adsabs/SciX_UAT_keywords huggingface dataset:
Exploring the Properties of Photosphere and Emission Lines for Tidal Disruption Events Based on the Global Solution of Slim Disk and Winds

The theoretical debris supply rate from a tidal disruption of stars can exceed about 100 times of Eddington accretion rate for a 106‑7 M ⊙ supermassive black hole. It is believed that a strong wind will be launched from the disk surface due to the radiation pressure in the case of super-Eddington accretion, which may be one of the mechanisms for the formation of the envelope, as observed in tidal disruption events (TDEs). In this work, we explore the evolution of the envelope that formed from the optical thick winds by solving the global solution of the slim-disk model. Our model can roughly reproduce the typical temperature, luminosity, and size of the photosphere for TDEs. Based on Cloudy modeling, we find that, if only considering the radiation-driven disk wind, the emission line luminosities are normally much lower than the typical observational results, due to the limited atmosphere mass outside the envelope. We propose that the ejection of the outflow from the self-collision of the stellar debris during the circularization may provide enough matter outside the disk-wind photosphere. Our calculated spectra can roughly reproduce the main properties of several typical emission lines (e.g., Hα, Hβ, and He II), which was applied well to a TDE candidate AT2018dyb.

Keywords: black hole physics; radiative transfer; tidal disruption
Complex Reactive Acids from Methanol and Carbon Dioxide Ice: Glycolic Acid (HOCH2COOH) and Carbonic Acid Monomethyl Ester (CH3OCOOH)

The formation of complex organic molecules by simulated secondary electrons generated in the track of galactic cosmic rays was investigated in interstellar ice analogs composed of methanol and carbon dioxide. The processed ices were subjected to temperature-programmed desorption to mimic the transition of a cold molecular cloud to a warmer star-forming region. Reaction products were detected as they sublime using photoionization reflectron time-of-flight mass spectrometry. By employing isotopic labeling, tunable photoionization and computed adiabatic ionization energies isomers of C2H4O3 were investigated. Product molecules carbonic acid monomethyl ester (CH3OCOOH) and glycolic acid (HOCH2COOH) were identified. The abundance of the reactants detected in analog interstellar ices and the low irradiation dose necessary to form these products indicates that these molecules are exemplary candidates for interstellar detection. Molecules sharing a tautomeric relationship with glycolic acid, dihydroxyacetaldehyde ((OH)2CCHO), and the enol ethenetriol (HOCHC(OH)2), were not found to form despite ices being subjected to conditions that have successfully produced tautomerization in other ice analog systems.

Keywords: laboratory astrophysics; interstellar molecules; radical-radical recombination; pre-biotic astrochemistry; astrochemistry
Four-hundred Very Metal-poor Stars Studied with LAMOST and Subaru. III. Dynamically Tagged Groups and Chemodynamical Properties

Very metal-poor (VMP) stars record the signatures of early accreted galaxies, making them essential tools for unraveling the early stages of Galaxy formation. Understanding the origin of VMP stars requires comprehensive studies of their chemical compositions and kinematics, which are currently lacking. Hence, we conduct a chemodynamical analysis of 352 VMP stars selected from one of the largest uniform high-resolution VMP star samples, jointly obtained from LAMOST and Subaru. We apply a friends-of-friends clustering algorithm to the master catalog of this high-resolution sample, which consists of 5778 VMP stars. It results in 131 dynamically tagged groups with 89 associated with known substructures in the Milky Way, including Gaia-Sausage-Enceladus (GSE), Thamnos, Helmi streams, Sequoia, Wukong, Pontus, and the very metal-poor disk (VMPD). Our findings are: (i) the VMPD shows lower Zn abundances than the rest, which indicates that it could be a relic of small stellar systems; (ii) Sequoia shows moderately high r-process abundances; (iii) Helmi streams show deficiencies in carbon and light neutron-capture elements; (iv) the fraction of carbon-enhanced metal-poor stars with no enhancement in heavy elements (CEMP-no stars) seems low in the VMPD and the Helmi streams; and (v) a subgroup in GSE exhibits a very high fraction of r-process enhanced stars, with four out of five showing [Eu/Fe]> +1.0. The abundance patterns of other elements in VMP substructures largely match the whole VMP sample. We also study large-scale correlations between abundance ratios and kinematics without classifying stars into substructures, but it does not yield significant correlations once the overall chemical evolution is considered for most elements.

Keywords: milky way dynamics; milky way evolution; milky way galaxy; galaxy chemical evolution; galaxy abundances; galactic archaeology; population ii stars
Tolerance For the Pixelation Effect in Shear Measurement

Images taken by space telescopes typically have a superb spatial resolution, but a relatively poor sampling rate due to the finite CCD pixel size. Beyond the Nyquist limit, it becomes uncertain how much the pixelation effect may affect the accuracy of galaxy shape measurement. It is timely to study this issue given that a number of space-based large-scale weak lensing surveys are planned. Using the Fourier_Quad method, we quantify the shear recovery error as a function of the sampling factor Q, i.e., the ratio between the FWHM of the point-spread function (PSF) and the pixel size of the CCD, for different PSFs and galaxies of different sizes and noise levels. We show that sub-percent-level accuracy in shear recovery is achievable with single-exposure images for Q ≲ 2. The conclusion holds for galaxies much smaller than the PSF, and those with a significant level of noise.

Keywords: weak gravitational lensing; gravitational lensing shear; astronomy data analysis; space telescopes
Kinetic Imprints of Ion Acceleration in Collisionless Magnetic Reconnection

Fast collisionless magnetic reconnection implies fast energy conversion. The main form of energy conversion in magnetic reconnection concerns bulk ion acceleration with resulting ion jets. Based on theoretical analysis and MMS data, we examine the kinetic imprints of ion in the context of fast reconnection rates. The ion kinetic imprints we analyze in MMS observations include ion beams toward the X-line and distorted velocity distributions in reconnection jets. The distorted ion velocity distributions lead to a bipolar reversal in an off-diagonal element of the pressure tensor across the X-line, supporting an enhancement of the ion-scale reconnection electric field.

Keywords: planetary magnetospheres; space plasmas
Naked Forward Shock Seen in the TeV Afterglow Data of GRB 221009A

We explore the implications of the light curve of the early TeV gamma-ray afterglow of GRB 221009A reported by the LHAASO Collaboration. We show that the reported offset of the reference time, T *, allows the determination of the activation time of the main jet component, which occurs approximately 200 s after the Gamma-ray Burst Monitor (GBM) trigger time and closely precedes the moment at which GBM was saturated. We find that while the LHAASO data do not exclude the homogeneous circumburst medium scenario, the progenitor wind scenario looks preferable, finding excellent agreement with the expected size of the stellar bubble. We conclude that the initial growth of the light curve is dominated by processes internal to the jet or by gamma-gamma attenuation on the photons emitted during the prompt phase. Namely, either the activation of the acceleration process or the decrease of internal gamma-gamma absorption can naturally explain the initial rapid flux increase. The subsequent slow flux growth phase observed up to T * + 18 s can be related to the process of particle accumulation in the production region. The duration of this phase allows an almost parameter-independent determination of the jet's initial Lorentz factor, Γ0 ≈ 600, and magnetic field strength, $B^{\prime} \sim 0.3\,{\rm{G}}$ . These values appear to match well those previously revealed through spectral modeling of the GRB emission.

Keywords: gamma-rays; gamma-ray transient sources; gamma-ray bursts; gamma-ray sources
Orbits and Masses of Binaries from Speckle Interferometry at SOAR

We present results from Speckle inteferometric observations of 15 visual binaries and one double-line spectroscopic binary, carried out with the HRCam Speckle camera of the SOAR 4.1 m telescope. These systems were observed as a part of an on-going survey to characterize the binary population in the solar vicinity, out to a distance of 250 pc. We obtained orbital elements and mass sums for our sample of visual binaries. The orbits were computed using a Markov Chain Monte Carlo algorithm that delivers maximum likelihood estimates of the parameters, as well as posterior probability density functions that allow us to evaluate their uncertainty. Their periods cover a range from 5 yr to more than 500 yr; and their spectral types go from early A to mid M, implying total system masses from slightly more than 4M⊙ down to 0.2M⊙. They are located at distances between approximately 12 and 200 pc, mostly at low Galactic latitude. For the double-line spectroscopic binary YSC8, we present the first combined astrometric/radial-velocity orbit resulting from a self-consistent fit, leading to individual component masses of 0.897 ± 0.027 M⊙ and 0.857 ± 0.026 M⊙; and an orbital parallax of 26.61 ± 0.29 mas, which compares very well with the Gaia DR2 trigonometric parallax (26.55 ± 0.27 mas). In combination with published photometry and trigonometric parallaxes, we place our objects on an H-R diagram and discuss their evolutionary status. We also present a thorough analysis of the precision and consistency of the photometry available for them. * Based on observations obtained at the Southern Astrophysical Research (SOAR) telescope, which is a joint project of the Ministrio da Cincia, Tecnologia, e Inovao (MCTI) da Repblica Federativa do Brasil, the U.S. National Optical Astronomy Observatory (NOAO), the University of North Carolina at Chapel Hill (UNC), and Michigan State University (MSU).

Keywords: stellar masses; visual binary stars; speckle interferometry; astrometry; hertzsprung russell diagram; radial velocity; ccd photometry; stellar luminosities; sky surveys; interferometric binary stars; spectroscopic binary stars; stellar evolutionary tracks
True Pair-instability Supernova Descendant: Implications for the First Stars' Mass Distribution

The initial mass function (IMF) of the first Population III (Pop III) stars remains a persistent mystery. Their predicted massive nature implies the existence of stars exploding as pair-instability supernovae (PISNe), but no observational evidence had been found. Now, the LAMOST survey claims to have discovered a pure PISN descendant, J1010+2358, at [Fe/H] = ‑ 2.4. Here we confirm that a massive 250–260 M ⊙ PISN is needed to reproduce the abundance pattern of J1010+2358. However, the PISN contribution can be as low as 10%, since key elements are missing to discriminate between scenarios. We investigate the implications of this discovery for the Pop III IMF, by statistical comparison with the predictions of our cosmological galaxy formation model, NEFERTITI. First, we show that the nondetection of mono-enriched PISN descendants at [Fe/H] < ‑ 2.5 allows us to exclude (i) a flat IMF at a 90% confidence level; and (ii) a Larson-type IMF with characteristic mass m ch/M ⊙ > 191.16x ‑ 132.44, where x is the slope, at a 75% confidence level. Second, we show that if J1010+2358 has only inherited <70% of its metals from a massive PISN, no further constraints can be put on the Pop III IMF. If, instead, J1010+2358 will be confirmed to be a nearly pure (>90%) PISN descendant, it will offer strong and complementary constraints on the Pop III IMF, excluding the steepest and bottom-heaviest IMFs: m ch/M ⊙ < 143.21x ‑ 225.94. Our work shows that even a single detection of a pure PISN descendant can be crucial to our understanding of the mass distribution of the first stars.

Keywords: population iii stars; milky way evolution; galaxy evolution; galaxy formation; milky way formation; theoretical models; milky way stellar halo
An X-Ray- and SZ-bright Diffuse Source toward M31: A Local Hot Bridge

We report a large-scale ( $r\approx 20^\circ $ ) X-ray-bright and Sunyaev-Zeldovich (SZ)-bright diffuse enhancement toward M31, which might be a Local Hot Bridge connecting the Milky Way (MW) with M31. We subtract the Galactic emission from the all-sky O VII and O VIII emission-line measurement survey, and find that the emission of these two ions is enhanced within $r\approx 20^\circ $ projected around M31. The mean emission enhancements are 5.6 ± 1.3 L.U., and 2.8 ± 0.6 L.U. for O VII and O VIII, respectively ( $\gt 4\sigma $ for both ions). We also extract the SZ signal around M31, which suggests a surface brightness y of $2-4\times {10}^{-7}$ , an enhancement $\gt 2.5\sigma $ (and a best fit of $5.9\sigma $ ). These three measurements trace the hot gas with a temperature $\mathrm{log}\,T({\rm{K}})\gt 6$ , showing similar plateau shapes (flat within $\approx 15^\circ $ , and zero beyond ≈30°). A single-phase assumption leads to a temperature of $\mathrm{log}\,T({\rm{K}})=6.34\pm 0.03$ , which is determined by the O VII/O VIII line ratio. Combining X-ray and SZ measurements, we suggest that this feature is unlikely to be the hot halo around M31 (too massive) or in the MW (too high pressure and X-ray bright). The plateau shape may be explained by a cylinder connecting the MW and M31 (the Local Hot Bridge). We constrain its length to be about 400 kpc, with a radius of 120 kpc, a density of $\approx 2\times {10}^{-4}\mbox{--}{10}^{-3}\,{\mathrm{cm}}^{-3}$ , and a metallicity of $0.02\mbox{--}0.1\,{Z}_{\odot }$ . The baryon mass is $\gtrsim {10}^{11}\,{M}_{\odot }$ , and the oxygen mass is about $\gtrsim {10}^{8}\,{M}_{\odot }$ , which contribute to the baryon or metal budget of the Local Group.

Keywords: circumgalactic medium; local group; diffuse x-ray background; sunyaev-zeldovich effect
ALMA Observations toward the S-shaped Outflow and the Envelope around NGC 1333 IRAS 4A2

We have analyzed the ALMA archival data of the SO (JN = 65 - 54 and JN = 76 - 65), CO (J = 2 - 1), and CCH (N = 3 - 2, J = 7/2 - 5/2, F = 4 - 3) lines from the Class 0 protobinary system, NGC 1333 IRAS 4A. The images of SO (JN = 65 - 54) and CO (J = 2 - 1) successfully separate two northern outflow lobes connected to each protostar, IRAS 4A1 and IRAS 4A2. The outflow from IRAS 4A2 shows an S-shaped morphology, consisting of a flattened envelope around IRAS 4A2 with two outflow lobes connected to both edges of the envelope. The flattened envelope surrounding IRAS 4A2 has a velocity gradient opposite to that of the circumbinary envelope. The observed features are reproduced by the magnetohydrodynamic simulation of the collapsing core whose magnetic field direction is misaligned with the rotational axis. Our simulation shows that the intensity of the outflow lobes is enhanced on one side, resulting in the formation of S-shaped morphology. The S-shaped outflow can also be explained by the precessing outflow launched from an unresolved binary with a separation larger than 12 au (0"04). Additionally, we discovered a previously unknown extremely high-velocity component at ~45-90 km s-1 near IRAS 4A2 with CO. CCH (JN,F = 7/23,4 - 5/22,3) emission shows two pairs of blobs attached to the bottom of a shell-like feature, and the morphology is significantly different from that of the SO and CO lines. Toward IRAS 4A2, the S-shaped outflow shown in SO is overlapped with the edges of CCH shells, while CCH shells have velocity gradients opposite to those of the flattened structure around IRAS 4A2.

Keywords: star formation; stellar winds; protostars; young stellar objects; magnetohydrodynamical simulations
The Physical Conditions of Emission-line Galaxies at Cosmic Dawn from JWST/NIRSpec Spectroscopy in the SMACS 0723 Early Release Observations

We present rest-frame optical emission-line flux ratio measurements for five z > 5 galaxies observed by the James Webb Space Telescope Near-Infared Spectrograph (NIRSpec) in the SMACS 0723 Early Release Observations. We add several quality-control and post-processing steps to the NIRSpec pipeline reduction products in order to ensure reliable relative flux calibration of emission lines that are closely separated in wavelength, despite the uncertain absolute spectrophotometry of the current version of the reductions. Compared to z ~ 3 galaxies in the literature, the z > 5 galaxies have similar [O III]λ5008/Hβ ratios, similar [O III]λ4364/Hγ ratios, and higher (~0.5 dex) [Ne III]λ3870/[O II]λ3728 ratios. We compare the observations to MAPPINGS V photoionization models and find that the measured [Ne III]λ3870/[O II]λ3728, [O III]λ4364/Hγ, and [O III]λ5008/Hβ emission-line ratios are consistent with an interstellar medium (ISM) that has very high ionization ( $\mathrm{log}(Q)\simeq 8-9$ , units of cm s-1), low metallicity (Z/Z ⊙ ≲ 0.2), and very high pressure ( $\mathrm{log}(P/k)\simeq 8-9$ , units of cm-3). The combination of [O III]λ4364/Hγ and [O III]λ(4960 + 5008)/Hβ line ratios indicate very high electron temperatures of $4.1\lt \mathrm{log}({T}_{e}/{\rm{K}})\lt 4.4$ , further implying metallicities of Z/Z ⊙ ≲ 0.2 with the application of low-redshift calibrations for "T e -based" metallicities. These observations represent a tantalizing new view of the physical conditions of the ISM in galaxies at cosmic dawn.

Keywords: emission line galaxies; galaxies; high-redshift galaxies
The Awakening of a Blazar at Redshift 2.7 Temporally Coincident with the Arrival of Cospatial Neutrino Event IceCube-201221A

We report on multiwavelength studies of a blazar NVSS J171822+423948, which is identified as the low-energy counterpart of 4FGL J1718.5+4237, the unique γ-ray source known to be cospatial with the IceCube neutrino event IC-201221A. After a 12 yr long quiescent period undetected by Fermi-LAT, γ-ray activities with a tenfold flux increase emerge soon (a few tens of days) after the arrival of the neutrino. Associated optical flares in the Zwicky Transient Facility g, r, and i bands are observed together with elevated Wide-field Infrared Survey Explorer infrared fluxes. Synchronized variations suggest that both the γ-ray emission and the neutrino event are connected to the blazar. Furthermore, the optical spectrum reveals emission lines at a redshift z = 2.68 ± 0.01. Thus, it is the first candidate for a neutrino-emitting blazar at the redshift above 2. Discussions of theoretical constraints of neutrino production and comparisons with other candidates are presented.

Keywords: galaxy jets; radio loud quasars; gamma-ray sources; neutrino astronomy
The JCMT Transient Survey: Single-epoch Transients and Variability of Faint Sources

Short-duration flares at millimeter wavelengths provide unique insights into the strongest magnetic reconnection events in stellar coronae and combine with longer-term variability to introduce complications to next-generation cosmology surveys. We analyze 5.5 yr of JCMT Transient Survey 850 μm submillimeter monitoring observations toward eight Gould Belt star-forming regions to search for evidence of transient events or long-duration variability from faint sources. The eight regions (30' diameter fields), including ~1200 infrared-selected YSOs, have been observed on average 47 times with integrations of approximately half an hour, or one day total, spread over 5.5 yr. Within this large data set, only two robust faint source detections are recovered: JW 566 in OMC 2/3 and MGM12 2864 in NGC 2023. JW 566, a Class II T Tauri binary system previously identified as an extraordinary submillimeter flare, remains unique, the only clear single-epoch transient detection in this sample with a flare eight times bright than our ~4.5σ detection threshold of 55 mJy beam-1. The lack of additional recovered flares intermediate between JW 566 and our detection limit is puzzling if smaller events are more common than larger events. In contrast, the other submillimeter variable identified in our analysis, Source 2864, is highly variable on all observed timescales. Although Source 2864 is occasionally classified as a YSO, the source is most likely a blazar. The degree of variability across the electromagnetic spectrum may be used to aid source classification.

Keywords: stellar flares; variable stars; submillimeter astronomy; surveys; young stellar objects
EMPRESS. XIV. Strong High-ionization Lines of Young Galaxies at z = 0–8: Ionizing Spectra Consistent with the Intermediate-mass Black Holes with M BH ∼ 103–106 M ⊙

We present ionizing spectra estimated at 13.6–100 eV for 10 dwarf galaxies with strong high-ionization lines of He II λ4686 and [Ne V] λ3426 ([Ne IV] λ2424) at z = 0 (z = 8) that are identified in our Keck/LRIS spectroscopy and the literature (the JWST Early Release Observations program). With the flux ratios of these high-ionization lines and >10 low-ionization lines of hydrogen, helium, oxygen, neon, and sulfur, we determine ionizing spectra consisting of stellar and nonthermal power-law radiation by photoionization modeling with free parameters of nebular properties, including metallicity and ionization parameter, canceling out abundance ratio differences. We find that all of the observed flux ratios are well reproduced by the photoionization models with the power-law index α EUV of α EUV ∼ (–1) ‑ 0 and the luminosity L EUV of L EUV ∼ 1040–1042 erg s‑1 at ∼55–100 eV for six galaxies, while four galaxies include large systematics in α EUV caused by stellar radiation contamination. We then compare α EUV and L EUV of these six galaxies with those predicted by the black hole (BH) accretion disk models and find that α EUV and L EUV are similar to those of the intermediate-mass BHs (IMBHs) in BH accretion disk models, albeit with possibilities of the other scenarios. Confirming these results with a known IMBH having a mass M BH of M BH = 105.75 M ⊙, we find that four local galaxies and one z = 7.665 galaxy have ionizing spectra consistent with those of IMBHs with M BH ∼ 103–105 M ⊙.

Keywords: galaxy formation; dwarf galaxies; intermediate-mass black holes
Stable Fiber-illumination for Extremely Precise Radial Velocities with NEID

NEID is a high-resolution red-optical precision radial velocity (RV) spectrograph recently commissioned at the WIYN 3.5 m telescope at Kitt Peak National Observatory, Arizona, USA. NEID has an extremely stable environmental control system, and spans a wavelength range of 380-930 nm with two observing modes: a High Resolution mode at R ~ 112,000 for maximum RV precision, and a High Efficiency mode at R ~ 72,000 for faint targets. In this paper we present a detailed description of the components of NEID's optical fiber feed, which include the instrument, exposure meter, calibration system, and telescope fibers. Many parts of the optical fiber feed can lead to uncalibratable RV errors, which cannot be corrected for using a stable wavelength reference source. We show how these errors directly cascade down to performance requirements on the fiber feed and the scrambling system. We detail the design, assembly, and testing of each component. Designed and built from the bottom-up with a single-visit instrument precision requirement of 27 cm s-1, close attention is paid to the error contribution from each NEID subsystem. Finally, we include the lab and on-sky tests performed during instrument commissioning to test the illumination stability, and discuss the path to achieving the instrumental stability required to search for a true Earth twin around a solar-type star.

Keywords: exoplanets; radial velocity; astronomical instrumentation; spectrometers