Sazuna/UAT_keywords huggingface dataset:
Near-infrared Spectroscopy of CK Vulpeculae: Revealing a Remarkably Powerful Blast from the Past. CK Vulpeculae (CK Vul), which erupted in AD 1670-71, was long considered to be a nova outburst; however, recent observations have required that alternative scenarios be considered. Long-slit infrared spectroscopy of a forbidden line of iron reported here has revealed high line-of-sight velocities (∼±900 km s-1) of the ansae at the tips of the bipolar lobes imaged in Hα in 2010. The deprojected velocities of the tips are approximately ±2130 km s-1 assuming the previously derived inclination angle of 65° for the axis of cylindrical symmetry of the bipolar nebula. Such high velocities are in stark contrast to previous reports of much lower expansion velocities in CK Vul. Based on the deprojected velocities of the tips and their angular expansion measured over a 10 yr baseline, we derive a revised estimate, with estimated uncertainties, of ${3.2}_{-0.6}^{+0.9}$ kpc for the distance to CK Vul. This implies that the absolute visual magnitude at the peak of the 1670 explosion was ${M}_{V}=-{12.4}_{-2.4}^{+1.3}$ , indicating that the 1670 event was far more luminous than previous estimates and brighter than any classical nova or any Galactic stellar merger. We propose that CK Vul belongs to the class of intermediate-luminosity optical transients (ILOTs), objects which bridge the luminosity gap between novae and supernovae. While eruptions in lower luminosity ILOTs are attributed to merger events, the origin of the highly luminous ILOT outbursts is currently not known.

Keywords: Stellar luminosities, Stellar phenomena, Stellar mass loss, Stellar winds, Infrared sources
ALMA CO Observations of the Gamma-Ray Supernova Remnant RX J1713.7-3946: Discovery of Shocked Molecular Cloudlets and Filaments at 0.01 pc Scales. RX J1713.7-3946 is a unique core-collapse supernova remnant (SNR) that emits bright TeV gamma-rays and synchrotron X-rays caused by cosmic rays, in addition to interactions with interstellar gas clouds. We report here on results of Atacama Large Millimeter/submillimeter Array 12CO(J = 1-0) observations toward the northwestern shell of the SNR. We newly found three molecular complexes consisting of dozens of shocked molecular cloudlets and filaments with typical radii of ∼0.03-0.05 pc and densities of ∼104 cm-3. These cloudlets and filaments are located not only along synchrotron X-ray filaments, but also in the vicinity of X-ray hotspots with month- or year-scale time variations. We argue that X-ray hotspots and filaments were generated by shock-cloudlet interactions through magnetic-field amplification up to mG. The interstellar medium density contrast of ∼105, coexistence of molecular cloudlets and low-density diffuse medium of ∼0.1 cm-3, is consistent with such a magnetic field amplification as well as a wind-bubble scenario. The small-scale cloud structures also affect hadronic gamma-ray spectra considering the magnetic field amplification on surface and inside clouds.

Keywords: Gamma-ray sources, Supernova remnants, Cosmic ray sources, X-ray sources, Interstellar medium
SCExAO/CHARIS Direct Imaging Discovery of a 20 au Separation, Low-mass Ratio Brown Dwarf Companion to an Accelerating Sun-like Star. We present the direct imaging discovery of a substellar companion to the nearby Sun-like star, HD 33632 Aa, at a projected separation of ∼20 au, obtained with SCExAO/CHARIS integral field spectroscopy complemented by Keck/NIRC2 thermal infrared imaging. The companion, HD 33632 Ab, induces a 10.5σ astrometric acceleration on the star as detected with the Gaia and Hipparcos satellites. SCExAO/CHARIS JHK (1.1-2.4 μm) spectra and Keck/NIRC2 Lp (3.78 μm) photometry are best matched by a field L/T transition object: an older, higher-gravity, and less dusty counterpart to HR 8799 cde. Combining our astrometry with Gaia/Hipparcos data and archival Lick Observatory radial velocities, we measure a dynamical mass of 46.4 ± 8 MJ and an eccentricity of e &lt; 0.46 at 95% confidence. HD 33632 Ab's mass and mass ratio (4.0% ± 0.7%) are comparable to the low-mass brown dwarf GJ 758 B and intermediate between the more massive brown dwarf HD 19467 B and the (near-)planet-mass companions to HR 2562 and GJ 504. Using Gaia to select for direct imaging observations with the newest extreme adaptive optics systems can reveal substellar or even planet-mass companions on solar system-like scales at an increased frequency compared to blind surveys. * Based in part on data collected at Subaru Telescope, which is operated by the National Astronomical Observatory of Japan.

Keywords: Brown dwarfs, Exoplanets, Astronomical optics, Coronagraphic imaging, Astronomical techniques, Direct imaging, Astronomical instrumentation, Exoplanet detection methods
Minding the Gap: GW190521 as a Straddling Binary. Models for black hole (BH) formation from stellar evolution robustly predict the existence of a pair-instability supernova (PISN) mass gap in the range ∼50 to ∼120 solar masses. This theoretical prediction is supported by the binary black holes (BBHs) of LIGO/Virgo's first two observing runs, whose component masses are well fit by a power law with a maximum mass cutoff at ${m}_{\max }={40.8}_{-4.4}^{+11.8}\,{\text{}}{M}_{\odot }$ . Meanwhile, the BBH event GW190521 has a reported primary mass of ${m}_{1}={85}_{-14}^{+21}\,{\text{}}{M}_{\odot }$ , firmly above the inferred ${m}_{\max }$ , and secondary mass ${m}_{2}={66}_{-18}^{+17}\ {\text{}}{M}_{\odot }$ . Rather than concluding that both components of GW190521 belong to a new population of mass-gap BHs, we explore the conservative scenario in which GW190521's secondary mass belongs to the previously observed population of BHs. We replace the default priors on m1 and m2, which assume that BH detector-frame masses are uniformly distributed, with this population-informed prior on m2, finding ${m}_{2}\lt 48\,{\text{}}{M}_{\odot }$ at 90% credibility. Moreover, because the total mass of the system is better constrained than the individual masses, the population prior on m2 automatically increases the inferred m1 to sit above the gap (39% for m1 &gt; 120 ${\text{}}{M}_{\odot }$ , or 25% probability for m1 &gt; 130 ${\text{}}{M}_{\odot }$ ). As long as the prior odds for a double-mass-gap BBH are smaller than $\sim 1\,:\,15$ , it is more likely that GW190521 straddles the pair-instability gap. We argue that GW190521 may be the first example of a straddling binary black hole, composed of a conventional stellar mass BH and a BH from the "far side" of the PISN mass gap.

Keywords: Intermediate-mass black holes, Bayesian statistics, Gravitational wave astronomy, Gravitational waves, Astrophysical black holes
The Role of Far-ultraviolet Pumping in Exciting the [O I] Lines in Protostellar Disks and Winds. We use Cloudy to re-examine excitation of [O I] 6300 Å and [O I] 5577 Å in the X-ray driven photoevaporative wind models of Owen and collaborators, and in more recent magnetothermal models by Wang et al. We find that, at the measured accretion luminosities, the far-ultraviolet (FUV) radiation would populate the upper levels of the oxygen, which would eventually contribute to the [O I] lines. FUV pumping competes with collisions as an excitation mechanism of the [O I] lines, and they each originate from a distinct region in the protostellar disk environment. Consequently, the line strengths and shapes of [O I] 6300 Å and [O I] 5577 Å would be affected by the inclusion of FUV pumping in the radiation transport simulations.

Keywords: Atomic spectroscopy, Protoplanetary disks, Atomic physics
Specific Effect of Peculiar Velocities on Dark-energy Constraints from Type Ia Supernovae. Peculiar velocities of Type Ia supernova (SN Ia) host galaxies affect the dark-energy parameter constraints in a small but very specific way: the parameters are biased in a single direction in parameter space that is a priori knowable for a given SN Ia data set. We demonstrate the latter fact with a combination of inference from a cosmological N-body simulation with overwhelming statistics applied to the Pantheon SN Ia data set, then confirm it by simple quantitative arguments. We quantify small modifications to the current analyses that would ensure that the effect of cosmological parameters is essentially guaranteed to be negligible.

Keywords: Galaxy radial velocities, Type Ia supernovae, Dark energy
A Gamma-Ray Periodic Modulation in Globular Cluster 47 Tucanae. The globular cluster 47 Tucanae was first detected in gamma rays by the Large Area Telescope (LAT) on board the Fermi Gamma-ray Space Telescope, and the gamma-ray emission has been widely attributed to the millisecond pulsars. In this work, we analyze the Fermi-LAT pass 8 data ranging from 2008 August to 2017 May and report the detection of a modulation with a period of 18.416 ± 0.008 hr at a significance level of ∼4.8σ. This is the first time detecting a significant modulation with a period much longer than that of millisecond pulsars in gamma rays from globular clusters. The periodic modulation signal appears in the Swift Burst Alert Telescope (BAT) data as well. The phase-folded Chandra X-ray light curve of a point source may have provided an additional clue.

Keywords: Globular star clusters, Binary pulsars, Gamma-rays, Periodic orbit
Turbulence Characteristics of Switchback and Nonswitchback Intervals Observed by Parker Solar Probe. We use Parker Solar Probe (PSP) in situ measurements to analyze the characteristics of solar wind turbulence during the first solar encounter covering radial distances between 35.7R⊙ and 41.7R⊙. In our analysis we isolate so-called switchback (SB) intervals (folded magnetic field lines) from nonswitchback (NSB) intervals, which mainly follow the Parker spiral field. Using a technique based on conditioned correlation functions, we estimate the power spectra of Elsasser, magnetic, and bulk velocity fields separately in the SB and NSB intervals. In comparing the turbulent energy spectra of the two types of intervals, we find the following characteristics: (1) The decorrelation length of the backward-propagating Elsasser field z- is larger in the NSB intervals than the one in the SB intervals; (2) the magnetic power spectrum in SB intervals is steeper, with spectral index close to -5/3, than in NSB intervals, which have a spectral index close to -3/2; (3) both SB and NSB turbulence are imbalanced with NSB having the largest cross-helicity, (4) the residual energy is larger in the SB intervals than in NSB, and (5) the analyzed fluctuations are dominated by Alfvénic fluctuations that are propagating in the sunward (antisunward) direction for the SB (NSB) turbulence. These observed features provide further evidence that the switchbacks observed by PSP are associated with folded magnetic field lines giving insight into their turbulence nature.

Keywords: Space plasmas, Magnetohydrodynamics, Heliosphere, Plasma physics, Interplanetary turbulence, Solar wind, Alfven waves
Discovery of Two Einstein Crosses from Massive Post-blue Nugget Galaxies at z &gt; 1 in KiDS. We report the discovery of two Einstein Crosses (ECs) in the footprint of the Kilo-Degree Survey (KiDS): KIDS J232940-340922 and KIDS J122456+005048. Using integral field spectroscopy from the Multi Unit Spectroscopic Explorer at the Very Large Telescope, we confirm their gravitational-lens nature. In both cases, the four spectra of the source clearly show a prominence of absorption features, hence revealing an evolved stellar population with little star formation. The lensing model of the two systems, assuming a singular isothermal ellipsoid (SIE) with external shear, shows that: (1) the two crosses, located at redshift z = 0.38 and 0.24, have Einstein radius RE = 5.2 kpc and 5.4 kpc, respectively; (2) their projected dark matter fractions inside the half effective radius are 0.60 and 0.56 (Chabrier initial mass function); (3) the sources are ultra-compact galaxies, Re ∼ 0.9 kpc (at redshift, zs = 1.59) and Re ∼ 0.5 kpc (zs = 1.10), respectively. These results are unaffected by the underlying mass density assumption. Due to size, blue color, and absorption-dominated spectra, corroborated by low specific star formation rates derived from optical-near-infrared spectral energy distribution fitting, we argue that the two lensed sources in these ECs are blue nuggets migrating toward their quenching phase. * Based on observations with OmegaCam@VST and MUSE@VLT (Prog. ID: 0105.A-0253).

Keywords: Galaxy formation, Strong gravitational lensing, Gravitational lensing, Dark matter
Constraining the Gravitational Lensing of z ≳ 6 Quasars from Their Proximity Zones. Since their discovery 20 years ago, the observed luminosity function of z ≳ 6 quasars has been suspected to be biased by gravitational lensing. Apart from the recent discovery of UHS J0439+1634 at z ≍ 6.52, no other strongly lensed z ≳ 6 quasar has been conclusively identified. The hyperluminous z ≍ 6.33 quasar SDSS J0100+2802, believed to host a supermassive black hole of ∼1010 M☉, has recently been claimed to be lensed by a factor of ∼450, which would negate both its extreme luminosity and black hole mass. However, its Lyα-transparent proximity zone is the largest known at z &gt; 6, suggesting an intrinsically extreme ionizing luminosity. Here we show that the lensing hypothesis of z ≳ 6 quasars can be quantitatively constrained by their proximity zones. We first show that our proximity zone analysis can recover the strongly lensed nature of UHS J0439+1634, with an estimated magnification $\mu ={28.0}_{-11.7}^{+18.4}{(}_{-18.3}^{+44.9})$ at 68% (95%) credibility that is consistent with previously published lensing models. We then show that the large proximity zone of SDSS J0100+2802 rules out lensing magnifications of μ &gt; 4.9 at 95% probability, and conclusively rule out the proposed μ &gt; 100 scenario. Future proximity zone analyses of existing z ≳ 6 quasar samples have the potential to identify promising strongly lensed candidates, constrain the distribution of z ≳ 6 quasar lensing, and improve our knowledge of the shape of the intrinsic quasar luminosity function.

Keywords: Strong gravitational lensing, Quasar absorption line spectroscopy
Kinetic Simulations of Cosmic-Ray-modified Shocks. I. Hydrodynamics. Collisionless plasma shocks are efficient sources of nonthermal particle acceleration in space and astrophysical systems. We use hybrid (kinetic ion—fluid electron) simulations to examine the nonlinear feedback of the self-generated energetic particles (cosmic rays, CRs) on the shock hydrodynamics. When CR acceleration is efficient, we find evidence of both an upstream precursor, where the inflowing plasma is compressed and heated, and a downstream postcursor, where the energy flux in CRs and amplified magnetic fields play a dynamical role. For the first time, we assess how nonlinear magnetic fluctuations in the postcursor preferentially travel away from the shock at roughly the local Alfvén speed with respect to the downstream plasma. The drift of both magnetic and CR energy with respect to the thermal plasma substantially increases the shock compression ratio with respect to the standard prediction, in particular exceeding 4 for strong shocks. Such modifications also have implications for the spectrum of the particles accelerated via diffusive shock acceleration, a significant result detailed in a companion paper.

Keywords: Plasma physics, Plasma astrophysics, Supernova remnants, Galaxy groups, Shocks, Supernovae, Cosmic rays
Kinetic Simulations of Cosmic-Ray-modified Shocks. II. Particle Spectra. Diffusive shock acceleration is a prominent mechanism for producing energetic particles in space and in astrophysical systems. Such energetic particles have long been predicted to affect the hydrodynamic structure of the shock, in turn leading to CR spectra flatter than the test-particle prediction. However, in this work along with a companion paper, we use self-consistent hybrid (kinetic ion-fluid electron) simulations to show for the first time how CR-modified shocks actually produce steeper spectra. The steepening is driven by the enhanced advection of CRs embedded in magnetic turbulence downstream of the shock, in what we call the "postcursor." These results are consistent with multiwavelength observations of supernovae and supernova remnants and have significant phenomenological implications for space/astrophysical shocks in general.

Keywords: Plasma physics, Plasma astrophysics, Galactic cosmic rays, Supernova remnants, Shocks, Supernovae, Cosmic rays
Simultaneous Multicolor Observations of Starlink's Darksat by the Murikabushi Telescope with MITSuME. In this paper, we present the SDSS g'-, the Cousins Rc-, and Ic-band magnitudes and associated colors of Starlink's STARLINK-1113 (one of the standard Starlink satellites) and 1130 (Darksat) with a darkening treatment to its surface. Using the 105 cm Murikabushi telescope/MITSuME, simultaneous multicolor observations for the above satellites were conducted four times: on 2020 April 10 and May 18 (for Darksat), and 2020 June 11 (for Darksat and STARLINK-1113). We found that (1) the SDSS g'-band apparent magnitudes of Darksat (6.95 ± 0.11-7.65 ± 0.11 mag) are comparable to or brighter than that of STARLINK-1113 (7.69 ± 0.16 mag), (2) the shorter the observed wavelength is, the fainter the satellite magnitudes tend to become, (3) the reflected flux by STARLINK-1113 is extremely (&gt;1.0 mag) redder than that of Darksat, (4) there is no clear correlation between the solar phase angle and orbital altitude-scaled magnitude, and (5) by flux model fitting of the satellite trails with the blackbody radiation, it is found that the albedo of Darksat is about half that of STARLINK-1113. In particular, result (1) is inconsistent with previous studies. However, considering both solar and observer phase angles and atmospheric extinction, the brightness of STARLINK-1113 can be drastically reduced in the SDSS g' and the Cousins Rc band. Simultaneous multicolor-multispot observations of more than three colors would give us more detailed information regarding the impact of low-Earth-orbit satellite constellations.

Keywords: Observatories, Astronomical site protection, Astronomical research
First Results from SMAUG: The Need for Preventative Stellar Feedback and Improved Baryon Cycling in Semianalytic Models of Galaxy Formation. Semianalytic models (SAMs) are a promising means of tracking the physical processes associated with galaxy formation, but many of their approximations have not been rigorously tested. As part of the Simulating Multiscale Astrophysics to Understand Galaxies project, we compare predictions from the FIRE-2 hydrodynamical "zoom-in" simulations to those from the Santa Cruz SAM run on the same halo merger trees, with an emphasis on the global mass flow cycle. Our study includes 13 halos spanning low-mass dwarfs (Mvir ∼ 1010M⊙ at z = 0), intermediate-mass dwarfs (Mvir ∼ 1011M⊙), and Milky Way-mass galaxies (Mvir ∼ 1012M⊙). The SAM and FIRE-2 predictions agree relatively well with each other in terms of stellar and interstellar medium mass but differ dramatically on circumgalactic medium mass (the SAM is lower than FIRE-2 by ∼3 orders of magnitude for dwarfs). Strikingly, the SAM predicts higher gas accretion rates for dwarfs compared to FIRE-2 by factors of ∼10-100, and this is compensated for with higher mass outflow rates in the SAM. We argue that the most severe model discrepancies are caused by the lack of preventative stellar feedback and the assumptions for halo gas cooling and recycling in the SAM. As a first step toward resolving these model tensions, we present a simple yet promising new preventative stellar feedback model in which the energy carried by supernova-driven winds is allowed to heat some fraction of gas outside of halos to at least the virial temperature such that accretion is suppressed.

Keywords: Galactic winds, Galaxy formation, Galaxy dark matter halos, Hydrodynamical simulations, Dwarf galaxies, Analytical mathematics, Star formation, Galaxy evolution, Circumgalactic medium
Five New Post-main-sequence Debris Disks with Gaseous Emission. Observations of debris disks, the products of the collisional evolution of rocky planetesimals, can be used to trace planetary activity across a wide range of stellar types. The most common end points of stellar evolution are no exception, as debris disks have been observed around several dozen white dwarf stars. But instead of planetary formation, post-main-sequence debris disks are a signpost of planetary destruction, resulting in compact debris disks from the tidal disruption of remnant planetesimals. In this work, we present the discovery of five new debris disks around white dwarf stars with gaseous debris in emission. All five systems exhibit excess infrared radiation from dusty debris, emission lines from gaseous debris, and atmospheric absorption features indicating ongoing accretion of metal-rich debris. In four of the systems, we detect multiple metal species in emission, some of which occur at strengths and transitions previously unseen in debris disks around white dwarf stars. Our first year of spectroscopic follow-up hints at strong variability in the emission lines that can be studied in the future, expanding the range of phenomena these post-main-sequence debris disks exhibit.

Keywords: Planetesimals, White dwarf stars, Debris disks, Circumstellar disks
Exploring the Perturbed Milky Way Disk and the Substructures of the Outer Disk. The recent discovery of a spiral feature in the Z - VZ phase plane in the solar neighborhood implies that the galactic disk has been remarkably affected by a dwarf galaxy passing through it some hundreds of millions of years ago. Using 429,500 Large Sky Area Multi-Object Fibre Spectroscopic Telescope K giants stars, we show that the spiral feature exists not only in the solar vicinity but it also extends to about 15 kpc from the Galactic center and then disappears beyond this radius. Moreover, we find that when the spiral features in a plot of Vφ as a function of position in the Z - VZ plane at various galactocentric radii are remapped to the R - Z plane, the spiral can explain well the observed asymmetric velocity substructures. This is evidence that the phase spiral features are the same as the bulk motions found in previous work as well as this work. Test particle simulations and N-body simulations show that an encounter with a dwarf galaxy a few hundred million years ago will induce a perturbation in the galactic disk. In addition, we find that the last impact of Sgr dSph can also contribute to the flare. As a consequence of the encounter, the distribution function of disk stars at a large range of radii is imprinted by the gravitational perturbation.

Keywords: Milky Way disk
Near-infrared and Optical Continuum Emission Region Size Measurements in the Gravitationally lensed Quasars Q0957+561 and SBS0909+532. We present a microlensing analysis of updated light curves in three filters, the g-band, r-band, and H-band, for the gravitationally lensed quasars Q0957+561 and SBS0909+532. Both systems display prominent microlensing features which we analyze using our Bayesian Monte Carlo technique to constrain the quasar continuum emission region sizes in each band. We report sizes as half-light radii scaled to a 60° inclination angle. For Q0957+561 we measure $\mathrm{log}({r}_{1/2}/\mathrm{cm})={16.54}_{-0.33}^{+0.33}$ , ${16.66}_{-0.62}^{+0.37}$ , and ${17.37}_{-0.40}^{+0.49}$ in g-, r-, and H-band, respectively. For SBS0909+532 we measure $\mathrm{log}({r}_{1/2}/\mathrm{cm})={15.83}_{-0.33}^{+0.33}$ , ${16.21}_{-0.62}^{+0.37}$ , and ${17.90}_{-0.63}^{+0.61}$ in the g-, r-, and H-band respectively. With size measurements in three bands spanning the quasar rest frame ultraviolet to optical, we can place constraints on the scaling of accretion disk size with wavelength, $r\propto {\lambda }^{1/\beta }$ . In a joint analysis of both systems we find a slope shallower than that predicted by thin disk theory, $\beta ={0.35}_{-0.08}^{+0.16}$ , consistent with other constraints from multi-epoch microlensing studies.

Keywords: Quasar microlensing, Gravitational lensing, Quasars, Gravitational microlensing