Sazuna/UAT_keywords huggingface dataset:
Excitation Sources of Oscillations in Solar Coronal Loops: A Multi-wavelength Analysis. An investigation into the excitation sources of oscillations detected in a coronal loop structure is carried out using the images obtained with Interface Region Imaging Spectrometer (IRIS) and the Atmospheric Imaging Assembly (AIA) instrument on board the Solar Dynamics Observatory (SDO). A loop structure in the active region AR 11967 on 2014 January 28, oscillating in the vicinity of a strong eruption and an M3.6 class flare site, is clearly noticeable in SDO/AIA 171 Å images. We study in detail, the oscillations with detected periods between 4 and 13 minutes and their connection in IRIS SJI 1330 Å and SDO/AIA 1700 Å images; both of these wavelengths sample the lower parts of the solar atmosphere. The simultaneous presence of many oscillations in the region of interest in all three wavelength passbands suggest that these oscillations were excited in the lower-chromosphere-photosphere plasma connected to the loop structure and then propagated at higher heights. We further investigate the Doppler velocity measurements from the spectrograph snapshots in IRIS C II 1336 Å, Si IV 1403 Å and Mg II k 2796 Å. These show signatures of upflows in the vicinity of the loop structure's endpoints estimated from 171 Å images. We suggest that some of the oscillations observed in AIA 171 Å have been triggered by plasma ejections and perturbations seen in the lower layers of the solar atmosphere. Based on the estimated phase speeds, the oscillations are likely to be slow magnetoacoustic in nature.

Keywords: Solar atmosphere, Solar physics, Solar corona
<SUP>13</SUP>CH<SUB>3</SUB>OH Masers Associated With a Transient Phenomenon in a High-mass Young Stellar Object. We report the first detection of isotopic methanol (13CH3OH) maser emission in interstellar space. The emission was detected toward the high-mass young stellar object G358.93-0.03 during monitoring of a flare in the 6.7 GHz methanol (CH3OH) maser emission in this source. We find that the spectral and spatial distribution of the 13CH3OH masers differs from the CH3OH masers imaged at the same epoch, contrary to expectations from similarity of their pumping. This conclusively demonstrates that isotopic methanol masers are bright under different physical conditions and suggests that they can provide additional, complementary information to the CH3OH masers from the same source. We detect a rapid decay of the 13CH3OH maser lines suggesting that they are transient phenomena (masing for only a few months), likely associated with rapid changes in radiation field due to an accretion burst induced by massive disk fragmentation. Changes in the line flux density are faster than required to achieve equilibrium in the energy level populations, indicating that the pumping of these masers is likely variable.

Keywords: Interstellar molecules, Star formation, Astrophysical masers, Interstellar masers, Stellar accretion disks
Space Weathering Simulation with Low-energy Laser Irradiation of Murchison CM Chondrite for Reproducing Micrometeoroid Bombardments on C-type Asteroids. Micrometeoroid bombardments are one of the causes of space weathering on airless bodies. We have simulated micrometeoroid bombardments on the surfaces of C-type asteroids by pulse-laser irradiation experiments on Murchison CM2 chondrite samples. In this Letter, we focus in particular on the effect of lower-energy irradiation compared to our previous study, where the laser energy range was set to 5-15 mJ, causing spectral flattening and water absorption band suppression. Murchison powder samples were irradiated with pulse lasers of various laser intensities (0.7, 1, 2, and 5 mJ). The irradiation energies are equivalent to micrometeoroid bombardments on the main-belt asteroids for ∼5.7 × 107 yr for 5 mJ and ∼7.9 × 106 yr for 0.7 mJ, respectively. We measured reflectance spectra and analyzed chemical compositions and microstructures of the surface of the laser-irradiated Murchison samples. Laser-irradiated Murchison spectra show flattening and darkening in the ultraviolet (UV)-visible (Vis)-infrared (IR) range. As the laser energy was increased up to 5 mJ, the 3 and 0.7 μm band depths decreased by 12% and 50%, respectively. The particle surface in the 5 mJ irradiated area shows melted and vesiculated structures, indicating high-temperature heating by laser irradiation followed by rapid cooling. The chemical composition of the melted and bubbled portions is similar to FeS-rich amorphous silicate particles observed in the high-energy laser irradiation case. Each mineralogical change of Murchison due to short-duration heating would cause spectral bluing, darkening, and absorption band suppression.

Keywords: Carbonaceous chondrites, Laboratory astrophysics, Spectroscopy
Fast Radio Bursts from Interacting Binary Neutron Star Systems. Recent observations of repeating fast radio bursts (FRBs) suggest that some FRBs reside in an environment consistent with that of binary neutron star (BNS) mergers. The bursting rate for repeaters could be very high and the emission site is likely from a magnetosphere. We discuss a hypothesis of producing abundant repeating FRBs in BNS systems. Decades to centuries before a BNS system coalesces, the magnetospheres of the two neutron stars start to interact relentlessly. Abrupt magnetic reconnection accelerates particles, which emit coherent radio waves in bunches via curvature radiation. FRBs are detected as these bright radiation beams point toward Earth. This model predicts quasi-periodicity of the bursts at the rotation periods of the two merging neutron stars (tens of milliseconds and seconds, respectively) as well as the period of orbital motion (of the order of 100 s). The bursting activities are expected to elevate with time as the two neutron stars get closer. The repeating FRB sources should be gravitational-wave (GW) sources for space-borne detectors such as Laser Interferometer Space Antenna (LISA), and eventually could be detected by ground-based detectors when the two neutron stars coalesce.

Keywords: Gravitational waves, Interacting binary stars, Radio transient sources
Stellar Kinematics and Environment at z ∼ 0.8 in the LEGA-C Survey: Massive Slow Rotators Are Built First in Overdense Environments. In this Letter, we investigate the impact of environment on integrated and spatially resolved stellar kinematics of a sample of massive, quiescent galaxies at intermediate redshift (0.6 &lt; z &lt; 1.0). For this analysis, we combine photometric and spectroscopic parameters from the UltraVISTA and Large Early Galaxy Astrophysics Census surveys in the COSMOS field and environmental measurements. We analyze the trends with overdensity (1+δ) on the rotational support of quiescent galaxies and find no universal trends at either fixed mass or fixed stellar velocity dispersion. This is consistent with previous studies of the local universe; rotational support of massive galaxies depends primarily on stellar mass. We highlight two populations of massive galaxies ( $\mathrm{log}\,{M}_{\star }/{M}_{\odot }\geqslant 11$ ) that deviate from the average mass relation. First, the most massive galaxies in the most underdense regions ((1 + δ) ≤ 1) exhibit elevated rotational support. Similarly, at the highest masses ( $\mathrm{log}\,{M}_{\star }/{M}_{\odot }\geqslant 11.25$ ) the range in rotational support is significant in all but the densest regions. This corresponds to an increasing slow-rotator fraction such that only galaxies in the densest environments ((1 + δ) ≥ 3.5) are primarily (90% ± 10%) slow rotators. This effect is not seen at fixed velocity dispersion, suggesting minor merging as the driving mechanism: only in the densest regions have the most massive galaxies experienced significant minor merging, building stellar mass and diminishing rotation without significantly affecting the central stellar velocity dispersion. In the local universe, most massive galaxies are slow rotators, regardless of environment, suggesting minor merging occurs at later cosmic times (z ≲ 0.6) in all but the most dense environments.

Keywords: Galaxy formation, Quenched galaxies, Galaxy evolution, Galaxies
Rapid Transients Originating from Thermonuclear Explosions in Helium White Dwarf Tidal Disruption Events. We study the emission properties of thermonuclear explosions in a helium white dwarf (WD) tidal disruption event (TDE). We consider a TDE where a 0.2 M⊙ helium WD is disrupted by a 102.5 M⊙ intermediate-mass black hole (IMBH). The helium WD is not only tidally disrupted but is also detonated by the tidal compression and by succeeding shocks. We focus on the emission powered by radioactive nuclei in the unbound TDE ejecta. We perform hydrodynamic simulations coupled with nuclear reactions, post-process detailed nucleosynthesis calculations, and radiative transfer simulations. We thus derive multi-band light curves and spectra. The helium WD TDE shows rapid (Δt1mag ≃ 5-10 days) and relatively faint ( ${L}_{\mathrm{peak}}\simeq {10}^{42}\,\mathrm{erg}\,{{\rm{s}}}^{-1}$ ) light curves, because the ejecta mass and 56Ni mass are low (0.12 M⊙ and 0.03 M⊙, respectively). The spectra show strong calcium and Fe-peak features and very weak silicon features, reflecting the peculiar elemental abundance. The key feature is the Doppler shift of the spectral lines up to ≃ ±12,000 km s-1, depending on the viewing angle, due to the bulk motion of the ejecta. Our model matches well with two rapid and faint transients reported in Pursiainen et al. The particular model presented here does not match with observed SNe Iax, calcium-rich transients, or .Ia explosion candidates, either in the spectra or light curves. However, we expect a large variety of observational signatures once a wide range of the WD/black hole masses and orbital parameters are considered. This study contributes to the search for WD TDEs with current and upcoming surveys, and to the identification of IMBHs as disrupters in TDEs.

Keywords: Intermediate-mass black holes, Hydrodynamical simulations, Explosive nucleosynthesis, Black holes, Nucleosynthesis, White dwarf stars, Tidal disruption, Helium burning, Radiative transfer, Radiative transfer simulations, Supernovae, Astronomical simulations
Evidence for Spin-Orbit Alignment in the TRAPPIST-1 System. In an effort to measure the Rossiter-McLaughlin effect for the TRAPPIST-1 system, we performed high-resolution spectroscopy during transits of planets e, f, and b. The spectra were obtained with the InfraRed Doppler spectrograph on the Subaru 8.2 m telescope, and were supplemented with simultaneous photometry obtained with a 1 m telescope of the Las Cumbres Observatory Global Telescope. By analyzing the anomalous radial velocities, we found the projected stellar obliquity to be λ = 1 ± 28° under the assumption that the three planets have coplanar orbits, although we caution that the radial-velocity data show correlated noise of unknown origin. We also sought evidence for the expected deformations of the stellar absorption lines, and thereby detected the "Doppler shadow" of planet b with a false-alarm probability of 1.7%. The joint analysis of the observed residual cross-correlation map including the three transits gave $\lambda ={19}_{-15}^{+13}$ °. These results indicate that the the TRAPPIST-1 star is not strongly misaligned with the common orbital plane of the planets, although further observations are encouraged to verify this conclusion.

Keywords: High resolution spectroscopy, Radial velocity, Transit photometry, Extrasolar rocky planets
Spatially Resolved UV Diagnostics of AGN Feedback: Radiation Pressure Dominates in a Prototypical Quasar-driven Superwind. Galactic-scale winds driven by active galactic nuclei (AGN) are often invoked to suppress star formation in galaxy evolution models, but the mechanisms driving these outflows are hotly debated. Two key AGN feedback models are (1) radiation pressure accelerating cool gas and (2) a hot outflowing wind entraining the interstellar medium (ISM). Highly ionized emission-line diagnostics represent a powerful means of differentiating these scenarios because of their sensitivity to the expected compression of the ISM clouds by the hot wind. Here, we report the first spatially resolved UV emission spectroscopy of a prototypical (radio-quiet) quasar-driven superwind around the obscured quasar SDSS J1356+1026 at z = 0.123. We observe ratios of O VI/C IV, N V/C IV, and C IV/He II that are remarkably similar for outflowing gas clouds ≲100 pc and ≈10 kpc from the nucleus. Such similarity is expected for clouds with AGN radiation-pressure-dominated dynamics. Comparing the observed line emission to models of clouds in balance with radiation pressure and/or a hot wind, we rule out the presence of a dynamically important hot wind and constrain the ratio of hot gas pressure to radiation pressure to Phot/Prad ≲ 0.25 both at ≲100 pc and ≈10 kpc from the nucleus. Moreover, the predictions of the radiation pressure confined cloud models that best fit observed UV line ratios are consistent with the observed diffuse X-ray spectrum. These results indicate that this AGN superwind is driven by radiation pressure or was driven by a hot wind that has since dissipated despite ongoing AGN activity.

Keywords: Galactic winds, Supermassive black holes, Quasars, Active galaxies, Active galactic nuclei
X-Ray Spectral Shape Variation in Changing-look Seyfert Galaxy SDSS J155258+273728. We analyze the X-ray, optical, and mid-infrared data of a "changing-look" Seyfert galaxy SDSS J155258+273728 at z ≃ 0.086. Over a period of one decade (2009-2018), its broad Hα line intensity increased by a factor of ∼4. Meanwhile, the X-ray emission in 2014 as observed by Chandra was about five times brighter than that in 2010 by Suzaku, and the corresponding emissions in the V-band, mid-infrared W1 band brighten by ∼0.18, 0.32 mag, respectively. Moreover, the absorption in X-rays is moderate and stable, I.e., ${N}_{{\rm{H}}}\sim {10}^{21}\ {\mathrm{cm}}^{-2}$ , but the X-ray spectrum becomes harder in the 2014 Chandra bright state (I.e., photon index ${\rm{\Gamma }}={1.52}_{-0.06}^{+0.06}$ ) than that of the 2010 Suzaku low state ( ${\rm{\Gamma }}={2.03}_{-0.21}^{+0.22}$ ). With an Eddington ratio being lower than a few percent, the inner region of the accretion disk in SDSS J155258+273728 is likely a hot accretion flow. We then compile from literature the X-ray data of "changing-look" active galactic nuclei (AGNs), and find that they generally follow the well-established "V"-shaped correlation in AGNs, that is, above a critical turnover luminosity the X-ray spectra soften with the increasing luminosity, and below that luminosity the trend is reversed in the way of "harder when brighter." This presents direct evidence that CL-AGNs have distinctive changes in not only the optical spectral type, but also the X-ray spectral shape. The similarity in the X-ray spectral evolution between CL-AGNs and black hole X-ray binaries indicates that the observed CL-AGNs phenomena may relate to the state transition in accretion physics.

Keywords: Active galactic nuclei, Galaxies, Quasars
Simple Yet Powerful: Hot Galactic Outflows Driven by Supernovae. Supernovae (SNe) drive multiphase galactic outflows, impacting galaxy formation; however, cosmological simulations mostly use ad hoc feedback models for outflows, making outflow-related predictions from first principles problematic. Recent small-box simulations resolve individual SNe remnants in the interstellar medium (ISM), naturally driving outflows and permitting a determination of the wind loading factors of energy ηE, mass ${\eta }_{m}$ , and metals ${\eta }_{Z}$ . In this Letter, we compile small-box results, and find consensus that the hot outflows are much more powerful than the cool outflows: (I) hot outflows generally dominate the energy flux, and (II) their specific energy es,h is 10-1000 times higher than cool outflows. Moreover, the properties of hot outflows are remarkably simple: ${e}_{s,h}\propto {\eta }_{E,h}/{\eta }_{m,h}$ is almost invariant over four orders of magnitude of star formation surface density. Also, we find tentatively that ${\eta }_{E,h}/{\eta }_{Z,h}\sim $ 0.5. If corroborated by more simulation data, these correlations reduce the three hot phase loading factors into one. Finally, this one parameter is closely related to whether the ISM has a "breakout" condition. The narrow range of ${e}_{s,h}$ indicates that hot outflows cannot escape dark matter halos with log ${M}_{\mathrm{halo}}\ [{M}_{\odot }]\gtrsim 12$ . This mass is also where the galaxy mass-metallicity relation reaches its plateau, implying a deep connection between hot outflows and galaxy formation. We argue that hot outflows should be included explicitly in cosmological simulations and (semi-)analytic modeling of galaxy formation.

Keywords: Galactic winds, Galaxy formation, Hydrodynamical simulations, Stellar feedback, Galaxy chemical evolution, Chemical enrichment, Galaxy evolution, Interstellar medium, Metallicity
Mutual Inclination Excitation by Stellar Oblateness. Ultra-short-period planets (USPs) provide important clues to planetary formation and migration. It was recently found that the mutual inclinations of the planetary systems are larger if the inner orbits are closer (≲5R*) and if the planetary period ratios are larger (P2/P1 ≳ 5). This suggests that the USPs experienced both inclination excitation and orbital shrinkage. Here we investigate the increase in the mutual inclination due to stellar oblateness. We find that the stellar oblateness (within ∼1 Gyr) is sufficient to enhance the mutual inclination to explain the observed signatures. This suggests that the USPs can migrate closer to the host star in a near coplanar configuration with their planetary companions (e.g., disk migration+tides or in situ+tides), before mutual inclination gets excited due to stellar oblateness.

Keywords: Exoplanet dynamics, Exoplanet systems
AGILE Observations of Two Repeating Fast Radio Bursts with Low Intrinsic Dispersion Measures. We focus on two repeating fast radio bursts (FRBs) recently detected by the CHIME/FRB experiment in 2018-2019 (Source 1: 180916.J0158+65, and Source 2: 181030.J1054+73). These sources have low excess dispersion measures ( $\lt 100\,\mathrm{pc}\,{\mathrm{cm}}^{-3}$ and $\lt 20\,\mathrm{pc}\,{\mathrm{cm}}^{-3}$ , respectively), implying relatively small maximal distances. They were repeatedly observed by AGILE in the MeV-GeV energy range. We do not detect prompt emission simultaneously with these repeating events. This search is particularly significant for the submillisecond and millisecond integrations obtainable by AGILE. The sources are constrained to emit a MeV-fluence in the millisecond range below $F{{\prime} }_{\mathrm{MeV}}={10}^{-8}\,\mathrm{erg}\,{\mathrm{cm}}^{-2}$ corresponding to an isotropic energy near ${E}_{\mathrm{MeV},\mathrm{UL}}\simeq 2\times {10}^{46}$ erg for a distance of 150 Mpc (applicable to Source 1). We also searched for γ-ray emission for time intervals up to 100 days, obtaining 3σ upper limits (ULs) for the average isotropic luminosity above 50 MeV, ${L}_{\gamma ,\mathrm{UL}}\,\simeq $ (5-10) $\,\times \,{10}^{43}\,\mathrm{erg}\,{{\rm{s}}}^{-1}$ . For a source distance near 100 kpc (possibly applicable to Source 2), our ULs imply ${E}_{\mathrm{MeV},\mathrm{UL}}\simeq {10}^{40}\,\mathrm{erg}$ , and ${L}_{\gamma ,\mathrm{UL}}\,\simeq $ 2 $\times {10}^{37}\,\mathrm{erg}\,{{\rm{s}}}^{-1}$ . Our results are significant in constraining the high-energy emission of underlying sources such as magnetars, or other phenomena related to extragalactic compact objects, and show the prompt emission to be lower than the peak of the 2004 magnetar outburst of SGR 1806-20 for source distances less than about 100 Mpc.

Keywords: Magnetars, X-ray transient sources, Gamma-ray transient sources, Radio transient sources
Discovery of a Giant Radio Fossil in the Ophiuchus Galaxy Cluster. The Ophiuchus galaxy cluster exhibits a curious concave gas density discontinuity at the edge of its cool core. It was discovered in the Chandra X-ray image by Werner and collaborators, who considered the possibility of it being a boundary of an active galactic nucleus (AGN)-inflated bubble located outside the core, but discounted this possibility because it required much too powerful an AGN outburst. Using low-frequency (72-240 MHz) radio data from the Murchison Widefield Array/GLEAM and the Giant Metrewave Radio Telescope, we found that the X-ray structure is, in fact, a giant cavity in the X-ray gas filled with diffuse radio emission with an extraordinarily steep radio spectrum. It thus appears to be a very aged fossil of the most powerful AGN outburst seen in any galaxy cluster (pV ∼ 5 × 1061 erg for this cavity). There is no apparent diametrically opposite counterpart either in X-ray or in the radio. It may have aged out of the observable radio band because of the cluster asymmetry. At present, the central AGN exhibits only a weak radio source, so it should have been much more powerful in the past to have produced such a bubble. The AGN is currently starved of accreting cool gas because the gas density peak is displaced by core sloshing. The sloshing itself could have been set off by this extraordinary explosion if it had occurred in an asymmetric gas core. This dinosaur may be an early example of a new class of sources to be uncovered by low-frequency surveys of galaxy clusters.

Keywords: Galaxy clusters, Cooling flows, Extragalactic radio sources, Active galaxies, Intracluster medium
The GRIFFIN Project—Formation of Star Clusters with Individual Massive Stars in a Simulated Dwarf Galaxy Starburst. We describe a population of young star clusters (SCs) formed in a hydrodynamical simulation of a gas-rich dwarf galaxy merger resolved with individual massive stars at subparsec spatial resolution. The simulation is part of the griffin (Galaxy Realizations Including Feedback From INdividual massive stars) project. The star formation environment during the simulation spans seven orders of magnitude in gas surface density and thermal pressure, and the global star formation rate surface density (ΣSFR) varies by more than three orders of magnitude during the simulation. Young SCs more massive than M_{*,cl}∼ 102.5 M_{⊙} form along a mass function with a power-law index α ∼ -1.7 (α ∼ -2 for M_{*,cl}≳ 103 M_{⊙}) at all merger phases, while the normalization and the highest SC masses (up to ∼106 M⊙) correlate with ΣSFR. The cluster formation efficiency varies from Γ ∼ 20% in early merger phases to Γ ∼ 80% at the peak of the starburst and is compared to observations and model predictions. The massive SCs (≳104 M⊙) have sizes and mean surface densities similar to observed young massive SCs. Simulated lower mass clusters appear slightly more concentrated than observed. All SCs form on timescales of a few Myr and lose their gas rapidly resulting in typical stellar age spreads between σ ∼ 0.1-2 Myr (1σ), consistent with observations. The age spreads increase with cluster mass, with the most massive cluster (∼106 M⊙) reaching a spread of 5 Myr once its hierarchical formation finishes. Our study shows that it is now feasible to investigate the SC population of entire galaxies with novel high-resolution numerical simulations.

Keywords: Galaxy interactions, Dwarf galaxies, Computational methods, Star formation, Star clusters