adsabs/SciX_UAT_keywords huggingface dataset:
The Synchrotron-based Far-infrared Spectrum of Glycolaldehyde

Glycolaldehyde (GA) has been observed toward several different sources, with a broad range of rotational temperatures (8-300 K). At the high end, the temperature is comparable to the energy of the lowest vibrational states of GA, making the vibrational contribution to the partition function significant. Here, we report an analysis of the high-resolution far-infrared spectrum of GA, which features a plethora of well-resolved lines from 170-430 cm-1 (13-5 THz). We focus on the three fundamental vibrational bands in this range, i.e., the symmetric ν12 bend at 282 cm-1, and the asymmetric ν17 and ν18 torsions at 360 and 208 cm-1, respectively. We assigned 23,266 transitions to 13,999 lines within these bands, which, when combined with the previously reported microwave and millimeter-wave spectra, allowed for refinement of the vibrationally excited rotational constants, and accurate determination of their band origins. Additionally, the assignment of a number of lines in several hot bands that are significantly populated at 300 K allowed for determination of their band origins. The rotational constants reported here should be useful in searches of vibrationally excited GA toward warm sources, and the accurately determined band origins allow for refinement of the vibrational partition function, and therefore column density, for a given excitation temperature.

Keywords: interstellar medium; molecular spectroscopy; molecular physics
IGRINS RV: A Precision Radial Velocity Pipeline for IGRINS Using Modified Forward Modeling in the Near-infrared

Application of the radial velocity (RV) technique in the near-infrared is valuable because of the diminished impact of stellar activity at longer wavelengths, making it particularly advantageous for the study of late-type stars but also for solar-type objects. In this paper, we present the IGRINS RV open-source python pipeline for computing infrared RV measurements from reduced spectra taken with IGRINS, an R ≡ λ/Δλ ∼ 45,000 spectrograph with simultaneous coverage of the H band (1.49-1.80 μm) and K band (1.96-2.46 μm). Using a modified forward-modeling technique, we construct high-resolution telluric templates from A0 standard observations on a nightly basis to provide a source of common-path wavelength calibration while mitigating the need to mask or correct for telluric absorption. Telluric standard observations are also used to model the variations in instrumental resolution across the detector, including a yearlong period when the K band was defocused. Without any additional instrument hardware, such as a gas cell or laser frequency comb, we are able to achieve precisions of 26.8 m s-1 in the K band and 31.1 m s-1 in the H band for narrow-line hosts. These precisions are empirically determined by a monitoring campaign of two RV standard stars, as well as the successful retrieval of planet-induced RV signals for both HD 189733 and τ Boo A; furthermore, our results affirm the presence of the Rossiter-McLaughlin effect for HD 189733. The IGRINS RV pipeline extends another important science capability to IGRINS, with publicly available software designed for widespread use. * https://github.com/shihyuntang/igrins_rv

Keywords: exoplanet detection methods; exoplanet formation; radial velocity; near infrared astronomy; open source software; astronomy software; starspots; young stellar objects
Digging into the Interior of Hot Cores with ALMA (DIHCA). I. Dissecting the High-mass Star-forming Core G335.579-0.292 MM1

We observed the high-mass star-forming region G335.579-0.292 with the Atacama Large Millimeter/submillimeter Array (ALMA) at 226 GHz with an angular resolution of 0"3 (∼1000 au resolution at the source distance). G335.579-0.292 hosts one of the most massive cores in the Galaxy (G335-MM1). The continuum emission shows that G335-MM1 fragments into at least five sources, while molecular line emission is detected in two of the continuum sources (ALMA1 and ALMA3). We found evidence of large- and small-scale infall in ALMA1 revealed by an inverse P-Cygni profile and the presence of a blueshifted spot at the center of the first moment map of the CH3CN emission. In addition, hot gas expansion in the innermost region is unveiled by a redshifted spot in the first moment map of HDCO and (CH3)2CO (both with Eu > 1100 K). Our modeling reveals that this expansion motion originates close to the central source, likely due to reversal of the accretion flow induced by the expansion of the H II region, while infall and rotation motions originate in the outer regions. ALMA3 shows clear signs of rotation, with a rotation axis inclination with respect to the line of sight close to 90°, and a system mass (disk + star) in the range of 10-30 M⊙.

Keywords: star formation; massive stars
Toward an Understanding of the Massive Red Spiral Galaxy Formation

To understand the formation and quenching processes of local massive red spiral galaxies with M* > 1010.5 M⊙, we perform a statistical analysis of their spectroscopic and structural properties and compare them with elliptical and blue spiral galaxies of similar mass. The sample was selected from the stellar mass catalog of galaxies in SDSS DR7, according to their locations on the u - r color-stellar mass diagram. We find that red spirals harbor compact cores with high stellar mass surface densities measured by Σ1 and are bulge dominated. Particularly, the red spirals, especially their bulges, follow the Σ1-M* ridgeline for quenched galaxies. Furthermore, the red spirals show similarly large central Dn(4000), high [Mg/Fe], and dark matter halo mass to ellipticals. These results suggest that the bulges of red spirals formed within a short timescale before redshift ∼1-2 and were quenched via a fast mode, similar to ellipticals. Careful examinations of the optical morphologies reveal that ∼70% of red spirals show strong bars, rings/shells, and even merging features, which suggests that interactions or mergers might have played an important role in the formation of red spirals. In contrast, most of the massive blue spirals have completely different spectral and structural properties from red spirals. However, the blue spirals with high Σ1 ( ${{\rm{\Sigma }}}_{1}\gt {10}^{9.5}\,{M}_{\odot }\,{\mathrm{kpc}}^{-2}$ ) show similar structural and morphological properties, as well as similar halo mass and H I mass to red spirals. We discuss rejuvenation from red to blue as a possible explanation for these high-Σ1 blue spirals.

Keywords: galaxy bulges; galaxy evolution; spiral galaxies; star formation; galaxy formation; galaxy structure
The Luminosity Function of Tidal Disruption Flares for the ZTF-I Survey

The high-cadence survey of the Zwicky Transient Facility (ZTF) has completely dominated the discovery of tidal disruption events (TDEs) in the past few years and resulted in the largest sample of TDEs with optical/UV light curves well sampled around their peaks, providing us an excellent opportunity to construct a peak luminosity function (LF) of tidal disruption flares (TDFs). The new construction is necessary particularly considering that the most updated LF reported in literature has been inferred from only 13 sources from five different surveys. Here we present the optical and blackbody LFs calculated by 33 TDFs discovered in the ZTF-I survey. The optical LF can be described by both a power-law profile ${dN}/{{dL}}_{g}\propto {L}_{g}^{-2.3\pm 0.2}$ , and a Schechter-like function. The blackbody LF can be described by a power-law profile ${dN}/{{dL}}_{\mathrm{bb}}\propto {L}_{\mathrm{bb}}^{-2.2\pm 0.2}$ , shallower than the LF made of the previous van Velzen (2018) sample. A possible low-luminosity turnover in the optical LF supports an Eddington-limited emission scenario. The drop of the volumetric rate at high luminosity suggests a rate suppression due to direct captures of the black hole. The total volumetric rate is 1 order of magnitude lower than the previous estimation, which is probably not simply caused by the high fraction postpeak sources (7/13) in the previous sample. Instead, the normalization step during the previous LF construction to reconcile various surveys might adversely amplify the influence of serendipitous discoveries. Therefore, TDFs selected from ongoing and upcoming uniform surveys like ZTF, Vera Rubin Observatory, and the Wide-Field Survey Telescope should yield more accurate LFs.

Keywords: luminosity function; tidal disruption; accretion; wide-field telescopes; transient sources; time domain astronomy
Detailed Iron-peak Element Abundances in Three Very Metal-poor Stars

We have obtained new detailed abundances of the Fe-group elements Sc through Zn (Z = 21-30) in three very metal-poor ([Fe/H] ≈ -3) stars: BD+03o740, BD-13o3442, and CD-33o1173. High-resolution ultraviolet Hubble Space Telescope/Space Telescope Imaging Spectrograph spectra in the wavelength range 2300-3050 Å were gathered, and complemented by an assortment of optical echelle spectra. The analysis featured recent laboratory atomic data for a number of neutral and ionized species for all Fe-group elements except Cu and Zn. A detailed examination of scandium, titanium, and vanadium abundances in large-sample spectroscopic surveys indicates that they are positively correlated in stars with [Fe/H] ≤ -2. The abundances of these elements in BD+03o740, BD-13o3442, CD-33o1173, and HD 84937 (studied in a previous paper of this series) are in accord with these trends and lie at the high end of the correlations. Six elements have detectable neutral and ionized features, and generally their abundances are in reasonable agreement. For Cr we find only minimal abundance disagreement between the neutral (mean of [Cr I/Fe] = +0.01) and ionized species (mean of [Cr II/Fe] = +0.08), unlike most studies in the past. The prominent exception is Co, for which the neutral species indicates a significant overabundance (mean of [Co I/H] = -2.53), while no such enhancement is seen for the ionized species (mean of [Co II/H] = -2.93). These new stellar abundances, especially the correlations among Sc, Ti, and V, suggest that models of element production in early high-mass metal-poor stars should be revisited.

Keywords: atomic physics; abundance ratios; galaxy chemical evolution; stellar abundances; stellar nucleosynthesis
Mass Accretion, Spectral, and Photometric Properties of T Tauri Stars in Taurus Based on TESS and LAMOST

We present the analysis of 16 classical T Tauri stars (CTTSs) using LAMOST and TESS data, investigating spectral properties, photometric variations, and mass accretion rates. All 16 stars exhibit emissions in Hα lines, from which the average mass accretion rate of 1.76 × 10‑9 M ⊙ yr‑1 is derived. Two of the stars, DL Tau and Haro 6-13, show mass accretion bursts simultaneously in TESS, ASAS-SN, and/or the ZTF survey. Based on these observations, we find that the mass accretion rates of DL Tau and Haro 6-13 reach their maxima of 2.5 × 10‑8 M ⊙ yr‑1 and 2 × 10‑10 M ⊙ yr‑1, respectively, during the TESS observation. We detect 13 flares among these stars. The flare frequency distribution shows that the CTTSs' flare activity is not only dominated by strong flares with high energy but also much more active than those of solar-type and young low-mass stars. By comparing the variability classes reported in the literature, we find that the transition timescale between different classes of variability in CTTSs, such as from stochastic (S) to bursting (B) or from quasi-periodic symmetric to quasi-periodic dipping, may range from 1.6 to 4 yr. We observe no significant correlation between inclination and mass accretion rates derived from the emission indicators. This suggests that inner disk properties may be more important than those of outer disks. Finally, we find a relatively significant positive correlation between the asymmetric metric M and the cold disk inclination compared to the literature. A weak negative correlation between the periodicity metric Q value and inclination has also been found.

Keywords: star formation; young stellar objects; low mass stars; classical t tauri stars; stellar flares
Universal Relations for the Increase in the Mass and Radius of a Rotating Neutron Star

Rotation causes an increase in a neutron star's mass and equatorial radius. The mass and radius depend sensitively on the unknown equation of state (EOS) of cold, dense matter. However, the increases in mass and radius due to rotation are almost independent of the EOS. The EOS independence leads to the idea of neutron star universality. In this paper, we compute sequences of rotating neutron stars with constant central density. We use a collection of randomly generated EOSs to construct simple correction factors to the mass and radius computed from the equations of hydrostatic equilibrium for nonrotating neutron stars. The correction factors depend only on the nonrotating star's mass and radius and are almost independent of the EOS. This makes it computationally inexpensive to include observations of rotating neutron stars in EOS inference codes. We also construct a mapping from the measured mass and radius of a rotating neutron star to a corresponding nonrotating star. The mapping makes it possible to construct a zero-spin mass-radius curve if the masses and radii of many neutron stars with different spins are measured. We show that the changes in polar and equatorial radii are symmetric, in that the polar radius shrinks at the same rate in which the equatorial radius grows. This symmetry is related to the observation that the equatorial compactness (the ratio of mass to radius) is almost constant on one of the constant-density sequences.

Keywords: neutron stars; millisecond pulsars; rotation powered pulsars; pulsars
Back to the Starting Point: On the Simulation of the Initial Magnetic Fields and Spin Periods of Nonaccreting Pulsars

Neutron stars (NSs) play essential roles in modern astrophysics. The magnetic fields and spin periods of newborn (zero-age) NSs have a large impact on the further evolution of NSs, which are, however, poorly explored in observations due to the difficulty of finding newborn NSs. In this work, we aim to infer the magnetic fields and spin periods (B i and P i) of zero-age NSs from the observed properties of the NS population. We select nonaccreting NSs whose evolution is solely determined by magnetic dipole radiation. We find that both B i and P i can be described by lognormal distribution, and the fitting sensitively depends on our parameters.

Keywords: neutron stars; magnetic fields; accretion; stellar rotation
Hypercubes of AGN Tori (HYPERCAT). I. Models and Image Morphology

Near- and mid-infrared interferometers have resolved the dusty parsec-scale obscurer (torus) around nearby active galactic nuclei (AGNs). With the arrival of extremely large single-aperture telescopes, the emission morphology will soon be resolvable unambiguously, without modeling directly the underlying brightness distribution probed by interferometers today. Simulations must instead deliver the projected 2D brightness distribution as a result of radiative transfer through a 3D distribution of dusty matter around the AGN. We employ such physically motivated 3D dust distributions in tori around AGNs to compute 2D images of the emergent thermal emission, using CLUMPY, a dust radiative transfer code for clumpy media. We demonstrate that CLUMPY models can exhibit morphologies with significant polar elongation in the mid-infrared (i.e., the emission extends perpendicular to the dust distribution) on scales of several parsecs, in line with observations in several nearby AGNs. We characterize the emission and cloud distribution morphologies. The observed emission from near- to mid-infrared wavelengths generally does not trace the bulk of the cloud distribution. The elongation of the emission is sensitive to the torus opening angle or scale height. For cloud distributions with a flat radial profile, polar extended emission is realized only at wavelengths shorter than ~18 μm, and shorter than ~5 μm for steep profiles. We make the full results available through HYPERCAT, a large hypercube of resolved AGN torus brightness maps computed with CLUMPY. HYPERCAT also comprises software to process and analyze such large data cubes and provides tools to simulate observations with various current and future telescopes.

Keywords: computational methods; infrared astronomy; radiative transfer simulations; seyfert galaxies; active galactic nuclei; telescopes
Relativistic Reflection and Reverberation in GX 339-4 with NICER and NuSTAR

We analyze seven Neutron Star Interior Composition Interior Explorer (NICER) and Nuclear Spectroscopic Telescope Array epochs of the black hole X-ray binary GX 339-4 in the hard state during its two most recent hard-only outbursts in 2017 and 2019. These observations cover the 1-100 keV unabsorbed luminosities between 0.3% and 2.1% of the Eddington limit. With NICER's negligible pileup, high count rate, and unprecedented time resolution, we perform a spectral-timing analysis and spectral modeling using relativistic and distant reflection models. Our spectral fitting shows that as the inner disk radius moves inward, the thermal disk emission increases in flux and temperature, the disk becomes more highly ionized, and the reflection fraction increases. This coincides with the inner disk increasing its radiative efficiency around ∼1% Eddington. We see a hint of the hysteresis effect at ∼0.3% of Eddington; the inner radius is significantly truncated during the rise (>49Rg), while only a mild truncation (∼5Rg) is found during the decay. At higher frequencies (2-7 Hz) in the highest-luminosity epoch, a soft lag is present whose energy dependence reveals a thermal reverberation lag with an amplitude similar to previous findings for this source. We also discuss the plausibility of the hysteresis effect and the debate of the disk truncation problem in the hard state.

Keywords: black holes; high energy astrophysics; astrophysical black holes; stellar mass black holes; low-mass x-ray binary stars; x-ray astronomy
The Fast-evolving Type Ib Supernova SN 2015dj in NGC 7371

We present the detailed optical evolution of a Type Ib SN 2015dj in NGC 7371, using data spanning up to ∼170 days after discovery. SN 2015dj shares similarity in light-curve shape with SN 2007gr and peaks at MV = -17.37 ± 0.02 mag. Analytical modeling of the quasi bolometric light curve yields 0.06 ± 0.01 M⊙ of 56Ni, ejecta mass ${M}_{\mathrm{ej}}={1.4}_{-0.5}^{+1.3}$ M⊙, and kinetic energy ${E}_{{\rm{k}}}={0.7}_{-0.3}^{+0.6}\times {10}^{51}$ erg. The spectral features show a fast evolution and resemble those of spherically symmetric ejecta. The analysis of nebular phase spectral lines indicates a progenitor mass between 13-20 M⊙, suggesting a binary scenario.

Keywords: type ib supernovae; core-collapse supernovae
JWST COMPASS: NIRSpec/G395H Transmission Observations of the Super-Earth TOI-836b

We present two transit observations of the ∼870 K, 1.7 R ⊕ super-Earth TOI-836b with JWST NIRSpec/G395H, resulting in a 2.8–5.2 μm transmission spectrum. Using two different reduction pipelines, we obtain a median transit depth precision of 34 ppm for Visit 1 and 36 ppm for Visit 2, leading to a combined precision of 25 ppm in spectroscopic channels 30 pixels wide (∼0.02 μm). We find that the transmission spectrum from both visits is well fit by a zero-sloped line, by fitting zero-sloped and sloped lines as well as step functions to our data. Combining both visits, we are able to rule out atmospheres with metallicities <250 times solar for an opaque pressure level of 0.1 bar, corresponding to mean molecular weights of ≲6 g mol‑1. We therefore conclude that TOI-836b does not have an H2-dominated atmosphere, in possible contrast with its larger, exterior sibling planet, TOI-836 c. We recommend that future proposals to observe small planets exercise caution when requiring specific numbers of transits to rule out physical scenarios, particularly for high metallicities and planets around bright host stars, as PandExo predictions appear to be more optimistic than what the gains from additional transits implied by our data suggest.

Keywords: exoplanet atmospheric composition; exoplanet atmospheres; exoplanets; infrared spectroscopy
Slowly Cooling White Dwarfs in NGC 6752

Recently, a new class of white dwarfs ("slowly cooling WDs") has been identified in the globular cluster M13. The cooling time of these stars is increased by stable thermonuclear hydrogen burning in their residual envelope. These WDs are thought to be originated by horizontal branch (HB) stars populating the HB blue tail that skipped the asymptotic giant branch phase. To further explore this phenomenon, we took advantage of deep photometric data acquired with the Hubble Space Telescope in the near-ultraviolet and investigate the bright portion of the WD cooling sequence in NGC 6752, another Galactic globular cluster with a metallicity, age, and HB morphology similar to M13. The normalized WD luminosity function derived in NGC 6752 turns out to be impressively similar to that observed in M13, in agreement with the fact that the stellar mass distribution along the HB of these two systems is almost identical. As in the case of M13, the comparison with theoretical predictions is consistent with ~70% of the investigated WDs evolving at slower rates than standard, purely cooling WDs. Thanks to its relatively short distance from Earth, NGC 6752 photometry reaches a luminosity 1 order of a magnitude fainter than the case of M13, allowing us to sample a regime where the cooling time delay, with respect to standard WD models, reaches ~300 Myr. The results presented in this paper provide new evidence for the existence of slowly cooling WDs and further support to the scenario proposing a direct causal connection between this phenomenon and the HB morphology of the host stellar cluster.

Keywords: globular star clusters; hertzsprung russell diagram; white dwarf stars; ultraviolet photometry
The Impact of Binaries on the Dynamical Mass Estimate of Dwarf Galaxies

Binary stars are recognized to be important in driving the dynamical evolution of stellar systems and also in determining some of their observational features. In this study, we explore the role that binary stars have in modulating the estimates of the velocity dispersion of stellar systems. To this aim, we developed a tool that allows investigation of the dependence of synthetic velocity dispersion on a number of crucial quantities characterizing the binary content: binary fraction and the distributions of their mass ratio, eccentricity, and semimajor axis. As an application, we evaluate the impact that binary stars have on the estimation of the dynamical mass of dwarf spheroidal and ultrafaint dwarf galaxies, finding that it can be particularly relevant, especially for low-mass and low-density systems. These results bear profound implications for the interpretation of the measured velocity dispersion in such systems, since it weakens or relieves the claim for the need of large amounts of dark matter.

Keywords: binary stars; dwarf galaxies; dark matter