adsabs/SciX_UAT_keywords huggingface dataset:
A Search for Cloud Cores Affected by Shocked Carbon Chain Chemistry in L1251

We searched for shocked carbon chain chemistry (SCCC) sources with C3S abundances surpassing those of HC5N toward the dark cloud L1251, using the Effelsberg telescope at the K band (18-26 GHz). L1251-1 and L1251-3 are identified as the most promising SCCC sources. The two sources harbor young stellar objects. We conducted mapping observations toward L1251-A, the western tail of L1251, at λ ∼ 3 mm with the Purple Mountain Observatory 13.7 m and the Nobeyama Radio Observatory 45 m telescopes in lines of C2H, N2H+, CS, HCO+, SO, HC3N, and C18O as well as in CO 3-2 using the James Clerk Maxwell Telescope (JCMT). The spectral data were combined with archival data including Spitzer and Herschel continuum maps for further analysis. Filamentary substructures labeled as F1-F6 were extracted in L1251, with F1 being associated with L1251-A hosting L1251-1. The peak positions of dense gas traced by HCO+ are misaligned relative to those of the dust clumps. Episodic outflows are common in this region. The twisted morphology of F1 and velocity distribution along L1251-A may originate from stellar feedback. SCCC in L1251-1 may have been caused by outflow activities originated from the infrared source IRS1. The signposts of ongoing SCCC and the broadened line widths of C3S and C4H in L1251-1 as well as the distribution of HC3N are also related to outflow activities in this region. L1251-1 (IRS1) together with the previously identified SCCC source IRS3 demonstrate that L1251-A is an excellent region to study SCCC.

Keywords: chemical abundances; astrochemistry; molecular clouds; infrared dark clouds; stellar jets; stellar-interstellar interactions
Absorption-line Abundances in the SMC-like Galaxy UGC 5282: Evidence of ISM Dilution from Inflows on Kiloparsec Scales

We present a Hubble Space Telescope Cosmic Origins Spectrograph spectrum of the QSO SDSS J095109.12+330745.8 ( ${z}_{\mathrm{em}}=0.645$ ) whose sightline passes through the SMC-like dwarf galaxy UGC 5282 ( ${M}_{B}=-16.0$ , cz = 1577 km s-1), 1.2 kpc in projection from the central H II region of the galaxy. Damped Lyα (DLA) absorption is detected at the redshift of UGC 5282 with log [N(H I) cm ${}^{-2}]={20.89}_{-0.21}^{+0.12}$ . Analysis of the accompanying S II, P II, and O I metal lines yields a neutral gas metallicity, ${Z}_{{\rm{H}}{\rm{I}}}$ , of [S/H] ≃ [P/H] = -0.80 ± 0.24. The metallicity of ionized gas from the central H II region ${Z}_{{\rm{H}}{\rm{II}}}$ measured from its emission lines is [O/H] = -0.37 ± 0.10, a difference of +0.43 ± 0.26 from ${Z}_{{\rm{H}}{\rm{I}}}$ . This difference δ is consistent with that seen toward H II regions in other star-forming galaxies and supports the idea that ionized gas near star-forming regions shows systematically higher metallicities than exist in the rest of a galaxy's neutral interstellar medium (ISM). The positive values of δ found in UGC 5282 (and the other star-forming galaxies) is likely due to infalling low-metallicity gas from the intergalactic medium that mixes with the galaxy's ISM on kiloparsec scales. This model is also consistent with broad Lyα emission detected at the bottom of the DLA absorption, offset by ∼125 km s-1 from the absorption velocity. Models of galaxy evolution that attempt to replicate population characteristics, such as the mass-metallicity relation, may need to start with a galaxy metallicity represented by ${Z}_{{\rm{H}}{\rm{I}}}$ rather than that measured traditionally from ${Z}_{{\rm{H}}{\rm{II}}}$ .

Keywords: quasar absorption line spectroscopy; interstellar line absorption; dwarf irregular galaxies; metallicity; damped lyman-alpha systems; small magellanic cloud
The Behavior of the Bp Stars in the Far UV-Paper VII: HD 22316

The analysis of seven spectra of the B9 Cr Hg Si star HD 22316 recorded by the SWP camera on board the International Ultraviolet Explorer does not reveal any variations of the far ultraviolet spectral energy distribution shortwards of 1800 Å in spectra collected over 2 yr with identical exposure times. The low excitation line at 1363.45 Å and the resonance line of Cl I at 1379.53 Å are most likely present. Several lines of Al II, Si II, P II but none of S I could be found at their expected wavelengths. The synthesis of several Al II lines consistently yields a clear underabundance of aluminum of about 0.40 times the solar aluminum abundance.

Keywords: chemically peculiar stars; bp stars
The Fifth Candidate for an Intermediate-mass Black Hole in the Galactic Center

We report the results of high-resolution molecular line observations of the high-velocity compact cloud HCN-0.085-0.094 with the Atacama Large Millimeter/submillimeter Array. The HCN J = 4-3, HCO+ J = 4-3, and CS J = 7-6 line images reveal that HCN-0.085-0.094 consists mainly of three small clumps with extremely broad velocity widths. Each of the three clumps has a 5.5 GHz radio continuum counterpart in its periphery toward Sgr A*. The positional relationship indicates that their surfaces have been ionized by ultraviolet photons from young stars in the central cluster, suggesting the clumps are in close proximity to the Galactic nucleus. One of the three clumps has a ring-like structure with a very steep velocity gradient. This kinematical structure suggests an orbit around a point-like object with a mass of ∼104 M⊙. The absence of stellar counterparts indicates that the point-like object may be a quiescent black hole. This discovery adds another intermediate-mass black hole candidate in the central region of our Galaxy.

Keywords: galactic center; molecular clouds; intermediate-mass black holes; submillimeter astronomy
Intermediate-mass Black Holes' Effects on Compact Object Binaries

Although their existence is not yet confirmed observationally, intermediate-mass black holes (IMBHs) may play a key role in the dynamics of galactic nuclei. In this paper, we neglect the effect of the nuclear star cluster itself and investigate only how a small reservoir of IMBHs influences the secular dynamics of stellar-mass black hole binaries, using N-body simulations. We show that our simplifications are valid and that the IMBHs significantly enhance binary evaporation by pushing the binaries into the Hill-unstable region of parameter space, where they are separated by the supermassive black hole's tidal field. For binaries in the S-cluster region of the Milky Way, IMBHs drive the binaries to merge in up to 1%-6% of cases, assuming five IMBHs within 5 pc of mass 104 M⊙ each. Observations of binaries in the Galactic center may strongly constrain the population of IMBHs therein.

Keywords: galactic center; intermediate-mass black holes
Evidence for Disk Truncation at Low Accretion States of the Black Hole Binary MAXI J1820+070 Observed by NuSTAR and XMM-Newton

We present results from NuSTAR and XMM-Newton observations of the new black hole X-ray binary MAXI J1820+070 at low accretion rates (below 1% of the Eddington luminosity). We detect a narrow Fe Kα emission line, in contrast to the broad and asymmetric Fe Kα line profiles commonly present in black hole binaries at high accretion rates. The narrow line, with weak relativistic broadening, indicates that the Fe Kα line is produced at a large disk radius. Fitting with disk reflection models assuming standard disk emissivity finds a large disk truncation radius (a few tens to a few hundreds of gravitational radii, depending on the disk inclination). In addition, we detect a quasi-periodic oscillation (QPO) varying in frequency between 11.6 ± 0.2 mHz and 2.8 ± 0.1 mHz. The very low QPO frequencies suggest a large size for the optically thin Comptonization region according to the Lense-Thirring precession model, supporting that the accretion disk recedes from the innermost stable circular orbit and is replaced by advection-dominated accretion flow at low accretion rates. We also discuss the possibility of an alternative accretion geometry that the narrow Fe Kα line is produced by a lamppost corona with a large height illuminating the disk.

Keywords: accretion; black hole physics; x-ray transient sources; x-ray binary stars
Sudden Dimming of the Symbiotic Mira HM Sge

The Symbiotic Mira HM Sge has dimmed considerably over the last year, beyond what is expected of its pulsation-related variability. HM Sge is composed of a cool oxygen-rich AGB star accreting onto a hotter white dwarf companion. The system brightened 6 mag in the optical in 1975 as a result of a Nova-like outburst. It has since dimmed and plateaued in the visible, while gradually growing in brightness in the near-IR over the past 15 yr (0.092 mag yr-1). Within the last year, however, the brightness has dropped by 1.52 mag in the I-band. While the system is expected to be near its pulsation minimum, the brightness is below the values expected of the last three pulsation cycles, and appears independent of the system's fundamental mode pulsations. We suspect this may be the result of a change in the orientation of the system or episodic mass loss.

Keywords: symbiotic binary stars; asymptotic giant branch; mira variable stars; stellar mass loss; symbiotic novae
The Initial Mass Function and Other Stellar Properties Across the Core of the Hydra I Cluster

The Hydra I cluster offers an excellent opportunity to study and compare the relic old stellar populations in the core of its two brightest galaxies. In addition, the differing kinematics of the two galaxies allows a test of the local validity of general scaling relations. In this work, we present a direct comparison employing full spectral fitting of new high-quality long-slit optical and near-infrared spectroscopic data. We retrieve age, metallicity, and 19 elemental abundances out to ~12 kpc within each galaxy, as well as the Initial Mass Function (IMF) in their central regions. Our results suggest that the inner ~5 kpc regions of both galaxies, despite their different masses, formed at the same time and evolved with a similar star formation timescale and chemical enrichment, confirming their early formation in the cluster buildup. Only the overall metallicity and IMF radial profiles show differences connected with their different velocity dispersion profiles. The radial trends of the IMF positively correlate with both [Z/H] and σ. While the trends of the IMF slope values with metallicity agree with a global trend for both galaxies, the trends with the velocity dispersion exhibit differences. The outer regions show signs of mixed stellar populations with large differences in chemical content compared to the centers, but with similarly old ages. * This paper includes data gathered with the 6.5 m Magellan Telescopes located at Las Campanas Observatory, Chile.

Keywords: early-type galaxies; initial mass function
Identifying Exoplanet Candidates Using WaveCeptionNet

In this study, we propose a wavelet-transform-based light curve representation method and a CNN model based on Inception-v3 for fast classification of light curves, enabling the quick discovery of potentially interesting targets from massive data. Experimental results on real observation data from the TESS showed that our wavelet processing method achieved about a 32-fold dimension reduction, while largely removing noise. We fed the wavelet-decomposed components of light curves into our improved Inception-v3 CNN model, achieving an accuracy of about 95%. Furthermore, our model achieves F1-scores of 95.63%, 95.93%, 95.65%, and 89.60% for eclipsing binaries, planet candidates, variable stars, and instrument noise, respectively. The precision rate of planet candidates identification reaches 96.49%, and the recall rate reaches 95.38% in the test set. The results demonstrate the effectiveness of our method for light curve.

Keywords: exoplanet astronomy; exoplanet detection methods
Efficiency of Electromagnetic Emission by Electrostatic Turbulence in Solar Wind and Coronal Plasmas with Density Inhomogeneities

We present a new method to semianalytically calculate the radiation efficiency of electromagnetic waves emitted at specific frequencies by electrostatic wave turbulence in solar wind and coronal plasmas with random density fluctuations. This method is applied to the case of electromagnetic emission radiated at the fundamental plasma frequency ωp by beam-driven Langmuir wave turbulence during Type III solar bursts. It is supposed that the main radiation mechanism is the linear conversion of electrostatic to electromagnetic waves on the background plasma density fluctuations, at constant frequency. The radiation efficiency (emissivity) of such a process is larger than that obtained in the framework of models where the low frequency density fluctuations and the corresponding ion sound waves are not external but produced by the electrostatic wave turbulence itself through nonlinear wave-wave interactions. Results show that the radiation efficiency of Langmuir wave turbulence into electromagnetic emissions at ωp is nearly constant asymptotically, with the electromagnetic energy density growing linearly with time, and is proportional to the average level of density fluctuations. Comparisons with another analytical method developed by the authors and with space observations are satisfactory.

Keywords: radio bursts; solar flares; solar physics; plasma physics; solar wind; solar corona; space plasmas; solar radio emission; plasma astrophysics; heliosphere; radio sources
Simultaneous Estimates of Star-cluster Age, Metallicity, Mass, and Extinction (SESAMME). I. Presenting an MCMC Approach to Spectral Stellar Population Fitting

We present the first version release of SESAMME, a public, Python-based full spectrum fitting tool for Simultaneous Estimates of Star-cluster Age, Metallicity, Mass, and Extinction. SESAMME compares an input spectrum of a star cluster to a grid of stellar population models with an added nebular continuum component, using Markov Chain Monte Carlo methods to sample the posterior probability distribution in four dimensions: cluster age, stellar metallicity Z, reddening E(B - V), and a normalization parameter equivalent to a cluster mass. SESAMME is highly flexible in the stellar population models that it can use to model a spectrum; our testing and initial science applications use both BPASS and Starburst99. We illustrate the ability of SESAMME to recover accurate ages and metallicities even at a moderate signal-to-noise ratio (S/N ~ 3-5 per wavelength bin) using synthetic, noise-added model spectra of young star clusters. Finally, we test the consistency of SESAMME with other age and metallicity estimates from the literature using a sample of Hubble Space Telescope/Cosmic Origins Spectrograph far-UV spectra toward young, massive clusters in M83 and NGC 1313. We find that, on the whole, SESAMME infers star cluster properties that are consistent with the literature in both low- and high-metallicity environments.

Keywords: star clusters; astronomy software; ultraviolet spectroscopy
First Insights into the Applicability and Importance of Different 3D Magnetic Field Extrapolation Approaches for Studying the Preeruptive Conditions of Solar Active Regions

The three-dimensional (3D) coronal magnetic field has not yet been directly observed. However, for a better understanding and prediction of magnetically driven solar eruptions, 3D models of solar active regions are required. This work aims to provide insight into the significance of different extrapolation models for analyzing the preeruptive conditions of active regions with morphological parameters in 3D. Here, we employed potential field (PF), linear force-free field (LFFF), and nonlinear force-free field (NLFFF) models and a neural network-based method integrating observational data and NLFFF physics (NF2). The 3D coronal magnetic field structure of a "flaring" (AR11166) and "flare-quiet" (AR12645) active region, in terms of their flare productivity, is constructed via the four extrapolation methods. To analyze the evolution of the field, six prediction parameters were employed throughout, from the photosphere up to the base of the lower corona. First, we find that the evolution of the adopted morphological parameters exhibits similarity across the investigated time period when considering the four types of extrapolations. Second, all the parameters exhibited preeruptive conditions not only at the photosphere but also at higher altitudes in the case of active region (AR) 11166, while three out of the six proxies also exhibited preeruptive conditions in the case of AR12645. We conclude that: (i) the combined application of several different precursor parameters is important in the lower solar atmosphere to improve eruption predictions, and (ii) to gain a quick yet reliable insight into the preflare evolution of active regions in 3D, the PF and LFFF are acceptable; however, the NF2 method is likely the more suitable option.

Keywords: solar flares; solar active region magnetic fields; solar active regions
Changes in a Dusty Ringlet in the Cassini Division after 2010

A dusty ringlet designated R/2006 S3, also known as the "Charming Ringlet," is located around 119,940 km from the center of Saturn within the Laplace Gap in the Cassini Division. Prior to 2010, the ringlet had a simple radial profile and a predictable eccentric shape with two components, one forced by solar radiation pressure and the other freely precessing around the planet. However, observations made by the Cassini spacecraft since late 2012 revealed a shelf of material extending inwards from the ringlet that was not present in the earlier observations. Closer inspection of images obtained after 2012 shows that sometime between 2010 and 2012, the freely precessing component of the ringlet's eccentricity increased by over 50%, and that for at least 3 yr after 2012, the ringlet had longitudinal brightness variations that rotated around the planet at a range of rates corresponding to ∼60 km in orbital semimajor axis. Some event therefore disturbed this ringlet between 2010 and late 2012.

Keywords: saturn; planetary rings; solar system; interplanetary dust; orbits; celestial mechanics
The Morpho-kinematic Architecture of Super Star Clusters in the Center of NGC 253

The center of the nearby galaxy NGC 253 hosts a population of more than a dozen super star clusters (SSCs) that are still in the process of forming. The majority of the star formation of the burst is concentrated in these SSCs, and the starburst is powering a multiphase outflow from the galaxy. In this work, we measure the 350 GHz dust continuum emission toward the center of NGC 253 at 47 mas (0.8 pc) resolution using data from the Atacama Large Millimeter/submillimeter Array. We report the detection of 350 GHz (dust) continuum emission in the outflow for the first time, associated with the prominent South-West streamer. In this feature, the dust emission has a width of ≈8 pc, is located at the outer edge of the CO emission, and corresponds to a molecular gas mass of ~(8-17)×106 M ⊙. In the starburst nucleus, we measure the resolved radial profiles, sizes, and molecular gas masses of the SSCs. Compared to previous work at the somewhat lower spatial resolution, the SSCs here break apart into smaller substructures with radii 0.4-0.7 pc. In projection, the SSCs, dust, and dense molecular gas appear to be arranged as a thin, almost linear, structure roughly 155 pc in length. The morphology and kinematics of this structure can be well explained as gas following x 2 orbits at the center of a barred potential. We constrain the morpho-kinematic arrangement of the SSCs themselves, finding that an elliptical, angular-momentum-conserving ring is a good description of both the morphology and kinematics of the SSCs.

Keywords: starburst galaxies; young star clusters; interstellar medium; barred spiral galaxies; galactic winds; galaxy nuclei; molecular gas; interstellar dynamics
On the Diversity of Mixing and Helium Core Masses of B-type Dwarfs from Gravity-mode Asteroseismology

The chemical evolution of the galaxy is largely guided by the yields from massive stars. Their evolution is heavily influenced by their internal mixing, allowing the stars to live longer and yield a more massive helium core at the end of their main-sequence evolution. Asteroseismology is a powerful tool for studying stellar interiors by providing direct probes of the interior physics of the oscillating stars. This work revisits the recently derived internal mixing profiles of 26 slowly pulsating B stars observed by the Kepler space telescope, in order to investigate how well the mixing profiles can in fact be distinguished from one another as well as provide predictions for the expected helium core masses obtained at the end of the main-sequence evolution. We find that for five of these stars the mixing profile is derived unambiguously, while the remaining stars have at least one other mixing profile which explains the oscillations equally well. Convective penetration is preferred over exponential diffusive overshoot for ≈55% of the stars, while stratified mixing is preferred in the envelope (≈39%). We estimate the expected helium core masses obtained at the end of the main-sequence evolution and find them to be highly influenced by the estimated amount of mixing occurring in the envelopes of the stars.

Keywords: stellar cores; stellar interiors; stellar pulsations; stellar evolution; stellar diffusion
A Hale-like Cycle in the Solar Twin 18 Scorpii

Characterizing the cyclic magnetic activity of stars that are close approximations of our Sun offers our best hope for understanding our Sun's current and past magnetism, the space weather around solar-type stars, and more generally, the dynamos of other cool stars. The nearest current approximation to the Sun is the solar twin 18 Scorpii, a naked-eye Sun-like star of spectral type G2 Va. However, while 18 Scorpii's physical parameters closely match those of the Sun, its activity cycle is about 7 yr, and shorter than the solar cycle. We report the measurement of a periodicity of 15 yr that corresponds to a longer activity cycle for 18 Scorpii based on observations extending to the last three decades. The global magnetic geometry of 18 Scorpii changes with this 15 yr cycle and appears to be equivalent to the solar 22 yr magnetic polarity cycle. These results suggest that 18 Scorpii is also a magnetic proxy for a younger Sun, adding an important new datum for testing dynamo theory and magnetic evolution of low-mass stars. The results perturb our understanding of the relationship between cycle and rotation, constrain the Sun's magnetism and the Sun-Earth connection over the past billion years, and suggest that solar Schwabe and Hale cycle periods have increased over that time span.

Keywords: solar cycle; stellar evolution; stellar magnetic fields; solar analogs; spectropolarimetry
A Possible Optical Quasiperiodic Oscillation of 134 days in the Radio-loud Narrow-line Seyfert 1 Galaxy TXS 1206+549 at z = 1.34

Here we report an optical quasiperiodic oscillation (QPO) with a period of ~134 days detected in g- and r-band light curves of the narrow-line Seyfert 1 galaxy TXS 1206+549 at a redshift of 1.34 with data from observations at the Zwicky Transient Facility (ZTF). After considering the trial factor, the significance levels in the two bands are 3.1σ and 2.6σ, respectively. The QPO signal presents about 10 cycles ranging from 2018 March to 2021 December, thus lasting ~4 yr. A nearly sinusoidal profile also appears in the folded light curves by using a phase-resolved analysis. Interestingly, in the simultaneous light curve with the timescale of ZTF observations, a potential periodic signal with a similar period is detected in the o-band light curve from Asteroid Terrestrial-impact Last Alert System data; additionally, a weak peak is also detected at a similar period in the γ-ray light curve obtained from Fermi Gamma-ray Space Telescope data. Some potential origins of periodicities in active galactic nuclei are discussed for the QPO reported here.

Keywords: active galactic nuclei; time series analysis; period search