Sazuna/UAT_keywords huggingface dataset:
Evidence of Stellar Oscillations in the Post-common-envelope Binary Candidate ASASSN-V J205543.90+240033.5. ASASSN-V J205543.90+240033.5 (ASJ2055) is a possible post-common-envelope binary system. Its optical photometric data show an orbital variation of about 0.52 days and a fast period modulation of P 0 ~ 9.77 minutes, whose origin is unknown. In this Letter, we report evidence of the stellar oscillation of the companion star as the origin of the fast period modulation. We analyze the photometric data taken by the Transiting Exoplanet Survey Satellite, the Liverpool Telescope, and the Lulin One-meter Telescope. It is found that the period of the 9.77 minutes signal measured in 2022 August is significantly shorter than that in 2021 July/August, and the magnitude of the change is of the order of ∣△P 0∣/P 0 ~ 0.0008(4). Such a large variation will be incompatible with the scenario of the white dwarf (WD) spin as the origin of the 9.77 minutes periodic modulation. We suggest that the fast periodic signal is related to the emission from the irradiated companion star rather than that of the WD. Using existing photometric data covering a wide wavelength range, we estimate that the hot WD in ASJ2055 has a temperature of T eff ~ 80,000 K and is heating the oscillating M-type main-sequence star with T eff ~ 3500 K on its unirradiated surface. The stellar oscillation of the M-type main-sequence star has been predicted in theoretical studies, but no observational confirmation has been done. ASJ2055, therefore, has the potential to be a unique laboratory for investigating the stellar oscillation of an M-type main-sequence star and the heating effect on stellar oscillation.

Keywords: White dwarf stars, Binary stars
SN 2022acko: The First Early Far-ultraviolet Spectra of a Type IIP Supernova. We present five far- and near-ultraviolet spectra of the Type II plateau supernova, SN 2022acko, obtained 5, 6, 7, 19, and 21 days after explosion, all observed with the Hubble Space Telescope/Space Telescope Imaging Spectrograph. The first three epochs are earlier than any Type II plateau supernova has been observed in the far-ultraviolet revealing unprecedented characteristics. These three spectra are dominated by strong lines, primarily from metals, which contrasts with the featureless early optical spectra. The flux decreases over the initial time series as the ejecta cool and line blanketing takes effect. We model this unique data set with the non-local thermodynamic equilibrium radiation transport code CMFGEN, finding a good match to the explosion of a low-mass red supergiant with energy E kin = 6 × 1050 erg. With these models we identify, for the first time, the ions that dominate the early ultraviolet spectra. We present optical photometry and spectroscopy, showing that SN 2022acko has a peak absolute magnitude of V = - 15.4 mag and plateau length of ~115 days. The spectra closely resemble those of SN 2005cs and SN 2012A. Using the combined optical and ultraviolet spectra, we report the fraction of flux as a function of bluest wavelength on days 5, 7, and 19. We create a spectral time-series of Type II supernovae in the ultraviolet, demonstrating the rapid decline of flux over the first few weeks of evolution. Future observations of Type II supernovae are required to map out the landscape of exploding red supergiants, with and without circumstellar material, which is best revealed in high-quality ultraviolet spectra.

Keywords: Ultraviolet astronomy, Type II supernovae, Ultraviolet transient sources, Core-collapse supernovae
ExoGemS Detection of a Metal Hydride in an Exoplanet Atmosphere at High Spectral Resolution. Exoplanet atmosphere studies are often enriched by synergies with brown dwarf analogs. However, many key molecules commonly seen in brown dwarfs have yet to be confirmed in exoplanet atmospheres. An important example is chromium hydride (CrH), which is often used to probe atmospheric temperatures and classify brown dwarfs into spectral types. Recently, tentative evidence for CrH was reported in the low-resolution transmission spectrum of the hot Jupiter WASP-31b. Here, we present high spectral resolution observations of WASP-31b's transmission spectrum from GRACES/Gemini North and UVES/Very Large Telescope. We detect CrH at 5.6σ confidence, representing the first metal hydride detection in an exoplanet atmosphere at high spectral resolution. Our findings constitute a critical step in understanding the role of metal hydrides in exoplanet atmospheres.

Keywords: High resolution spectroscopy, Exoplanets, Exoplanet atmospheres, Transmission spectroscopy
First Glycine Isomer Detected in the Interstellar Medium: Glycolamide (NH<SUB>2</SUB>C(O)CH<SUB>2</SUB>OH). We report the first detection in the interstellar medium (ISM) of a C2H5O2N isomer: syn-glycolamide (NH2C(O)CH2OH). The exquisite sensitivity at sub-mK levels of an ultradeep spectral survey carried out with the Yebes 40 m and IRAM 30 m telescopes toward the G+0.693-0.027 molecular cloud has allowed us to unambiguously identify multiple transitions of this species. We derived a column density of (7.4 ± 0.7) × 1012 cm-2, which implies a molecular abundance with respect to H2 of 5.5 × 10-11. The other C2H5O2N isomers, including the higher-energy anti conformer of glycolamide and two conformers of glycine, were not detected. The upper limit derived for the abundance of glycine indicates that this amino acid is surely less abundant than its isomer glycolamide in the ISM. The abundances of the C2H5O2N isomers cannot be explained in terms of thermodynamic equilibrium; thus, chemical kinetics need to be invoked. While the low abundance of glycine might not be surprising, based on the relative low abundances of acids in the ISM compared to other compounds (e.g., alcohols, aldehydes, or amines), several chemical pathways can favor the formation of its isomer glycolamide. It can be formed through radical-radical reactions on the surface of dust grains. The abundances of these radicals can be significantly boosted in an environment affected by a strong ultraviolet field induced by cosmic rays, such as that expected in G+0.693-0.027. Therefore, as shown by several recent molecular detections toward this molecular cloud, it stands out as the best target to discover new species with carbon, oxygen, and nitrogen with increasing chemical complexity.

Keywords: Astrochemistry
DELVE 6: An Ancient, Ultra-faint Star Cluster on the Outskirts of the Magellanic Clouds. We present the discovery of DELVE 6, an ultra-faint stellar system identified in the second data release of the DECam Local Volume Exploration (DELVE) survey. Based on a maximum-likelihood fit to its structure and stellar population, we find that DELVE 6 is an old (τ &gt; 9.8 Gyr at 95% confidence) and metal-poor ([Fe/H] &lt; -1.17 dex at 95% confidence) stellar system with an absolute magnitude of ${M}_{V}=-{1.5}_{-0.6}^{+0.4}$ mag and an azimuthally averaged half-light radius of ${r}_{1/2}={10}_{-3}^{+4}$ pc. These properties are consistent with the population of ultra-faint star clusters uncovered by recent surveys. Interestingly, DELVE 6 is located at an angular separation of ~10° from the center of the Small Magellanic Cloud (SMC), corresponding to a 3D physical separation of ~20 kpc given the system's observed distance (D ⊙ = 80 kpc). This also places the system ~35 kpc from the center of the Large Magellanic Cloud (LMC), lying within recent constraints on the size of the LMC's dark matter halo. We tentatively measure the proper motion of DELVE 6 using data from Gaia, which we find supports a potential association between the system and the LMC/SMC. Although future kinematic measurements will be necessary to determine its origins, we highlight that DELVE 6 may represent only the second or third ancient (τ &gt; 9 Gyr) star cluster associated with the SMC, or one of fewer than two dozen ancient clusters associated with the LMC. Nonetheless, we cannot currently rule out the possibility that the system is a distant Milky Way halo star cluster.

Keywords: Magellanic Clouds, Sky surveys, Star clusters
First Detection of X-Ray Polarization from the Accreting Neutron Star 4U 1820-303. This paper reports the first detection of polarization in the X-rays for atoll-source 4U 1820-303, obtained with the Imaging X-ray Polarimetry Explorer (IXPE) at 99.999% confidence level (CL). Simultaneous polarimetric measurements were also performed in the radio with the Australia Telescope Compact Array. The IXPE observations of 4U 1820-303 were coordinated with Swift X-ray Telescope, Neutron Star Interior Composition Explorer, and Nuclear Spectroscopic Telescope Array aiming to obtain an accurate X-ray spectral model covering a broad energy interval. The source shows a significant polarization above 4 keV, with a polarization degree of 2.0% ± 0.5% and a polarization angle of -55° ± 7° in the 4-7 keV energy range, and a polarization degree of 10% ± 2% and a polarization angle of -67° ± 7° in the 7-8 keV energy bin. This polarization also shows a clear energy trend with polarization degree increasing with energy and a hint for a position-angle change of ≃90° at 96% CL around 4 keV. The spectro-polarimetric fit indicates that the accretion disk is polarized orthogonally to the hard spectral component, which is presumably produced in the boundary/spreading layer. We do not detect linear polarization from the radio counterpart, with a 3σ upper limit of 50% at 7.25 GHz.

Keywords: Neutron stars, Stellar accretion disks, Spectropolarimetry, Low-mass x-ray binary stars, Polarimetry
Evidence of a Massive Stellar Disruption in the X-Ray Spectrum of ASASSN-14li. The proximity and duration of the tidal disruption event ASASSN-14li led to the discovery of narrow, blueshifted absorption lines in X-rays and UV. The gas seen in X-ray absorption is consistent with bound material close to the apocenter of elliptical orbital paths, or with a disk wind similar to those seen in Seyfert-1 active galactic nuclei. We present a new analysis of the deepest high-resolution XMM-Newton and Chandra spectra of ASASSN-14li. Driven by the relative strengths of He-like and H-like charge states, the data require [N/C] ≥ 2.4, in qualitative agreement with UV spectral results. Flows of the kind seen in the X-ray spectrum of ASASSN-14li were not clearly predicted in simulations of TDEs; this left open the possibility that the observed absorption might be tied to gas released in prior active galactic nucleus (AGN) activity. However, the abundance pattern revealed in this analysis points to a single star rather than a standard AGN accretion flow comprised of myriad gas contributions. The simplest explanation of the data is likely that a moderately massive star (M ≳ 3 M ☉) with significant CNO processing was disrupted. An alternative explanation is that a lower mass star was disrupted that had previously been stripped of its envelope. We discuss the strengths and limitations of our analysis and these interpretations.

Keywords: Black hole physics, High energy astrophysics
Confirmation of Subsolar Metallicity for WASP-77Ab from JWST Thermal Emission Spectroscopy. We present the dayside thermal emission spectrum of WASP-77Ab from 2.8 to 5.2 μm as observed with the NIRSpec instrument on the James Webb Space Telescope (JWST). WASP-77Ab was previously found to have a subsolar metallicity and a solar carbon-to-oxygen (C/O) ratio from H2O and CO absorption lines detected using high-resolution spectroscopy. By performing atmospheric retrievals on the JWST spectrum assuming chemical equilibrium, we find a subsolar metallicity [M/H] = $-{0.91}_{-0.16}^{+0.24}$ and C/O ratio ${0.36}_{-0.09}^{+0.10}$ . We identify H2O and CO and constrain their abundances, and we find no CO2 in the spectrum. The JWST and high-resolution spectroscopy results agree within ~1σ for the metallicity and within 1.8σ for the C/O ratio. However, our results fit less well in the picture painted by the shorter wavelength spectrum measured by Hubble Space Telescope Wide Field Camera 3. Comparing the JWST thermal emission spectra of WASP-77Ab and HD 149026b shows that both hot Jupiters have nearly identical brightness temperatures in the near-infrared but distinctly different atmospheric compositions. Our results reaffirm high-resolution spectroscopy as a powerful and reliable method to measure molecular abundances. Our results also highlight the incredible diversity of hot Jupiter atmospheric compositions.

Keywords: Exoplanet atmospheres, Exoplanets, James Webb Space Telescope
Outflowing Helium from a Mature Mini-Neptune. We announce the detection of escaping helium from TOI 2134b, a mini-Neptune a few gigayears old. The average in-transit absorption spectrum shows a peak of 0.37% ± 0.05% and an equivalent width of W avg = 3.3 ± 0.3 mÅ. Among all planets with helium detections, TOI 2134b is the only mature mini-Neptune, has the smallest helium signal, and experiences the lowest X-ray and ultraviolet (XUV) flux. Putting TOI 2134b in the context of all other helium detections, we report the detection of a strong (p = 3.0 × 10-5) and theoretically expected correlation between F XUV/ρ XUV (proportional to the energy-limited mass-loss rate) and R * W avg (roughly proportional to the observationally inferred mass-loss rate). Here W avg is the equivalent width of the helium absorption, and ρ XUV is the density of the planet within the XUV photosphere, but the correlation is similarly strong if we use the optical photosphere. Having the lowest value on both axes, TOI 2134b anchors the relation. We encourage further observations to fill in the missing regions of this parameter space and improve estimates of F XUV.

Keywords: Mini Neptunes, Exoplanet atmospheres, Exoplanet atmospheric evolution
First Results from the JWST Early Release Science Program Q3D: Benchmark Comparison of Optical and Mid-infrared Tracers of a Dusty, Ionized Red Quasar Wind at z = 0.435. The [O III] 5007 Å emission line is the most common tracer of warm, ionized outflows in active galactic nuclei across cosmic time. JWST newly allows us to use mid-IR spectral features at both high spatial and spectral resolution to probe these same winds. Here we present a comparison of ground-based, seeing-limited [O III] and space-based, diffraction-limited [S IV] 10.51 μm maps of the powerful, kiloparsec-scale outflow in the Type 1 red quasar SDSS J110648.32+480712.3. The JWST data are from the Mid-InfraRed Instrument. There is a close match in resolution between the data sets (~0.″6), in ionization potential of the O+2 and S+3 ions (35 eV) and in line sensitivity (1-2 × 10-17 erg s-1 cm-2 arcsec-2). The [O III] and [S IV] line shapes match in velocity and line width over much of the 20 kpc outflowing nebula, and [S IV] is the brightest line in the rest-frame 3.5-19.5 μm range, demonstrating its usefulness as a mid-IR probe of quasar outflows. [O III] is nevertheless intrinsically brighter and provides better contrast with the point-source continuum, which is strong in the mid-IR. There is a strong anticorrelation of [O III]/[S IV] with average velocity, which is consistent with a scenario of differential obscuration between the approaching (blueshifted) and receding (redshifted) sides of the flow. The dust in the wind may also obscure the central quasar, consistent with models that attribute red quasar extinction to dusty winds.

Keywords: Galaxy winds, Quasars
Deuterium Escape on Photoevaporating Sub-Neptunes. We investigate the evolution of the deuterium-to-hydrogen (D/H) mass ratio driven by EUV photoevaporation of hydrogen-rich atmospheres of close-in sub-Neptunes around solar-type stars. For the first time, the diffusion-limited approach in conjunction with energy-limited photoevaporation is considered in evaluating deuterium escape from evolving exoplanet H/He envelopes. We find that the planets with smaller initial gas envelopes and thus smaller sizes can lead to weaker atmospheric escape, which facilitates hydrogen-deuterium fractionation. Specifically, in our grid of simulations with a low envelope mass fraction of less than 0.005, a low-mass sub-Neptune (4-5 M ⊕) at about 0.25-0.4 au or a high-mass sub-Neptune (10-15 M ⊕) at about 0.1-0.25 au can increase the D/H values by greater than 20% over 7.5 Gyr. Akin to the helium-enhanced envelopes of sub-Neptunes due to photoevaporating escape, the planets along the upper boundary of the radius valley are the best targets to detect high D/H ratios. The ratio can rise by a factor of ≲1.65 within 7.5 Gyr in our grid of evolutionary calculations. The D/H ratio is expected to be higher in thinner envelopes as long as the planets do not become bare rocky cores.

Keywords: Exoplanet atmospheric composition , Mini Neptunes, Exoplanets, Exoplanet atmospheric evolution
IXPE and Multiwavelength Observations of Blazar PG 1553+113 Reveal an Orphan Optical Polarization Swing. The lower-energy peak of the spectral energy distribution of blazars has commonly been ascribed to synchrotron radiation from relativistic particles in the jets. Despite the consensus regarding jet emission processes, the particle acceleration mechanism is still debated. Here, we present the first X-ray polarization observations of PG 1553+113, a high-synchrotron-peak blazar observed by the Imaging X-ray Polarimetry Explorer (IXPE). We detect an X-ray polarization degree of (10 ± 2)% along an electric-vector position angle of ψ X = 86° ± 8°. At the same time, the radio and optical polarization degrees are lower by a factor of ~3. During our IXPE pointing, we observed the first orphan optical polarization swing of the IXPE era, as the optical angle of PG 1553+113 underwent a smooth monotonic rotation by about 125°, with a rate of ~17° day-1. We do not find evidence of a similar rotation in either radio or X-rays, which suggests that the X-ray and optically emitting regions are separate or, at most, partially cospatial. Our spectropolarimetric results provide further evidence that the steady-state X-ray emission in blazars originates in a shock-accelerated and energy-stratified electron population.

Keywords: Spectropolarimetry, Jets, BL Lacertae objects, Active galactic nuclei, X-ray active galactic nuclei, Polarimetry
A CEERS Discovery of an Accreting Supermassive Black Hole 570 Myr after the Big Bang: Identifying a Progenitor of Massive z &gt; 6 Quasars. We report the discovery of an accreting supermassive black hole at z = 8.679. This galaxy, denoted here as CEERS_1019, was previously discovered as a Lyα-break galaxy by Hubble with a Lyα redshift from Keck. As part of the Cosmic Evolution Early Release Science (CEERS) survey, we have observed this source with JWST/NIRSpec, MIRI, NIRCam, and NIRCam/WFSS and uncovered a plethora of emission lines. The Hβ line is best fit by a narrow plus a broad component, where the latter is measured at 2.5σ with an FWHM ~1200 km s-1. We conclude this originates in the broadline region of an active galactic nucleus (AGN). This is supported by the presence of weak high-ionization lines (N V, N IV], and C III]), as well as a spatial point-source component. The implied mass of the black hole (BH) is log (M BH/M ⊙) = 6.95 ± 0.37, and we estimate that it is accreting at 1.2 ± 0.5 times the Eddington limit. The 1-8 μm photometric spectral energy distribution shows a continuum dominated by starlight and constrains the host galaxy to be massive (log M/M⊙ ~9.5) and highly star-forming (star formation rate, or SFR ~ 30 M⊙ yr-1; log sSFR ~ - 7.9 yr-1). The line ratios show that the gas is metal-poor (Z/Z ⊙ ~ 0.1), dense (n  e  ~ 103 cm-3), and highly ionized (log U ~ - 2.1). We use this present highest-redshift AGN discovery to place constraints on BH seeding models and find that a combination of either super-Eddington accretion from stellar seeds or Eddington accretion from very massive BH seeds is required to form this object.

Keywords: AGN host galaxies, Observational astronomy, Black holes, Infrared spectroscopy, Spectroscopy, High-redshift galaxies, Galaxies
Hadronic versus Leptonic Origin of Gamma-Ray Emission from Supernova Remnants. GeV and TeV emission from the forward shocks of supernova remnants (SNRs) indicates that they are capable particle accelerators, making them promising sources of Galactic cosmic rays (CRs). However, it remains uncertain whether this γ-ray emission arises primarily from the decay of neutral pions produced by very-high-energy hadrons, or from inverse-Compton and/or bremsstrahlung emission from relativistic leptons. By applying a semi-analytic approach to non-linear diffusive shock acceleration, and calculating the particle and photon spectra produced in different environments, we parameterize the relative strength of hadronic and leptonic emission. We show that even if CR acceleration is likely to occur in all SNRs, the observed photon spectra may primarily reflect the environment surrounding the SNR: the emission is expected to look hadronic unless the ambient density is particularly low (with proton number density ≲0.1 cm-3) or the photon background is enhanced with respect to average Galactic values (with radiation energy density u rad ≳ 10 eV cm-3). We introduce a hadronicity parameter to characterize how hadronic or leptonic we expect a source to look based on its environment, which can be used to guide the interpretation of current γ-ray observations and the detection of high-energy neutrinos from SNRs.

Keywords: High-energy cosmic radiation, Cosmic ray astronomy, Galactic cosmic rays, Supernova remnants, Cosmic ray sources, Shocks
Mass Dependence of Galaxy-Halo Alignment in LOWZ and CMASS. We measure the galaxy-ellipticity (GI) correlations for the Sloan Digital Sky Survey Data Release 12 LOWZ and CMASS samples with the shape measurements from the DESI Legacy Imaging Surveys. We model the GI correlations in an N-body simulation with our recent accurate stellar-halo mass relation from the Photometric object Around Cosmic webs (PAC) method. The large data set and our accurate modeling turns out an accurate measurement of the alignment angle between central galaxies and their host halos. We find that the alignment of central elliptical galaxies with their host halos increases monotonically with galaxy stellar mass or host halo mass, which can be well described by a power law for the massive galaxies. We also find that central elliptical galaxies are more aligned with their host halos in LOWZ than in CMASS, which might indicate an evolution of galaxy-halo alignment, though future studies are needed to verify this is not induced by the sample selections. In contrast, central disk galaxies are aligned with their host halos about 10 times more weakly in the GI correlation. These results have important implications for intrinsic alignment (IA) correction in weak lensing studies, IA cosmology, and theory of massive galaxy formation.

Keywords: Weak gravitational lensing, Galaxy dark matter halos, Galaxy properties, Large-scale structure of the universe