adsabs/SciX_UAT_keywords huggingface dataset:
Gaia EDR3 Parallax Distances to the Great Carina Nebula and Its Star Clusters (Trumpler 14, 15, 16)

Using offset-corrected Gaia EDR3 parallax measurements and spectrophotometric methods, we have determined distances for 69 massive stars in the Carina OB1 association and associated clusters: Trumpler 16 (21 stars), Trumpler 14 (20 stars), Trumpler 15 (three stars), Bochum 11 (five stars), and South Pillars region (20 stars). Past distance estimates to the Carina Nebula range from 2.2 to 3.6 kpc, with uncertainties arising from photometry and anomalous dust extinction. The EDR3 parallax solutions show considerable improvement over DR2, with typical errors σϖ/ϖ ≈ 3%-5%. The O-type stars in the Great Carina Nebula lie at essentially the same distance (2.35 ± 0.08 kpc), quoting mean and rms variance. The clusters have distances of 2.32 ± 0.12 kpc (Tr 16), 2.37 ± 0.15 kpc (Tr 14), 2.36 ± 0.09 kpc (Tr 15), and 2.33 ± 0.12 kpc (Bochum 11) in good agreement with the η Car distance of around 2.3 kpc. O-star proper motions suggest internal (3D) velocity dispersions ~4 km s-1 for Tr 14 and Tr 16. Reliable distances allow estimates of cluster sizes, stellar dynamics, luminosities, and fluxes of photoionizing radiation incident on photodissociation regions in the region. We estimate that Tr 14 and Tr 16 have half-mass radii rh = 1.5-1.8 pc, stellar crossing times tcr = rh/vm ≈ 0.7-0.8 Myr, and two-body relaxation times trh ≈ 40-80 Myr. The underlying velocity dispersion for Tr 14, if a bound cluster, would be ${v}_{{\rm{m}}}\approx {2.1}_{-0.4}^{+0.7}$ km s-1 for $N={7600}_{-2600}^{+5800}$ stars. With the higher dispersions of the O stars, inward drift would occur slowly, on timescales of 3-6 Myr.

Keywords: massive stars; open star clusters; stellar dynamics; parallax; stellar parallax
Near-core Acoustic Glitches Are Not Oscillatory: Consequences for Asteroseismic Probes of Convective Boundary Mixing

Asteroseismology has been used extensively in recent years to study the interior structure and physical processes of main-sequence stars. We consider prospects for using pressure modes (p-modes) near the frequency of maximum oscillation power to probe the structure of the near-core layers of main-sequence stars with convective cores by constructing stellar model tracks. Within our mass range of interest, the inner turning point of p-modes as determined by the Jeffreys-Wentzel-Kramers-Brillouin (JWKB) approximation evolves in two distinct phases during the main sequence, implying a sudden loss of near-core sensitivity during the discontinuous transition between the two phases. However, we also employ non-JWKB asymptotic analysis to derive a contrasting set of expressions for the effects that these structural properties will have on the mode frequencies, which do not encode any such transition. We show analytically that a sufficiently near-core perturbation to the stellar structure results in nonoscillatory, degree-dependent perturbations to the star's oscillation mode frequencies, contrasting with the case of an outer glitch. We also demonstrate numerically that these near-core acoustic glitches exhibit strong angular degree dependence, even at low degree, agreeing with the non-JWKB analysis, rather than the degree-independent oscillations that emerge from JWKB analyses. These properties have important implications for using p-modes to study near-core mixing processes for intermediate-mass stars on the main sequence, as well as for the interpretation of near-center acoustic glitches in other astrophysical configurations, such as red giants.

Keywords: asteroseismology; stellar physics; stellar evolution; main sequence
About Metallicity Variations in the Local Galactic Interstellar Medium

In this paper we discuss and confront recent results on metallicity variations in the local interstellar medium, obtained from observations of H II regions and neutral clouds of the Galactic thin disk, and compare them with recent high-quality metallicity determinations of other tracers of the chemical composition of the interstellar medium as B-type stars, classical Cepheids, and young clusters. We find that the metallicity variations obtained for these last kinds of objects are consistent with each other and with that obtained for H II regions but significantly smaller than those obtained for neutral clouds. We also discuss the presence of a large population of low-metallicity clouds as the possible origin for large metallicity variations in the local Galactic thin disk. We find that such a hypothesis does not seem compatible with: (a) what is predicted by theoretical studies of gas mixing in galactic disks, and (b) the models and observations on the metallicity of high-velocity clouds and their evolution as they mix with the surrounding medium in their fall onto the Galactic plane. We conclude that most of the evidence favors that the chemical composition of the interstellar medium in the solar neighborhood is highly homogeneous.

Keywords: galaxy abundances; galaxy evolution; interstellar abundances; h ii regions; interstellar clouds
Visual Orbits of Spectroscopic Binaries with the CHARA Array. III. HD 8374 and HD 24546

We present the visual orbits of two long-period spectroscopic binary stars, HD 8374 and HD 24546, using interferometric observations acquired with the CHARA Array and the Palomar Testbed Interferometer. We also obtained new radial velocities from echelle spectra using the APO 3.5 m and Fairborn 2.0 m telescopes. By combining the visual and spectroscopic observations, we solve for the full, three-dimensional orbits and determine the stellar masses and distances to within 3% uncertainty. We then estimate the effective temperature and radius of each component star through Doppler tomography and spectral energy distribution analyses, in order to compare the observed stellar parameters to the predictions of stellar evolution models. For HD 8374, we find masses of M1 = 1.636 ± 0.050M⊙ and M2 = 1.587 ± 0.049M⊙, radii of R1 = 1.84 ± 0.05R⊙ and R2 = 1.66 ± 0.12R⊙, temperatures of ${T}_{\mathrm{eff}1}=7280\pm 110$ K and ${T}_{\mathrm{eff}2}=7280\pm 120$ K, and an estimated age of 1.0 Gyr. For HD 24546, we find masses of M1 = 1.434 ± 0.014M⊙ and M2 = 1.409 ± 0.014M⊙, radii of R1 = 1.67 ± 0.06R⊙ and R2 = 1.60 ± 0.10R⊙, temperatures of ${T}_{\mathrm{eff}1}=6790\pm 120$ K and ${T}_{\mathrm{eff}2}=6770\pm 90$ K, and an estimated age of 1.4 Gyr. HD 24546 is therefore too old to be a member of the Hyades cluster, despite its physical proximity to the group.

Keywords: spectroscopic binary stars; visual binary stars; fundamental parameters of stars
Identifying Interstellar Object Impact Craters

The discoveries of two interstellar objects (ISOs) in recent years have generated significant interest in constraining their physical properties and the mechanisms behind their formation. However, their ephemeral passages through our solar system permitted only incomplete characterization. We investigate avenues for identifying craters that may have been produced by ISOs impacting terrestrial solar system bodies, with particular attention toward the Moon. A distinctive feature of ISOs is their relatively high encounter velocity compared to asteroids and comets. Local stellar kinematics indicate that terrestrial solar system bodies should have experienced of order unity ISO impacts exceeding 100 km s-1. By running hydrodynamical simulations for projectiles of different masses and impact velocities up to 100 km s-1, we show how late-stage equivalence dictates that transient crater dimensions alone are insufficient for inferring the projectile's velocity. On the other hand, the melt volume within craters of a fixed diameter may be a potential route for identifying ISO craters, as faster impacts produce more melt. This method requires that the melt volume scales with the energy of the projectile while the crater diameter scales with the point-source limit (subenergy). Given that there are probably only a few ISO craters in the solar system at best, and that transient crater dimensions are not a distinguishing feature for impact velocities, at least up to 100 km s-1, identification of an ISO crater proves a challenging task. Melt volume and high-pressure petrology may be diagnostic features once large volumes of material can be analyzed in situ.

Keywords: interstellar objects; impact phenomena; hydrodynamical simulations
Revisiting the Spectral Energy Correlations of GRBs with Fermi Data. I. Model-wise Properties

Gamma-ray bursts (GRBs) exhibit a diversity of spectra. Several spectral models (e.g., Band, cutoff power law (CPL), and blackbody) and their hybrid versions (e.g., Band+blackbody) have been widely used to fit the observed GRB spectra. Here, we attempt to collect all the bursts detected by Fermi/GBM with known redshifts from 2008 July to 2022 May, having been motivated to (i) provide a parameter catalog independent of the official Fermi/GBM team and (ii) achieve a "clean" model-based GRB spectral energy correlation analysis. A nearly complete GRB sample is created, containing 153 such bursts (136 long GRBs and 17 short GRBs). Using the sample and by performing detailed spectral analysis and model comparisons, we investigate two GRB spectral energy correlations: the correlation of the cosmological rest-frame peak energy (E p,z ) of the ν F ν prompt emission spectrum with (i) the isotropic-bolometric-equivalent emission energy E γ,iso (the Amati relation) and (ii) the isotropic-bolometric-equivalent peak luminosity L p,iso (the Yonetoku relation). From a linear regression analysis, a tight correlation between E p,z and E γ,iso (and L γ,iso) is found for both Band-like and CPL-like bursts (except for CPL-like long burst E p,z -E γ,iso correlation). More interestingly, CPL-like bursts do not fall on the Band-like burst Amati and Yonetoku correlations, suggesting distinct radiation processes, and pointing to the fact that these spectral energy correlations are tightly reliant on the model-wise properties.

Keywords: gamma-ray bursts
Deep Hubble Space Telescope Imaging on the Extended Lyα Emission of a QSO at z = 2.19 with a Damped Lyman Alpha System as a Natural Coronagraph

Recent observations suggest that proximate damped Lyα (PDLA) systems can be used to study the host galaxies of quasi-stellar objects (QSOs), because the PDLAs can block the bright point-spread function from central QSOs. Using six orbits of narrowband imaging with Hubble Space Telescope (HST)/WFC3, we present the first high-resolution narrowband image of the Lyα emission in the PDLA trough of the QSO SDSS J115432.67-021537.9. We detect one major component and one minor component in the narrowband imaging. Combining the ${HST}$ /WFC3 imaging with deep Magellan/MagE spectra, we measure that the Lyα flux ${F}_{\mathrm{Ly}\alpha }$ = $1.56\pm 0.10\,\times {10}^{-16}\,\mathrm{erg}\,{{\rm{s}}}^{-1}\,{\mathrm{cm}}^{-2}$ , which is among the luminous (≈2.7 ${\text{}}{L}_{\mathrm{Ly}\alpha }^{\star }$ ) Lyα emitters at $z=$ 2.19. The $\mathrm{Ly}\alpha $ -based star formation rate is ∼7 ${M}_{\odot }\,{\mathrm{yr}}^{-1}$ . These observational results favor that the star formation from the host galaxy could be the main mechanism powering the Lyα emission. This new method sheds light on the study of the kinematic structure and the spatial distribution of the extended Lyα emitting regions around the QSO host.

Keywords: quasars; quasar absorption line spectroscopy
Magnetic Relaxation Seen in a Rapidly Evolving Light Bridge in a Sunspot

We report a magnetic relaxation process inside a sunspot associated with the evolution of a transient light bridge (LB). From high-resolution imaging and spectro-polarimetric data taken by the 1.6 m Goode Solar Telescope installed at Big Bear Solar Observatory, we observe the evolutionary process of a rapidly evolving LB. The LB is formed as a result of the strong intrusion of filamentary structures with relatively horizontal fields into the vertical umbral field region. A strong current density is detected along a localized region where the magnetic field topology changes rapidly in the sunspot, especially in the boundary region between the LB and the umbra, and bright jets are observed intermittently and repeatedly in the chromosphere along this region through magnetic reconnection. In the second half of our observation, the horizontal component of the magnetic field diminishes within the LB, and the typical convection structure within the sunspot, which manifests itself as umbral dots, is restored. Our findings provide a comprehensive perspective not only on the evolution of an LB itself but also on its impacts in the neighboring regions, including the chromospheric activity and the change of magnetic energy of a sunspot.

Keywords: sunspots; solar chromosphere; solar magnetic fields; solar magnetic reconnection
Intermittency of Fast MHD Modes and Regions of Anomalous Gradient Orientation in Low-β Plasmas

The strong alignment of small-scale turbulent Alfvénic motions with the direction of magnetic field that percolates the small-scale eddies and imprints the direction of the magnetic field is a property that follows from the MHD theory and the theory of turbulent reconnection. The Alfvénic eddies mix magnetic fields perpendicular to the direction of the local magnetic field, and this type of motion is used to trace magnetic fields with the velocity gradient technique (VGT). The other type of turbulent motion, fast modes, induces anisotropies orthogonal to Alfvénic eddies and interferes with the tracing of the magnetic field with the VGT. We report a new effect, i.e., in a magnetically dominated low-β subsonic medium, fast modes are very intermittent, and in a volume with a small filling factor the fast modes dominate other turbulent motions. We identify these localized regions as the cause of the occasional change of direction of gradients in our synthetic observations. We show that the new technique of measuring the gradients of gradient amplitudes suppresses the contribution from the fast-mode-dominated regions, improving the magnetic field tracing. In addition, we show that the distortion of the gradient measurements by fast modes is also applicable to the synchrotron intensity gradients, but the effect is reduced compared to the VGT.

Keywords: interstellar magnetic fields; interstellar medium; interstellar dynamics
Likelihood-free Inference with the Mixture Density Network

In this work, we propose using the mixture density network (MDN) to estimate cosmological parameters. We test the MDN method by constraining parameters of the ΛCDM and wCDM models using Type Ia supernovae and the power spectra of the cosmic microwave background. We find that the MDN method can achieve the same level of accuracy as the Markov Chain Monte Carlo method, with a slight difference of ${ \mathcal O }({10}^{-2}\sigma )$ . Furthermore, the MDN method can provide accurate parameter estimates with ${ \mathcal O }({10}^{3})$ forward simulation samples, which are useful for complex and resource-consuming cosmological models. This method can process either one data set or multiple data sets to achieve joint constraints on parameters, extendable for any parameter estimation of complicated models in a wider scientific field. Thus, the MDN provides an alternative way for likelihood-free inference of parameters.

Keywords: cosmological parameters; observational cosmology; computational methods; astronomy data analysis; neural networks
NGC 6302: The Tempestuous Life of a Butterfly

NGC 6302 (The Butterfly Nebula) is an extremely energetic and rapidly expanding bipolar planetary nebula (PN). If the central source is a single star, then its apparent location in an H-R diagram places it among the most massive, hottest, and presumably rapidly evolving of all central stars of PNe. Our proper motion study of NGC 6302, based on Hubble Space Telescope WFC3 images spanning 11 yr, has uncovered at least four different pairs of uniformly expanding internal lobes ejected at various times and orientations over the past two millennia at speeds ranging from 10-600 km s-1. In addition, we find a pair of collimated off-axis flows in constant motion at ~770 ± 100 km s-1 within which bright [Fe II] feathers are conspicuous. Combining our results with those previously published, we find that the ensemble of flows has an ionized mass >0.1 M ⊙ and its kinetic energy, between 1046 and 1048 erg, lies at the upper end of gravity-powered PNe ejection processes such as stellar mergers or mass accretion. We assemble our results into a plausible historical timeline of ejections from the nucleus and suggest that the ejections are powered by gravitational infall.

Keywords: planetary nebulae; bipolar nebulae; ejecta; stellar wind bubbles; shocks
KMTNet Nearby Galaxy Survey. III. Deficient Hα Flux in the Extended Disks of Spiral Galaxies

We perform a deep, wide-field imaging survey of nearby galaxies using Hα and broadband filters to investigate the characteristics of star formation in galaxies. Motivated by the finding that star formation rates (SFRs) derived from Hα fluxes in dwarf galaxies are systematically lower than those inferred from far-ultraviolet (FUV) fluxes, we attempt to determine whether the same trend exists in the extended disks of two star-forming galaxies. We perform spatially resolved photometry using grid-shaped apertures to measure the FUV and Hα fluxes of star-forming regions. We also perform spectral energy distribution (SED) fittings using 11 photometric data points (FUV-to-MIR), including data from the literature, to estimate the local properties such as internal attenuation of individual star-forming clumps. Comparing SFRFUV and SFRHα, which are converted from the Hα and FUV fluxes corrected for the local properties, we find that SFRHα/SFRFUV tend to decrease as the SFR decreases. We evaluate possible causes of this discrepancy between the two SFRs by restricting parameters in the SED fitting and conclude that deficient Hα fluxes in the extended disks of galaxies are tightly correlated with recent starbursts. The strong and short starburst, which has been rapidly suppressed over the last 10 Myr, seems to induce a significant discrepancy between the SFRHα and SFRFUV. In addition, the recent bursts in the extended disks of galaxies appear to have occurred azimuth-symmetrically, implying that these were likely triggered by gas accretion or internal processes rather than external perturbation.

Keywords: galaxies; galaxy properties; star formation; photometry
A Multiwavelength Study of the Formation of the AFGL 333-Ridge

We presented a multiwavelength study of the AFGL 333-Ridge. The molecular line data reveals that the AFGL 333-Ridge has two independent velocity components at -50.5 and -48.0 km s-1. In the position-velocity diagram, the bridge feature connects with two parts that are spatially correlated but separated in velocity. This observational evidence supports the scenario that the two velocity components have collided and merged into one molecular cloud. The majority of Class I young stellar objects (YSOs) are distributed within the collision region, suggesting that the cloud-cloud collision has induced the YSOs' formation in the ridge. Using the radio recombination line (RRL) data obtained by the Five-hundred-meter Aperture Spherical radio Telescope, the RRL velocities of three H II regions are consistent with that of the AFGL 333-Ridge. By comparing the three H II regions' dynamical ages with the collision timescale of the two components, we conclude that the influence of the three H II regions may not drive the two clouds to merge. The formation of the AFGL 333-Ridge is probably due to the expansion of the giant H II region W4.

Keywords: interstellar filaments; h ii regions
Preliminary Target Selection for the DESI Quasar (QSO) Sample

The DESI survey will measure large-scale structure using quasars as direct tracers of dark matter in the redshift range 0.9 < z < 2.1 and using quasar Lyα forests at z > 2.1. We present two methods to select candidate quasars for DESI based on imaging in three optical (g, r, z) and two infrared (W1, W2) bands. The first method uses traditional color cuts and the second utilizes a machine-learning algorithm.

Keywords: quasars; redshift surveys; large-scale structure of the universe
Spectral Signatures of Chromospheric Condensation in a Major Solar Flare

We study the evolution of chromospheric line and continuum emission during the impulsive phase of the X-class SOL2014-09-10T17:45 solar flare. We extend previous analyses of this flare to multiple chromospheric lines of Fe I, Fe II, Mg II, C I, and Si II observed with the Interface Region Imaging Spectrograph, combined with radiative-hydrodynamical (RHD) modeling. For multiple flaring kernels, the lines all show a rapidly evolving double-component structure: an enhanced emission component at rest, and a broad, highly redshifted component of comparable intensity. The redshifted components migrate from 25 to 50 km s-1 toward the rest wavelength within ∼30 s. Using Fermi hard X-ray observations, we derive the parameters of an accelerated electron beam impacting the dense chromosphere, using them to drive an RHD simulation with the RADYN code. As in Kowalski et al. (2017), our simulations show that the most energetic electrons penetrate into the deep chromosphere, heating it to T ∼ 10,000 K, while the bulk of the electrons dissipate their energy higher, driving an explosive evaporation, and its counterpart condensation—a very dense (ne ∼ 2 × 1014 cm-3), thin layer (30-40 km thickness), heated to 8-12,000 K, moving toward the stationary chromosphere at up to 50 km s-1. The synthetic Fe II 2814.45 Å profiles closely resemble the observational data, including a continuum enhancement, and both a stationary and a highly redshifted component, rapidly moving toward the rest wavelength. Importantly, the absolute continuum intensity, ratio of component intensities, relative time of appearance, and redshift amplitude are sensitive to the model input parameters, showing great potential as diagnostics.

Keywords: solar flares; solar chromosphere; solar activity; radiative transfer simulations; solar ultraviolet emission
Tether-cutting and Overlying Magnetic Reconnections in an MHD Simulation of Prominence-cavity System

We investigate the magnetic reconnection in an MHD simulation of a coronal magnetic flux rope (MFR) confined by a helmet streamer, where a prominence-cavity system forms. This system includes a hot cavity surrounding a prominence with prominence horns and a central hot core above the prominence. The evolution of the system from quasi-equilibrium to eruption can be divided into four phases: quasi-static, slow-rise, fast-rise, and propagation phases. The emerged MFR initially stays quasi-static and magnetic reconnection occurs at the overlying high-Q (squashing factor) apex region, which gradually evolves into a hyperbolic flux tube (HFT). The decrease of the integrated magnetic tension force (above the location of the overlying reconnection) is due to the removal of overlying confinement by the enhanced overlying reconnection between the MFR and the overlying fields at the apex HFT, thus engines the slow rise of the MFR with a nearly constant velocity. Once the MFR reaches the regime of torus instability, another HFT immediately forms at the dip region under the MFR, followed by the explosive flare reconnection. The integrated resultant force (above the location of the flare reconnection) exponentially increases, which drives the exponential fast rise of the MFR. The system enters the propagation phase, once its apex reaches the height of about one solar radius above the photosphere. The simulation reproduces the main processes of one group of prominence eruptions especially those occurring on the quiet Sun.

Keywords: solar coronal mass ejections; solar filaments; solar prominences; magnetohydrodynamical simulations; solar magnetic fields; solar magnetic reconnection