxies in Wide-field Sky Surveys

The latest entry in the jetted active galactic nuclei (AGN) family is the Fanaroff-Riley type 0 (FR0) radio galaxies. They share several observational characteristics, e.g., nuclear emission and host galaxy morphology, with FR I sources; however, they lack extended, kiloparsec-scale radio structures, which are the defining features of canonical FR I and II sources. Here we report the identification of seven γ-ray-emitting AGN as FR0 radio sources by utilizing the high-quality observations delivered by ongoing multiwavelength wide-field sky surveys, e.g., Very Large Array Sky Survey. The broadband observational properties of these objects are found to be similar to their γ-ray undetected counterparts. In the γ-ray band, FR0 radio galaxies exhibit spectral features similar to more common FR I and II radio galaxies, indicating a common γ-ray production mechanism and the presence of misaligned jets. Although the parsec-scale radio structure of FR0s generally exhibits a wide range, with about half having emission on opposite sides of the core, the γ-ray-detected FR0s tend to have dominant cores with core-jet structures. We conclude that dedicated, high-resolution observations are needed to unravel the origin of relativistic jets in this enigmatic class of faint yet numerous population of compact radio sources.

Keywords: fanaroff-riley radio galaxies; bl lacertae objects; relativistic jets; gamma-ray sources
Finding Direct-collapse Black Holes at Birth

Direct-collapse black holes (DCBHs) are currently one of the leading contenders for the origins of the first quasars in the universe, over 300 of which have now been found at z > 6. But the birth of a DCBH in an atomically cooling halo does not by itself guarantee it will become a quasar by z ∼ 7, the halo must also be located in cold accretion flows or later merge with a series of other gas-rich halos capable of fueling the BH's rapid growth. Here, we present near-infrared luminosities for DCBHs born in cold accretion flows in which they are destined to grow to 109 ${M}_{\odot }$ by z ∼ 7. Our observables, which are derived from cosmological simulations with radiation hydrodynamics with Enzo, reveal that DCBHs could be found by the James Webb Space Telescope at z ≲ 20 and strongly lensed DCBHs might be found in future wide-field surveys by Euclid and the Wide-Field Infrared Space Telescope at z ≲ 15.

Keywords: high-redshift galaxies; intermediate-mass black holes; population iii stars; supermassive black holes; primordial galaxies; quasars
Interplanetary Coronal Mass Ejections as the Driver of Non-recurrent Forbush Decreases

Interplanetary coronal mass ejections (ICMEs) are the counterparts of coronal mass ejections (CMEs) that extend in the interplanetary (IP) space and interact with the underlying solar wind (SW). ICMEs and their corresponding shocks can sweep out galactic cosmic rays (GCRs) and thus modulate their intensity, resulting in non-recurrent Forbush decreases (FDs). In this work, we selected all FDs that were associated with a sudden storm commencement (SSC) at Earth, and a solar driver (e.g., CME) was clearly identified as the ICME's source. We introduce and employ the tH parameter, which is the time delay (in hours) of the maximum strength of the interplanetary magnetic field from the FD onset (as is marked via the SSC), and consequently derive three groups of FD events (I.e., the early, medium, and late ones). For each of these we examine the mean characteristics of the FDs and the associated IP variations per group, as well as the resulting correlations. In addition, we demonstrate the outputs of a superposed epoch analysis, which led to an average time profile of the resulting FDs and the corresponding IP variations, per group. Finally, we interpret our results based on the theoretical expectations for the FD phenomenon. We find that both the shock sheath and the ejecta are necessary for deep GCR depressions and that the FD amplitude (A0) is larger for faster-propagating ICMEs. Additionally, we note the importance of the turbulent shock-sheath region across all groups. Finally, we present empirical relations connecting A0 to SW properties.

Keywords: solar coronal mass ejections; galactic cosmic rays; solar wind
Global Extinction: Gemini North and South GMOS Combined Photometry Relative to the Gaia Catalog, and Long-term Atmospheric Change

Effects of long-term atmospheric change were looked for in photometry employing Gemini North and South twin Multi-Object Spectrograph (GMOS-N and GMOS-S) archival data. The whole GMOS imaging database, beginning from 2003, was compared against the all-sky Gaia object catalog, yielding ~106 Sloan $r^{\prime} $ -filter samples, ending in 2021. These were combined with reported sky and meteorological conditions, and versus a simple model of the atmosphere plus cloud together with simulated throughputs. One exceptionally extincted episode in 2009 is seen, as is a trend (similar at both sites) of about 2 mmag worsening attenuation per decade. This is consistent with solar-radiance transmissivity records going back over six decades, aerosol density measurements, and more than 0.2°C/decade rise in air temperature, which has implications for the calibration of historic data sets or future surveys.

Keywords: astronomical instrumentation; astronomical methods; astronomical site protection
The SOFIA FEEDBACK Legacy Survey Dynamics and Mass Ejection in the Bipolar H II Region RCW 36

We present [C II] 158 μm and [O I] 63 μm observations of the bipolar H II region RCW 36 in the Vela C molecular cloud, obtained within the SOFIA legacy project FEEDBACK, which is complemented with APEX 12/13CO (3-2) and Chandra X-ray (0.5-7 keV) data. This shows that the molecular ring, forming the waist of the bipolar nebula, expands with a velocity of 1-1.9 km s-1. We also observe an increased line width in the ring, indicating that turbulence is driven by energy injection from the stellar feedback. The bipolar cavity hosts blueshifted expanding [C II] shells at 5.2 ± 0.5 ± 0.5 km s-1 (statistical and systematic uncertainty), which indicates that expansion out of the dense gas happens nonuniformly and that the observed bipolar phase might be relatively short (~0.2 Myr). The X-ray observations show diffuse emission that traces a hot plasma, created by stellar winds, in and around RCW 36. At least 50% of the stellar wind energy is missing in RCW 36. This is likely due to leakage that is clearing even larger cavities around the bipolar RCW 36 region. Lastly, the cavities host high-velocity wings in [C II], which indicates relatively high mass ejection rates (~5 × 10-4 M ⊙ yr-1). This could be driven by stellar winds and/or radiation but remains difficult to constrain. This local mass ejection, which can remove all mass within 1 pc of RCW 36 in 1-2 Myr, and the large-scale clearing of ambient gas in the Vela C cloud indicate that stellar feedback plays a significant role in suppressing the star formation efficiency.

Keywords: h ii regions
Voluminous Silica Precipitated from Martian Waters during Late-stage Aqueous Alteration

Mars' transition from an early "warm and wet" to a "cold and dry" environment left fingerprints on the geological record of fluvial activity on Mars. The morphological and mineralogical observations of aqueous activity provided varying constraints on the condition and duration of liquid water on the Martian surface. In this study, we surveyed the mineralogy of Martian alluvial fans and deltas and investigated the hydrated silica-bearing deposits associated with some of these landforms. Using CRISM data, we identified 35 locations across Mars with hydrated silica in proximity to fans/deltas, where the spectral characteristics are consistent with immature or dehydrated opal-A. In a few stepped fans/deltas, we find hydrated silica occurs within the bulk fan deposits and form sedimentary layers correlated with elevation. Meanwhile, in the older fans/deltas, silica mostly occurs at distal locations, and the relation to primary sedimentary deposits is more complex. We propose that the hydrated silica-bearing deposits in stepped fans/deltas likely formed authigenically from Martian surface waters, mainly during the Late Hesperian and Early Amazonian. These silica-bearing deposits could be a tracer for the temperature or duration of water involved in the formation of these deposits, given more precise and detailed observations of the sedimentary context, accessory minerals, the concentration of hydrated silica, and sediment-to-water ratio. Therefore, we consider that silica-bearing deposits should be among the most critical samples to investigate for future Mars missions, which are accessible in the landing sites of Mars 2020 and ExoMars 2022 missions.

Keywords: mars; planetary surfaces; surface composition; hydrosphere; planetary structure
Are Radio Minihalos Confined by Cold Fronts in Galaxy Clusters? Minihalos and Large-scale Sloshing in A3444 and MS 1455.0+2232

We present radio and X-ray studies of A3444 and MS1455.0+2232, two galaxy clusters with radio minihalos in their cool cores. A3444 is imaged using the Giant Metrewave Radio Telescope (GMRT) at 333, 607, and 1300 MHz and the Very Large Array at 1435 MHz. Most of the minihalo is contained within r < 120 kpc, but a fainter extension, stretching out to 380 kpc southwest of the center, is detected at 607 MHz. Using Chandra, we detect four X-ray sloshing cold fronts: three in the cool core at r = 60, 120, and 230 kpc, and a fourth one at r = 400 kpc-in the region of the southwestern radio extension-suggesting that the intracluster medium (ICM) is sloshing on a cluster-wide scale. The radio emission is contained within the envelope defined by these fronts. We also analyzed archival 383 MHz GMRT and Chandra observations of MS 1455.0+2232, which exhibits a known minihalo with its bright part delineated by cold fronts inside the cool core, but with a faint extension beyond the core. Similarly to A3444, we find a cold front at r ~ 425 kpc, containing the radio emission. Thus the entire diffuse radio emission seen in these clusters appears to be related to large-scale sloshing of the ICM. The radio spectrum of the A3444 minihalo is a power law with a steep index α = 1.0 ± 0.1. The spectrum steepens with increasing distance from the center, as expected if the minihalo originates from reacceleration of relativistic particles by the sloshing-induced turbulence in the ICM.

Keywords: galaxy clusters; extragalactic astronomy; radio astronomy; intracluster medium
Mesoscale Phenomena during a Macroscopic Solar Eruption

Our previous magnetohydrodynamic simulation of a macroscopic solar eruption discussed in Zhao et al. (2019) showed that the current sheet (CS) evolution during eruption went through four stages: the CS growth stage, the dynamic growth stage, the hot CS stage, and the dynamic hot CS stage. We now focus on various mesoscale phenomena associated with the ongoing reconnection. In the dynamic growth stage, the remnant chromospheric matter in the CS is quasi-periodically pushed into the prominence, inducing fast shocks propagating at a speed of 210 km s-1. In the hot CS phase, various shock features relevant for particle acceleration are identified throughout the flare loop. Finally, during both dynamic stages, we quantify the properties of magnetic islands. A typical island is accelerated to Alfvénic speed by the Lorentz force and cools down by radiative cooling and thermal conduction. It also tends to expand in size before colliding with another island, with the FR or with the flare arcade. Islands in the dynamic growth stage have a higher density and lower temperature, and vice versa in the dynamic hot CS stage. Islands tend to move upward in the dynamic growth stage, while almost equal fractions of downward-moving and upward-moving islands in the dynamic hot CS stage. Translating the island trajectories to phase space, we find that the function $\dot{y}=({{ay}}^{2}+{by}+c)\exp (\lambda y)$ fits the trajectory well, and its two fixed points represent the creation and the annihilation of the island.

Keywords: magnetohydrodynamical simulations; solar magnetic reconnection; solar flares; termination shock; solar prominences
Observing Scenarios for the Next Decade of Early Warning Detection of Binary Neutron Stars

We describe representative observing scenarios for early warning detection of binary neutron star mergers with the current generation of ground-based gravitational wave detectors as they approach design sensitivity. We incorporate recent estimates of the infrastructure latency and detector sensitivities to provide up-to-date predictions. We use Fisher analysis to approximate the associated localizations, and we directly compare to Bayestar to quantify biases inherited from this approach. In particular, we show that Advanced LIGO and Advanced Virgo will detect and distribute ≲1 signal with signal-to-noise ratio greater than 15 before a merger in their fourth observing run provided they maintain a 70% duty cycle. This is consistent with previous early warning detection estimates. We estimate that 60% of all observations and 8% of those detectable 20 s before a merger will be localized to ≲100 deg2. If KAGRA is able to achieve a 25 Mpc horizon, 70% of these binary neutron stars will be localized to ≲100 deg2 by a merger. As the Aundha-Hanford-KAGRA-Livingston-Virgo network approaches design sensitivity over the next ~10 yr, we expect one (six) early warning alerts to be distributed 60 (0) s before a merger. Although adding detectors to the Hanford-Livingston-Virgo network at design sensitivity impacts the detection rate at ≲50% level, it significantly improves localization prospects. Given uncertainties in sensitivities, participating detectors, and duty cycles, we consider 103 future detector configurations so electromagnetic observers can tailor preparations toward their preferred models.

Keywords: neutron stars; compact objects; gravitational wave astronomy; gravitational waves; time domain astronomy; transient sources
Predicting the Kinematic Evidence of Gravitational Instability

Observations with the Atacama Large Millimeter/Submillimeter Array (ALMA) have dramatically improved our understanding of the site of exoplanet formation: protoplanetary disks. However, many basic properties of these disks are not well understood. The most fundamental of these is the total disk mass, which sets the mass budget for planet formation. Disks with sufficiently high masses can excite gravitational instability and drive spiral arms that are detectable with ALMA. Although spirals have been detected in ALMA observations of the dust, their association with gravitational instability, and high disk masses, is far from clear. Here we report a prediction for kinematic evidence of gravitational instability. Using hydrodynamics simulations coupled with radiative transfer calculations, we show that a disk undergoing such instability has clear kinematic signatures in molecular line observations across the entire disk azimuth and radius, which are independent of viewing angle. If these signatures are detected, it will provide the clearest evidence for the occurrence of gravitational instability in planet-forming disks, and provide a crucial way to measure disk masses.

Keywords: protoplanetary disks
The SNAD Viewer: Everything You Want to Know about Your Favorite ZTF Object

We describe the SNAD Viewer, a web portal for astronomers which presents a centralized view of individual objects from the Zwicky Transient Facility's (ZTF) data releases, including data gathered from multiple publicly available astronomical archives and data sources. Initially built to enable efficient expert feedback in the context of adaptive machine learning applications, it has evolved into a full-fledged community asset that centralizes public information and provides a multi-dimensional view of ZTF sources. For users, we provide detailed descriptions of the data sources and choices underlying the information displayed in the portal. For developers, we describe our architectural choices and their consequences such that our experience can help others engaged in similar endeavors or in adapting our publicly released code to their requirements. The infrastructure we describe here is scalable and flexible and can be personalized and used by other surveys and for other science goals. The Viewer has been instrumental in highlighting the crucial roles domain experts retain in the era of big data in astronomy. Given the arrival of the upcoming generation of large-scale surveys, we believe similar systems will be paramount in enabling an optimal exploitation of the scientific potential enclosed in current terabyte and future petabyte-scale data sets. The Viewer is publicly available online at https://ztf.snad.space.

Keywords: variable stars; astronomy software; open source software; publicly available software; astronomy web services
Seeing the Unseen: A Method to Detect Unresolved Rings in Protoplanetary Disks

While high-resolution Atacama Large Millimeter/submillimeter Array (ALMA) observations reveal a wealth of substructure in protoplanetary disks, they remain incapable of resolving the types of small-scale dust structures predicted, for example, by numerical simulations of the streaming instability. In this article, we propose a method to find evidence for unresolved, optically thick dusty rings in protoplanetary disks. We demonstrate that, in presence of unresolved rings, the brightness of an inclined disk exhibits a distinctive emission peak at the minor axis. Furthermore, the azimuthal brightness depends on both the geometry of the rings and the dust optical properties; we can therefore use the azimuthal brightness variations to both detect unresolved rings and probe their properties. By analyzing the azimuthal brightness in the test case of ringlike substructures formed by streaming instability, we show that the resulting peak is likely detectable by ALMA for typical disk parameters. Moreover, we present an analytic model that not only qualitatively but also quantitatively reproduces the peak found in the simulations, validating its applicability to infer the presence of unresolved rings in observations and characterize their optical properties and shape. This will contribute to the identification of disk regions where streaming instability (and thus planet formation) is occurring.

Keywords: protoplanetary disks; circumstellar disks; planetary system formation; planet formation; stellar accretion disks; dust continuum emission; hydrodynamical simulations