adsabs/SciX_UAT_keywords huggingface dataset:
Boundary Treatment for the Subsonic/Alfvénic Inner Boundary at 2.5 R ⊙ in a Time-dependent 3D Magnetohydrodynamics Solar Wind Simulation Model

A new magnetohydrodynamics (MHD) simulation model of the global solar corona and solar wind is presented. The model covers the range of heliocentric distance from 2.5 solar radii, so that coronal mass ejections at the earliest phase near the Sun can be treated in the future. This model is constructed by introducing a characteristics-based boundary treatment to an existing heliosphere 3D MHD model. In tailoring a set of characteristic equations for this new model, we assume that the coronal magnetic field is open to interplanetary space and that the solar coronal plasma is flowing outward everywhere at 2.5 solar radii. The characteristic equations for the subsonic/Alfvénic inner boundary surface are satisfied by altering the plasma density and/or temperature to maintain a polytropic relationship. In this article, the details of the characteristics-based boundary treatment for the middle of the corona (named CharM) are provided. The quasi-steady states of the solar wind derived from simulations with various choices of a parameter in the boundary treatments are compared and examined. Although further improvements are needed, we apply the new boundary treatment to simulations for three Carrington rotation periods from the minimum to maximum phase of the solar activity cycle, and show that an optimal choice yields a reasonable quasi-steady state of the transonic/Alfvénic solar wind matching the specified subsonic/Alfvénic plasma speed at 2.5 R ⊙.

Keywords: solar wind; solar corona; magnetohydrodynamical simulations
Compact Symmetric Objects. I. Toward a Comprehensive Bona Fide Catalog

Compact symmetric objects (CSOs) are jetted active galactic nuclei (AGN) with overall projected size <1 kpc. The classification was introduced to distinguish these objects from the majority of compact jetted AGN in centimeter-wavelength very long baseline interferometry observations, where the observed emission is relativistically boosted toward the observer. The original classification criteria for CSOs were (i) evidence of emission on both sides of the center of activity and (ii) overall size <1 kpc. However, some relativistically boosted objects with jet axes close to the line of sight appear symmetric and have been misclassified as CSOs, thereby undermining the CSO classification. This is because two essential CSO properties, pointed out in the original papers, have been neglected: (iii) low variability and (iv) low apparent speeds along the jets. As a first step toward creating a comprehensive catalog of "bona fide" CSOs, we identify 79 bona fide CSOs, including 15 objects claimed as confirmed CSOs here for the first time, that match the CSO selection criteria. This sample of bona fide CSOs can be used for astrophysical studies of CSOs without contamination by misclassified CSOs. We show that the fraction of CSOs in complete flux density limited AGN samples with S 5GHz > 700 mJy is between (6.8 ± 1.6)% and (8.5 ± 1.8)%.

Keywords: active galactic nuclei; relativistic jets; active galaxies
Stellar Populations of a Sample of Optically Selected AGN-host Dwarf Galaxies

In this paper we present our studies on the stellar populations and star formation histories (SFHs) for the Reines et al. sample of 136 dwarf galaxies that host active galactic nuclei (AGNs), selected from the Sloan Digital Sky Survey Data Release 8. We derive stellar populations and reconstruct SFHs for these AGN-host dwarfs using the stellar population synthesis code STARLIGHT. Our results suggest that these AGN-host dwarfs have assembled their stellar masses within a narrow period of time with the stellar mass-weighted ages in the range of 109-1010 yr, but show a wide diversity of SFHs with the luminosity-weighted stellar ages in the range of 107-1010 yr. The old population (t > 109 yr) contributes most to the galaxy light for the majority of the sample; the young population (t < 108 yr) also appears in significant but widely varying fractions, while the intermediate-age population (108 < t < 109 yr) in general contributes less to the optical continuum at 4020 Å. We also find that these dwarfs follow a similar mass-metallicity relation to normal star-forming galaxies, indicating that AGNs have little effect on the chemical evolution of the host galaxy. We further investigate the relation between the derived SFHs and morphology of the host galaxy, and find no correlation. Comparing the SFHs with the luminosity of the [O III] λ5007 line ( ${L}_{[{\rm{O}}{\rm\small{III}}]}$ ), we find a mild correlation exists when ${L}_{[{\rm{O}}{\rm\small{III}}]}\gt {10}^{39}$ erg s-1, indicating a physical connection between star formation and AGN activities in these dwarf galaxies.

Keywords: galaxies; dwarf galaxies; active galaxies; galaxy stellar content
Broadband X-Ray Spectroscopy and Estimation of Spin of the Galactic Black Hole Candidate GRS 1758-258

We present the results of a broadband (0.5-78 keV) X-ray spectral study of the persistent Galactic black hole X-ray binary GRS 1758-258 observed simultaneously by Swift and NuSTAR. Fitting with an absorbed power-law model revealed a broad Fe line and reflection hump in the spectrum. We used different flavors of the relativistic reflection model for the spectral analysis. All models indicate the spin of the black hole in GRS 1758-258 is >0.92. The source was in the low hard state during the observation, with the hot electron temperature of the corona estimated to be kT e ~ 140 keV. The black hole is found to be accreting at ~1.5% of the Eddington limit during the observation, assuming the black hole mass of 10 M ⊙ and distance of 8 kpc.

Keywords: astrophysical black holes; accretion; low-mass x-ray binary stars; black hole physics; high energy astrophysics
The 2022 Outburst of IGR J17091–3624: Connecting the Exotic GRS 1915+105 to Standard Black Hole X-Ray Binaries

While the standard X-ray variability of black hole X-ray binaries (BHXBs) is stochastic and noisy, there are two known BHXBs that exhibit exotic "heartbeat"-like variability in their lightcurves: GRS 1915+105 and IGR J17091–3624. In 2022, IGR J17091–3624 went into outburst for the first time in the NICER/NuSTAR era. These exquisite data allow us to simultaneously track the exotic variability and the corresponding spectral features with unprecedented detail. We find that as in typical BHXBs, the outburst began in the hard state, then continued in the intermediate state, but then transitioned to an exotic soft state, where we identify two types of heartbeat-like variability (Class V and a new Class X). The flux energy spectra show a broad iron emission line due to relativistic reflection when there is no exotic variability, and absorption features from highly ionized iron when the source exhibits exotic variability. Whether absorption lines from highly ionized iron are detected in IGR J17091–3624 is not determined by the spectral state alone, but rather is determined by the presence of exotic variability; in a soft spectral state, absorption lines are only detected along with exotic variability. Our finding indicates that IGR J17091–3624 can be seen as a bridge between the most peculiar BHXB GRS 1915+105 and "normal" BHXBs, because it alternates between the conventional and exotic behaviors of BHXBs. We discuss the physical nature of the absorbing material and exotic variability in light of this new legacy data set.

Keywords: black hole physics; black holes; low-mass x-ray binary stars
Gaia22eor: Symbiotic Star V2756 Sgr Detected in a Deep Eclipse

V2756 Sgr is a long-known S-type symbiotic binary that was recently detected in ~1 mag eclipse-like fading by the Gaia satellite. This behavior was reported as a Gaia Science Alert under the designation Gaia22eor. V2756 Sgr has not been reported as an eclipsing symbiotic system. In this contribution, we have investigated the recent light curves of this target obtained by Gaia and ASAS-SN survey and supplemented these data by the photometry from the ASAS survey and DASCH archive. In addition, low-resolution BP/RP spectra from Gaia were examined. Based on the presented analysis, we conclude that the observed fading is indeed an eclipse of the hot component of V2756 Sgr by the cool giant. The data also allowed us to refine the orbital period to 725 ± 3 days.

Keywords: symbiotic binary stars; eclipsing binary stars; photometry; gaia
A Survey for C II Emission-line Stars in the Large Magellanic Cloud. II. Final Results and the Origin of C II Emission in [WC] Spectra

We present the final results of an imaging and spectroscopic search for stars in the Large Magellanic Cloud (LMC) with C II λλ7231, 7236 emission lines. The goal is to identify and study [WC11] stars, the coolest of the low-mass Wolf-Rayet sequence, and a subset of central stars of planetary nebulae where the C II lines are known to be especially prominent. A recent serendipitous discovery of an LMC [WC11] raised the possibility that these objects, although difficult to identify, might in fact be more common than previously believed. Several new members of this rare class have been found in this survey. It now seems clear, however, that a significant number of these stars are not hiding among the general [WC] population. We point out that the C II doublet intensity ratio observed in our spectra proves to neatly divide the objects into two distinct groups, with the C II emission likely originating from either the stellar wind or a surrounding nebula. The physics of the C II emission mechanism correctly explains this bifurcation. Spectral subtypes are suggested for most of the objects. The numerous spectroscopic clues now available for these objects should facilitate future detailed modeling.

Keywords: planetary nebulae nuclei; wolf-rayet stars
Modeling the Sgr A* Black Hole Immersed in a Dark Matter Spike

In this paper, we investigate the effects of a dark matter (DM) spike on the neighborhood of Sgr A*, the black hole (BH) in the center of the Milky Way. Our main goal is to investigate whether current and future astronomical observations of Sgr A* could detect the presence of such a DM spike. At first, we construct the spacetime metric around a static and spherically symmetric BH with a DM spike, and later, this solution is generalized for a rotating BH using the Newman-Janis-Azreg-Aïnou algorithm. For the static BH metric, we use the data of the S2 star orbiting Sgr A* to determine and analyze the constraints on the two free parameters characterizing the density and innermost boundary of the DM halo surrounding the BH. Furthermore, by making use of the available observational data for the DM spike density ρsp and the DM spike radius Rsp in the Milky Way, we consider a geometrically thick accretion disk model around the Sgr A* BH and demonstrate that the effect of DM distribution on the shadow radius and the image of the BH is considerably weak for realistic DM densities, becoming significant only when the DM density is of the order ρsp ~ (10-19-10-20) g cm-3 near the BH. We further analyze the possibility of observing this effect with radio interferometry, simulating observations with an EHT-like array, and find that it is unlikely to be detectable in the near future.

Keywords: dark matter density; milky way dark matter halo; supermassive black holes; accretion
Feedback in Forming Star Clusters: The Mass-Radius Relation and Mass Function of Molecular Clumps in the Large Magellanic Cloud

We derive the mass-radius relation and mass function of molecular clumps in the Large Magellanic Cloud (LMC) and interpret them in terms of the simple feedback model proposed by Fall et al. (FKM). Our work utilizes the dendrogram-based catalog of clumps compiled by Wong et al. from 12CO and 13CO maps of six giant molecular clouds in the LMC observed with the Atacama Large Millimeter Array. The Magellanic Clouds are the only external galaxies for which this type of analysis is possible at the necessary spatial resolution (∼1 pc). We find that the mass-radius relation and mass function of LMC clumps have power-law forms, R ∝ Mα and ${dN}/{dM}\propto {M}^{\beta }$ <!-- --> , with indices α = 0.36 ± 0.03 and β = -1.8 ± 0.1 over the mass ranges 102M⊙ ≲ M ≲ 105M⊙ and 102M⊙ ≲M ≲ 104M⊙, respectively. With these values of α and β for the clumps (i.e., protoclusters), the predicted index for the mass function of young LMC clusters from the FKM model is β ≈ 1.7, in good agreement with the observed index. The situation portrayed here for clumps and clusters in the LMC replicates that in the Milky Way.

Keywords: interstellar medium
On the Long-term Weathering of Airless Body Surfaces by the Heavy Minor Ions of the Solar Wind: Inputs from Ion Observations and SRIM Simulations

The importance of solar wind minor ions heavier than alpha particles in weathering airless body surfaces is an open debate. The fundamental question at stake is whether the variety of different minor ion species, their high masses, and their high charge states may overcome their low densities in the solar wind to enable them to significantly contribute to ion weathering processes. Here, long-term effects that develop on geological timescales are investigated. To do so, the long-term averaged energy spectrum of thermal and suprathermal solar wind ions is estimated by compiling and contrasting ion measurements gathered by the Advanced Composition Explorer (ACE), Wind, Solar TErrestrial RElations Observatory (STEREO), ARTEMIS, and Mars Atmosphere and Volatile Evolution (MAVEN) missions. The long-term ion environment is then convolved with Stopping and Range of Ions in Matter simulations. Combining these data and models, we find that solar wind minor ions significantly alter airless body surfaces, as they contribute to 8%-14% of the total sputtering and create 20%-50% of atomic displacements at depths greater than 100 nm. The new approach presented in this article therefore confirms that solar wind minor ions play an important role in the ion weathering of airless surfaces throughout the solar system.

Keywords: solar wind; lunar composition; the moon; dwarf planets; planetary surfaces; lunar surface; surface processes
The Chemical Nature of Orion Protostars: Are ORANGES Different from PEACHES? ORANGES II.

Understanding the chemical past of our Sun and how life appeared on Earth is no mean feat. The best strategy we can adopt is to study newborn stars located in an environment similar to the one in which our Sun was born and assess their chemical content. In particular, hot corinos are prime targets because recent studies have shown correlations between interstellar complex organic molecules abundances from hot corinos and comets. The ORion ALMA New GEneration Survey aims to assess the number of hot corinos in the closest and best analog to our Sun's birth environment, the OMC-2/3 filament. In this context, we investigated the chemical nature of 19 solar-mass protostars and found that 26% of our sample sources show warm methanol emission indicative of hot corinos. Compared to the Perseus low-mass star-forming region, where the PErseus ALMA CHEmistry Survey detected hot corinos in ~60% of the sources, the hot corinos seem to be relatively scarce in the OMC-2/3 filament. While this suggests that the chemical nature of protostars in Orion and Perseus is different, improved statistics is needed in order to consolidate this result. If the two regions are truly different, this would indicate that the environment is likely playing a role in shaping the chemical composition of protostars.

Keywords: astrochemistry; protostars; star formation; chemical abundances
Statistical Plasma Properties of the Planar and Nonplanar ICME Magnetic Clouds during Solar Cycles 23 and 24

Various remote and in situ observations, along with several models, simulations, and kinetic studies, have been proposed in recent years, suggesting that the morphology of an interplanetary coronal mass ejection (ICME) magnetic cloud can vary from cylindrical, elliptical, toroidal, flattened, pancaked, etc. Recently, Raghav et al. proposed for the first time a unique morphological characteristic of an ICME magnetic cloud at 1 au that showed characteristics of a planar magnetic structure, using in situ data from the ACE spacecraft. In this study, we statistically investigate the plasma properties of planar and nonplanar ICMEs from 1998-2017 at 1 au. The detailed study of 469 ICMEs suggests that 136 (~29%) ICMEs are planar, whereas 333 (~71%) are nonplanar. Furthermore, total interplanetary magnetic field strength, average plasma parameters, i.e., plasma density, beta, thermal pressure, and magnetic pressure in planar ICME, are significantly higher than in the nonplanar ICME. Also, we noticed that the thickness of planar ICMEs is less compared to nonplanar ICMEs. This analysis demonstrates that planar ICMEs are formed due to the high compression of ICME. Moreover, we also observed the southward/northward magnetic field component's double strength during planar ICMEs compared to nonplanar ICMEs. It implies that planar ICMEs are more geoeffective than nonplanar ICMEs.

Keywords: solar coronal mass ejections; solar coronal mass ejection shocks; solar magnetic fields
JWST Reveals a Population of Ultrared, Flattened Galaxies at 2 ≲ z ≲ 6 Previously Missed by HST

With just a month of data, JWST is already transforming our view of the universe, revealing and resolving starlight in unprecedented populations of galaxies. Although "HST-dark" galaxies have previously been detected at long wavelengths, these observations generally suffer from a lack of spatial resolution, which limits our ability to characterize their sizes and morphologies. Here we report on a first view of starlight from a subset of the HST-dark population that is bright with JWST/NIRCam (4.4 μm < 24.5 mag) and very faint or even invisible with HST (<1.6 μm). In this Letter we focus on a dramatic and unanticipated population of physically extended galaxies (≳0.″25). These 12 galaxies have photometric redshifts 2 < z < 6, high stellar masses M ⋆ ≳ 1010 M ⊙, and significant dust-attenuated star formation. Surprisingly, the galaxies have elongated projected axis ratios at 4.4 μm, suggesting that the population is disk dominated or prolate and we hence refer to them as ultrared flattened objects. Most of the galaxies appear red at all radii, suggesting significant dust attenuation throughout. With R e (F444W) ~ 1-2 kpc, the galaxies are similar in size to compact massive galaxies at z ~ 2 and the cores of massive galaxies and S0s at z ~ 0. The stellar masses, sizes, and morphologies of the sample suggest that some could be progenitors of lenticular or fast-rotating galaxies in the local universe. The existence of this population suggests that our previous censuses of the universe may have missed massive, dusty edge-on disks, in addition to dust-obscured starbursts.

Keywords: galaxy evolution; galaxy structure; galaxy formation
Broadband X-Ray Timing and Spectral Characteristics of the Accretion-powered Millisecond X-Ray Pulsar MAXIJ1816-195

We studied the broadband X-ray timing and spectral behaviors of the newly confirmed accreting millisecond X-ray pulsar MAXI J1816-195 during its 2022 outburst. We used data from the Insight-HXMT Medium Energy (ME) and High Energy (HE) telescopes, NICER, and NuSTAR that cover the energy range between 0.8 and 210 keV. A coherent timing analysis of solely the Insight-HXMT HE data across the full outburst revealed a complex behavior of the timing residuals, also prominently visible in the independent Insight-HXMT ME and NICER data, particularly at the rising part of the outburst and at the very end in the NICER data. Therefore, we broke down the full outburst into a (noisy) rising part, covering only about five days, from MJD 59737.0 to 59741.9, and a decaying part, lasting for 19 days across MJD 59741.9-59760.6. Fitting for the decaying part, a timing model including a frequency ν and frequency time derivative $\dot{\nu }$ component yielded a value of (+9.0 ± 2.1) × 10-14 Hz s-1 for $\dot{\nu }$ , which could be interpreted as a spinup under our model assumptions. We detected X-ray pulsations up to ~95 keV in a combination of Insight-HXMT HE observations. The pulse profiles were quite stable over the whole outburst and could be well described by a truncated Fourier series using two harmonics, the fundamental and the first overtone. Both components kept alignment in the range 0.8-64 keV. The joint and time-averaged NICER and Insight-HXMT spectra in the energy range 1-150 keV were well fitted by the absorbed Comptonization model compps plus disk blackbody with two additional Gaussian components. Using the bolometric flux and spinup values both evaluated during the decay phase, we determined a magnetic field strength of (0.2-2) × 108 G for MAXI J1816-195.

Keywords: neutron stars; millisecond pulsars
Exploring Molecular Gas toward the Magellanic Bridge

The Magellanic Bridge (MB) is a diffuse gas structure that connects the Large Magellanic Cloud with the Small Magellanic Cloud. The MB is the closest tidal interaction system between two galaxies to the Milky Way. Taking into account that young stellar objects are embedded in such gaseous structure, it is a unique laboratory to investigate gas dynamics and star formation processes in a very low metallicity environment. In this work we present a preview of the results obtained from observations made with the Atacama Pathfinder Experiment telescope toward some regions of the MB. Through the emission of the 12CO J = 2–1 line we characterize the molecular gas of these regions.

Keywords: magellanic stream; large magellanic cloud; small magellanic cloud
No Consistent Atmospheric Absorption Detected for the Ultra-hot Jupiter WASP-189 b

We observed a partial transit of the ultra-hot Jupiter WASP-189 b with PEPSI on the LBT. We detect a highly variable transit signal in multiple atomic transitions, including H-alpha, Fe I, and Mg I. The signal is not consistent with a transiting planetary atmosphere. We suggest instead that the in-transit signal is due to an inhomogeneous stellar surface. Our observations demonstrate the lack of a highly extended atmosphere in common optical atomic tracers. Although WASP-189 is very bright, atmospheric characterization of the planet will be difficult due to the small transit depth and apparently compact atmosphere.

Keywords: exoplanet atmospheres; exoplanet astronomy
Lithium Evolution of Giant Stars Observed by LAMOST and Kepler

Mapping lithium evolution for evolved stars will provide restrictions and constraints on the fundamental stellar interior physical processes, which will shed further light on our understanding of the theory of stellar structure and evolution. Based on a sample of 1848 giants with known evolutionary phases and lithium abundances from the LAMOST-Kepler and LAMOST-K2 fields, we construct mass-radius diagrams to characterize the evolutionary features of lithium. The stars at red giant branch (RGB) phase show natural depletion along with their stellar evolution; particularly, there are no obvious crowd stars with anomalously high Li abundances near the bump. Most of the low-mass stars reaching their zero-age sequence of core helium burning (ZAHeB) have Li abundances around ~1.0 dex, which shows an increase of Li abundance by ~0.6 dex compared to the stars above the RGB bump. This suggests that helium flash may be responsible for moderate Li production, while for super Li-rich stars, some special mechanisms should be considered during helium flash. Other scenarios, such as mergers, could also be sources given that Li-rich stars can be found at any time during the steady-state phase of core He burning. During the core He-burning (HeB) phase, there is no indication of obvious lithium depletion.

Keywords: stellar evolution; asteroseismology; stellar abundances; lithium stars; chemically peculiar stars; red giant stars; red giant clump