Sazuna/UAT_keywords huggingface dataset:
Homologous Flaring Activity over a Sunspot Light Bridge in an Emerging Active Region. Sunspot light bridges are known to exhibit a variety of dynamic and persistent phenomena such as surges, small-scale jets, etc., in the chromosphere and transition region. While it has generally been proposed that magnetic reconnection is responsible for this small-scale dynamism, persistent flaring activity lasting several hours from the same spatial location on a sunspot light bridge has rarely been reported. We combine observations from the Atmospheric Imaging Assembly and the Helioseismic Magnetic Imager on board the Solar Dynamics Observatory to investigate homologous flaring activity over a small sunspot light bridge in an emerging flux region. The homologous flares all produced broad, collimated jets including a B6.4 class flare. The jets rise at a speed of about 200 km s-1, reach projected heights of about 98 Mm, and emerge from the same spatial location for nearly 14 hrs, after which they cease completely. A nonlinear force-free extrapolation of the photospheric magnetic field shows a low-lying flux rope connecting the light bridge to a remote opposite-polarity network. The persistent flares occur as a result of the rapid horizontal motion of the leading sunspot that causes the relatively vertical magnetic fields in the adjacent umbra to reconnect with the low-lying flux rope in the light bridge. Our results indicate that the flaring ceases once the flux rope has lost sufficient twist through repeated reconnections.

Keywords: Solar flares, Solar magnetic flux emergence, Solar magnetic reconnection, Sunspots, Solar corona, Solar chromosphere
Kepler-411 Differential Rotation from Three Transiting Planets. The differential rotation of the Sun is a crucial ingredient of the dynamo theory responsible for the generation of its magnetic field. Currently, the rotation profile of a star that hosts one or more transiting planet can be estimated. By detecting the same spot in a later transit, it is possible to infer the stellar rotation period at that latitude. In this work, we apply for the first time transit spot mapping to determine the differential rotation of Kepler-411, a K2V-type star with an average rotation period of 10.52 days, a radius of 0.79 R⊙, and a mass of 0.83 M⊙. Kepler-411 hosts at least four planets, the inner planet is a super-Earth with a radius of 1.88 R⊕ and an orbital period of 3.0051 days, whereas the two larger transiting planets are mini Neptunes with radii of 3.27 and 3.31 R⊕, and periods of 7.834435 and 58.0204 days, respectively. Their orbits are such that they transit the star at latitudes of -11°, -21°, and -49°. Analysis of the transit light curves of the three planets resulted in the detection of a total of 198 spots. For each transit latitude, the rotation period of the star was estimated and the differential rotation pattern estimated independently. Then a solar-like differential rotation profile was fit to the three rotation periods at the distinct latitudes, and the result agreed extremely well with the previous ones, resulting in a differential shear of 0.0500 ± 0.0006 rd day-1 or a relative differential rotation of 8.4% ± 0.1%.

Keywords: Stellar photometry, Starspots, Transits, Exoplanet systems, Exoplanet astronomy, Stellar astronomy, Stellar physics, Transit photometry, Stellar rotation
ALMA Observation of SO<SUB>2</SUB> Gas Originating from Io's Volcanic Plume and Lava Areas. We detected the submillimeter spectrum of SO2 gas originating from volcanic plumes and lava areas in Jupiter's moon Io by analyzing the ALMA archive data observed before and after ingress on 2018 March. As a result of synthesis imaging, high intensity regions of SO2 were found to be associated with the volcanically active areas around the Amaterasu Patera (305°W, 38°N) and around the Janus Patera (36°W, 4°S) and Kanehekili Fluctus (32°W, 17°S). By fitting the spectral lineshapes, the main and redshifted spectral components are identified around the Amaterasu Patera. The redshifted component can be attributed as the emission from the plume gas moving away in the line of sight. The rotational temperature and column density of SO2 were derived by employing the population diagram plots with spectral line intensities. The column densities of SO2 before ingress are (2.2 ± 1.1) × 1015 cm-2 around the Amaterasu Patera and (2.2 ± 1.1) × 1015 cm-2 around the Janus Patera. After ingress, the column densities are (1.8 ± 1.2) × 1015 cm-2 and (2.1 ± 0.1) × 1015 cm-2, respectively. This suggests that volcanic eruptions maintain the atmospheres in these regions during eclipse. The temperature around the Amaterasu Patera of 95 ± 28 K before ingress is similar to the temperature of 108 ± 48 K after ingress. On the other hand, the temperature around the Janus Patera increases from 151 ± 70 K before ingress to 311 ± 41 K after ingress. The result suggests that the atmospheric SO2 around the Janus Patera after ingress may be supplied by evaporation from the lava areas.

Keywords: Planetary atmospheres
First Multi-redshift Limits on Post-Epoch of Reionization 21 cm Signal from z = 1.96-3.58 Using uGMRT. Measurement of fluctuations in diffuse HI 21 cm background radiation from the post-reionization epoch (z ≤ 6) is a promising avenue to probe the large-scale structure of the universe and understand the evolution of galaxies. We observe the European Large Area ISO Survey-North 1 (ELAIS-N1) field at 300-500 MHz using the upgraded Giant Meterwave Radio Telescope (uGMRT) and employ the "foreground avoidance" technique to estimate the HI 21 cm power spectrum in the redshift range z = 1.96-3.58. Given the possible systematics that may remain in the data, we find the most stringent upper limits on the spherically averaged 21 cm power spectra at k ∼ 1.0 Mpc-1 are (58.87 mK)2, (61.49 mK)2, (60.89 mK)2, and (105.85 mK)2 at z = 1.96, 2.19, 2.62, and 3.58, respectively. We use this to constrain the product of neutral HI mass density (ΩHI) and HI bias (bHI) to the underlying dark matter density field, [ΩHIbHI], as 0.09, 0.11, 0.12, and 0.24 at z = 1.96, 2.19, 2.62, and 3.58, respectively. To the best of our knowledge these are the first limits on the HI 21 cm power spectra at the redshift range z = 1.96-3.58 and would play a significant role to constrain the models of galaxy formation and evolution.

Keywords: Galaxy evolution, Large-scale structure of the universe
Recent Star Formation in a Massive Slowly Quenched Lensed Quiescent Galaxy at z = 1.88. In this Letter, we reconstruct the formation pathway of MRG-S0851, a massive, $\mathrm{log}{M}_{* }/{M}_{\odot }=11.02\pm 0.04$ , strongly lensed, red galaxy at z = 1.883 ± 0.001. While the global photometry and spatially resolved outskirts of MRG-S0851 imply an early formation scenario with a slowly decreasing or constant star formation history, a joint fit of 2D grism spectroscopy and photometry reveals a more complex scenario: MRG-S0851 is likely to be experiencing a centrally concentrated rejuvenation in the inner ∼1 kpc in the last ∼100 Myr of evolution. We estimate 0.5 ± 0.1% of the total stellar mass is formed in this phase. Rejuvenation episodes are suggested to be infrequent for massive galaxies at z ∼ 2, but as our analyses indicate, more examples of complex star formation histories may yet be hidden within existing data. By adding an FUV color criterion to the standard U-V/V-J diagnostic—thereby heightening our sensitivity to recent star formation—we show that we can select populations of galaxies with similar spectral energy distributions to that of MRG-S0851, but note that deep follow-up spectroscopic observations and/or spatially resolved analyses are necessary to robustly confirm the rejuvenation of these candidates. Using our criteria with MRG-S0851 as a prototype, we estimate that ∼1% of massive quiescent galaxies at 1 &lt; z &lt; 2 are potentially rejuvenating.

Keywords: Galaxy quenching, Galaxy formation, High-redshift galaxies, Galaxy stellar content
GW190521 May Be an Intermediate-mass Ratio Inspiral. GW190521 is the first confident observation of a binary black hole merger with total mass $M\gt 100\,{M}_{\odot }$ . Given the lack of observational constraints at these masses, we analyze GW190521 considering two different priors for the binary's masses: uniform in mass ratio and source-frame total mass, and uniform in source-frame component masses. For the uniform in mass-ratio prior, we find that the component masses are ${m}_{1}^{\mathrm{src}}={168}_{-61}^{+15}\,{M}_{\odot }$ and ${m}_{2}^{\mathrm{src}}={16}_{-3}^{+33}\,{M}_{\odot }$ . The uniform in component-mass prior yields a bimodal posterior distribution. There is a low-mass-ratio mode ( $q\lt 4$ ) with ${m}_{1}^{\mathrm{src}}={100}_{-18}^{+17}\,{M}_{\odot }$ and ${m}_{2}^{\mathrm{src}}={57}_{-16}^{+17}\,{M}_{\odot }$ and a high-mass-ratio mode ( $q\geqslant 4$ ) with ${m}_{1}^{\mathrm{src}}={166}_{-35}^{+16}\,{M}_{\odot }$ and ${m}_{2}^{\mathrm{src}}={16}_{-3}^{+14}\,{M}_{\odot }$ . Although the two modes have nearly equal posterior probability, the maximum-likelihood parameters are in the high-mass-ratio mode, with ${m}_{1}^{\mathrm{src}}=171\,{M}_{\odot }$ and ${m}_{2}^{\mathrm{src}}=16\,{M}_{\odot }$ , and a signal-to-noise ratio of 16. These results are consistent with the proposed "mass gap" produced by pair-instability in supernovae. Our results differ from those published in Abbott et al. We find that a combination of the prior used and the constraints applied may have prevented that analysis from sampling the high-mass-ratio mode. An accretion flare in AGN J124942.3+344929 was observed in possible coincidence with GW190521 by the Zwicky Transient Facility. We report parameters assuming a common origin; however, the spatial agreement of GW190521 and the electromagnetic flare alone does not provide convincing evidence for the association ( $\mathrm{ln}{ \mathcal B }\gtrsim -4$ ).

Keywords: Gravitational waves
Kinematic Analysis of a Protostellar Multiple System: Measuring the Protostar Masses and Assessing Gravitational Instability in the Disks of L1448 IRS3B and L1448 IRS3A. We present new Atacama Large Millimeter/submillimeter Array observations toward a compact (∼230 au separation) triple protostar system, L1448 IRS3B, at 879 μm with 0"11 × 0"05 resolution. Spiral arm structure within the circum-multiple disk is well resolved in dust continuum toward IRS3B, and we detect the known wide (∼2300 au) companion, IRS3A, also resolving possible spiral substructure. Using dense gas tracers, C17O (J = 3 $\to $ 2), H13CO+ (J = 4 $\to $ 3), and H13CN (J = 4 $\to $ 3), we resolve the Keplerian rotation for both the circum-triple disk in IRS3B and the disk around IRS3A. Furthermore, we use the molecular line kinematic data and radiative transfer modeling of the molecular line emission to confirm that the disks are in Keplerian rotation with fitted masses of ${1.19}_{-0.07}^{+0.13}$ M☉ for IRS3B-ab and ${1.51}_{-0.07}^{+0.06}$ M☉ for IRS3A and place an upper limit on the central protostar mass for the tertiary IRS3B-c of 0.2 M☉. We measure the mass of the fragmenting disk of IRS3B to be ∼0.29 M☉ from the dust continuum emission of the circum-multiple disk and estimate the mass of the clump surrounding IRS3B-c to be 0.07 M☉. We also find that the disk around IRS3A has a mass of ∼0.04 M☉. By analyzing the Toomre Q parameter, we find the IRS3A circumstellar disk is gravitationally stable (Q &gt; 5), while the IRS3B disk is consistent with a gravitationally unstable disk (Q &lt; 1) between the radii ∼200-500 au. This coincides with the location of the spiral arms and the tertiary companion IRS3B-c, supporting the hypothesis that IRS3B-c was formed in situ via fragmentation of a gravitationally unstable disk.

Keywords: Protostars, Young stellar objects
Probing the Cosmic-Ray Density in the Inner Galaxy. The galactic diffuse γ-ray emission, as seen by Fermi Large Area Telescope (LAT), shows a sharp peak in the region around 4 kpc from the Galactic center, which can be interpreted either as due to an enhanced density of cosmic-ray accelerators or to a modification of the particle diffusion in that region. Observations of γ-rays originating in molecular clouds are a unique tool to infer the cosmic-ray density point by point, in distant regions of the Galaxy. We report here the analysis of 11 yr Fermi-LAT data, obtained in the direction of nine molecular clouds located in the 1.5-4.5 kpc region. The cosmic-ray density measured at the locations of these clouds is compatible with the locally measured one. We demonstrate that the cosmic-ray density gradient inferred from the diffuse gamma-ray emission is the result of the presence of cosmic-ray accelerators rather than a global change of the sea of Galactic cosmic rays due to their propagation.

Keywords: Giant molecular clouds, Gamma-rays, Interstellar medium, Cosmic rays
The Clusters Hiding in Plain Sight (CHiPS) Survey: CHIPS1911+4455, a Rapidly Cooling Core in a Merging Cluster. We present high-resolution optical images from the Hubble Space Telescope, X-ray images from the Chandra X-ray Observatory, and optical spectra from the Nordic Optical Telescope for a newly discovered galaxy cluster, CHIPS1911+4455, at z = 0.485 ± 0.005. CHIPS1911+4455 was discovered in the Clusters Hiding in Plain Sight survey, which sought to discover galaxy clusters with extreme central galaxies that were misidentified as isolated X-ray point sources in the ROSAT All-Sky Survey. With new Chandra X-ray observations, we find the core (r = 10 kpc) entropy to be ${17}_{-9}^{+2}\,\mathrm{keV}\,{\mathrm{cm}}^{2}$ , suggesting a strong cool core, which is typically found at the centers of relaxed clusters. However, the large-scale morphology of CHIPS1911+4455 is highly asymmetric, pointing to a more dynamically active and turbulent cluster. Furthermore, the Hubble images reveal a massive, filamentary starburst near the brightest cluster galaxy (BCG). We measure the star formation rate for the BCG to be 140-190 M⊙ yr-1, which is one of the highest rates measured in a central cluster galaxy to date. One possible scenario for CHIPS1911+4455 is that the cool core was displaced during a major merger and rapidly cooled, with cool, star-forming gas raining back toward the core. This unique system is an excellent case study for high-redshift clusters, where such phenomena are proving to be more common. Further studies of such systems will drastically improve our understanding of the relation between cluster mergers and cooling, and how these fit in the bigger picture of active galactic nuclei feedback.

Keywords: Galaxy clusters, Starburst galaxies
A First-principle Simulation of Blast-wave Emergence at the Photosphere of a Neutron Star Merger. We present the first ab initio simulation of a radiation-mediated shock emerging at the photosphere of a relativistic outflow. The simulation is performed using our code radshock that follows fluid dynamics coupled to time-dependent radiative transfer, calculated with the Monte-Carlo method. We use the code to examine the radiative blast wave emerging from neutron star merger GW170817. It was previously proposed that the merger ejected a dark, relativistically expanding, homologous envelope, and then an explosion inside the envelope produced the observed gamma-ray burst GRB 170817A. Our simulation demonstrates how the shock wave generates radiation as it propagates through the envelope, approaches its photosphere, releases the radiation, and collapses, splitting into two collisionless shocks of a microscopic thickness. We find the light curve and the spectral evolution of the produced gamma-ray burst; both are similar to the observed GRB 170817A.

Keywords: Shocks, Gamma-ray bursts, Radiative transfer
Sustained Kozai-Lidov Oscillations in Misaligned Circumstellar Gas Disks. A disk around one component of a binary star system with sufficiently high inclination can undergo Kozai-Lidov (KL) oscillations during which the disk inclination and disk eccentricity are exchanged. Previous studies show that without a source of accretion, KL unstable disks exhibit damped oscillations, due to viscous dissipation, that leave the disk stable near or below the critical inclination for KL oscillations. With three-dimensional hydrodynamical simulations we show that a highly misaligned circumbinary disk that flows onto the binary components forms highly inclined circumstellar disks around each component. We show that a continuous infall of highly inclined material allows the KL oscillations to continue. The KL disk oscillations produce shocks and eccentricity growth in the circumstellar disks that affect the conditions for planet formation.

Keywords: Stellar accretion disks, Exoplanet formation, Binary stars
ALMA Survey of Orion Planck Galactic Cold Clumps (ALMASOP): Detection of Extremely High-density Compact Structure of Prestellar Cores and Multiple Substructures Within. Prestellar cores are self-gravitating dense and cold structures within molecular clouds where future stars are born. They are expected, at the stage of transitioning to the protostellar phase, to harbor centrally concentrated dense (sub)structures that will seed the formation of a new star or the binary/multiple stellar systems. Characterizing this critical stage of evolution is key to our understanding of star formation. In this work, we report the detection of high-density (sub)structures on the thousand-astronomical-unit (au) scale in a sample of dense prestellar cores. Through our recent ALMA observations toward the Orion Planck Galactic Cold Clumps, we have found five extremely dense prestellar cores, which have centrally concentrated regions of ∼2000 au in size, and several 107 cm-3 in average density. Masses of these centrally dense regions are in the range of 0.30 to 6.89 M⊙. For the first time, our higher resolution observations (0.8″ ∼ 320 au) further reveal that one of the cores shows clear signatures of fragmentation; such individual substructures/fragments have sizes of 800-1700 au, masses of 0.08 to 0.84 M⊙, densities of 2 - 8 × 107 cm-3, and separations of ∼1200 au. The substructures are massive enough (≳0.1 M⊙) to form young stellar objects and are likely examples of the earliest stage of stellar embryos that can lead to widely (∼1200 au) separated multiple systems.

Keywords: Star forming regions, Molecular clouds, Star formation, Protostars, Collapsing clouds
Icarus: A Flat and Fast Prograde Stellar Stream in the Milky Way Disk. We explore the local volume of the Milky Way via chemical and kinematical measurements from high-quality astrometric and spectroscopic data recently released by the Gaia, APOGEE, and GALAH programs. We chemically select 1137 stars up to 2.5 kpc of the Sun and [Fe/H] ≤ -1.0 dex, and find evidence of statistically significant substructures. Clustering analysis in velocity space classifies 163 objects into eight kinematical groups, whose origin is further investigated with high-resolution N-body numerical simulations of single merging events. The two retrograde groups appear associated with Gaia-Sausage-Enceladus (GSE), while the slightly prograde group could be connected to GSE or possibly Wukong. We find evidence of a new 44-member-strong prograde stream that we name Icarus; to our knowledge, Icarus is the fast-rotating stream closest to the Galactic disk to date ( $\langle {Z}_{\max }\rangle \lesssim 0.5\,\mathrm{kpc}$ , ⟨V + VLSR⟩ ≃ 231 km s-1). Its peculiar chemical (⟨[Fe/H]⟩ ≃ -1.45, ⟨[Mg/Fe]⟩ ≃ -0.02) and dynamical (mean eccentricity ≃ 0.11) properties are consistent with the accretion of debris from a dwarf galaxy progenitor with a stellar mass of ∼109M⊙ on an initial prograde low-inclination orbit, ∼10°. The remaining prograde groups are either streams previously released by the same progenitor of Icarus (or Nyx), or remnants from different satellites accreted on initial orbits at higher inclination.

Keywords: Stellar abundances, Milky Way stellar halo, Milky Way dynamics, Milky Way formation
The Peculiar Ca-rich SN2019ehk: Evidence for a Type IIb Core-collapse Supernova from a Low-mass Stripped Progenitor. The nature of the peculiar "Ca-rich" SN 2019ehk in the nearby galaxy M100 remains unclear. Its origin has been debated as either a stripped core-collapse supernova or a thermonuclear helium detonation event. Here, we present very late-time photometry of the transient obtained with the Keck I telescope at ≈280 days from peak light. Using the photometry to perform accurate flux calibration of a contemporaneous nebular phase spectrum, we measure an [O I] luminosity of (0.19-1.08) × 1038 erg s-1 and [Ca II] luminosity of (2.7-15.6) × 1038 erg s-1 over the range of the uncertain extinction along the line of sight and distance to the host galaxy. We use these measurements to derive lower limits on the synthesized oxygen mass of ≈0.004-0.069 M⊙. The oxygen mass is a sensitive tracer of the progenitor mass for core-collapse supernovae, and our estimate is consistent with explosions of very low-mass CO cores of 1.45-1.5 M⊙, corresponding to He core masses of ≈1.8-2.0 M⊙. We present high-quality peak light optical spectra of the transient and highlight features of hydrogen in both the early ("flash") and photospheric phase spectra that suggest the presence of ≳0.02 M⊙ of hydrogen in the progenitor at the time of explosion. The presence of H, together with the large [Ca II]/[O I] ratio (≈10-15) in the nebular phase, is consistent with SN 2019ehk being a Type IIb core-collapse supernova from a stripped low-mass (≈9-9.5 M⊙) progenitor, similar to the Ca-rich SN IIb iPTF 15eqv. These results provide evidence for a likely class of "Ca-rich" core-collapse supernovae from stripped low-mass progenitors in star-forming environments, distinct from the thermonuclear Ca-rich gap transients in old environments.

Keywords: Massive stars, Nucleosynthesis, Oxygen burning, Core-collapse supernovae
Massive Stellar Triples Leading to Sequential Binary Black Hole Mergers in the Field. Stellar triples with massive stellar components are common and can lead to sequential binary black hole mergers. Here we outline the evolution toward these sequential mergers and explore these events in the context of gravitational-wave astronomy and the pair-instability mass gap. We find that binary black hole mergers in the pair-instability mass gap can be of triple origin and therefore are not exclusively formed in dense dynamical environments. We discuss the sequential merger scenario in the context of the most massive gravitational-wave sources detected to date: GW170729 and GW190521. We propose that the progenitor of GW170729 is a low-metallicity field triple. We support the premise that GW190521 could not have been formed in the field. We conclude that triple stellar evolution is fundamental to the understanding of gravitational-wave sources and likely other energetic transients as well.

Keywords: Astrophysical black holes