adsabs/SciX_UAT_keywords huggingface dataset:
Detection of Solar-like Oscillations in Subgiant and Red Giant Stars Using 2 minute Cadence TESS Data

Based on all 2 minute cadence TESS light curves from Sector 1 to 60, we provide a catalog of 8651 solar-like oscillators, including frequency at maximum power ( ${\nu }_{\max }$ , with its median precision σ = 5.39%), large frequency separation (Δν, σ = 6.22%), and seismically derived masses, radii, and surface gravity values. In this sample, we have detected 2173 new oscillators and added 4373 new Δν measurements. Our seismic parameters are consistent with those from Kepler, K2, and previous TESS data. The median fractional residual in ${\nu }_{\max }$ is 1.63%, with a scatter of 14.75%, and in Δν it is 0.11%, with a scatter of 10.76%. We have detected 476 solar-like oscillators with ${\nu }_{\max }$ exceeding the Nyquist frequency of Kepler long-cadence data during the evolutionary phases of subgiants and the base of the red giant branch, which provide a valuable resource for understanding angular momentum transport.

Keywords: asteroseismology; subgiant stars; red giant stars; light curves
Dissecting the Mid-infrared Heart of M83 with JWST

We present a first look at the MRS observations of the nucleus of the nearby galaxy M83, taken with MIRI on board JWST. The observations show a rich set of emission features from the ionized gas, warm molecular gas, and dust. To begin dissecting the complex processes in this part of the galaxy, we divide the observations into four different regions. We find that the strength of the emission features varies strongly from region to region, with the southeast region displaying the weakest features tracing the dust continuum and interstellar medium (ISM) properties. Comparison between the cold molecular gas traced by the 12CO (1-0) transition with the Atacama Large Millimeter/submillimeter Array and the H2 S(1) transition shows a similar spatial distribution. This is in contrast to the distribution of the much warmer H2 emission from the S(7) transition found to be concentrated around the optical nucleus. We use the rotational emission lines and model the H2 excitation to estimate a total molecular gas mass accounting for the warm H2 component of M(>50 K) ${}_{{{\rm{H}}}_{2}}$ = 67.90 (±5.43) × 106 M ⊙. We compare this value to the total gas mass inferred by probing the cold H2 gas through the 12CO (1-0) emission, M(CO) ${}_{{{\rm{H}}}_{2}}$ = 17.15 × 106 M ⊙. We estimate that ~75% of the total molecular gas mass is contained in the warm H2 component. We also identify [O IV] 25.89 μm and [Fe II] 25.99 μm emission. We propose that the diffuse [Fe II] 25.99 μm emission might be tracing shocks created during the interactions between the hot wind produced by the starburst and the much cooler ISM above the galactic plane. More detailed studies are needed to confirm such a scenario.

Keywords: starburst galaxies; interstellar medium; molecular gas
A Fully Self-consistent Model for Solar Flares

The "standard solar flare model" collects all physical ingredients identified by multiwavelength observations of our Sun: magnetic reconnection, fast particle acceleration, and the resulting emission at various wavelengths, especially in soft to hard X-ray channels. Its cartoon representation is found throughout textbooks on solar and plasma astrophysics and guides interpretations of unresolved energetic flaring events on other stars, accretion disks, and jets. To date, a fully self-consistent model that reproduces the standard scenario in all its facets is lacking, since this requires the combination of a large-scale, multidimensional magnetohydrodynamic (MHD) plasma description with a realistic fast electron treatment. Here we demonstrate such a novel combination, where MHD combines with an analytic fast electron model, adjusted to handle time-evolving, reconnecting magnetic fields and particle trapping. This allows us to study (1) the role of fast electron deposition in the triggering of chromospheric evaporation flows, (2) the physical mechanisms that generate various hard X-ray sources at chromospheric footpoints or looptops, and (3) the relationship between soft X-ray and hard X-ray fluxes throughout the entire flare loop evolution. For the first time, this self-consistent solar flare model demonstrates the observationally suggested relationship between flux swept out by the hard X-ray footpoint regions and the actual reconnection rate at the X-point, which is a major unknown in flaring scenarios. We also demonstrate that a looptop hard X-ray source can result from fast electron trapping.

Keywords: solar flares; x-ray sources
Discovery of the Exceptionally Short Period Ultracool Dwarf Binary LP 413-53AB

We report the detection of large-amplitude, rapid radial velocity (RV) variations and line-splitting in high-resolution Keck/NIRSPEC spectra of the M9 dwarf LP 413-53. We attribute these features to binary motion. Analyzing data spanning 15 yr, we infer a preliminary orbital period of 0.7106156 ± 0.0000002 days, an eccentricity of 0.0088 ± 0.0017, a primary RV semiamplitude of 23.70 ± 0.05 km s-1, and a secondary RV semiamplitude of 28.41 ± 0.06 km s-1, implying a system mass ratio M secondary/M primary = 0.8340 ± 0.0017. These measurements identify LP 413-53 as the shortest-period ultracool binary discovered to date, and one of the smallest separation main-sequence binaries known. The position and velocity of the system rule out previously reported membership in the Hyades Moving Group, and indicate that this is likely a pair of evolved (age ≳1 Gyr), very-low-mass stars. Assuming masses consistent with evolved late-M and L dwarfs, we estimate an orbital separation of 0.0081-0.0084 au or 17-19 stellar radii, and an orbital inclination angle of 24°, making it unlikely that this system exhibits eclipse events. The larger radii of these stars at young ages would have put them near contact at the system's current separation, and we speculate that this system has undergone dynamical evolution, either through orbital angular momentum loss or ejection of a third component followed by tidal circularization. While further observations are needed to fully constrain the orbital and physical parameters of LP 413-53, this ultra-short-period ultracool dwarf binary system serves as a new test bed for formation and dynamical evolution models of very-low-mass multiples.

Keywords: close binary stars; m dwarf stars; spectroscopic binary stars; low mass stars; high resolution spectroscopy
A Comparative Modeling Study of the Seasonal, Temporal, and Spatial Distribution of Meteoroids in the Upper Atmospheres of Venus, Earth, and Mars

The meteoroid input function (MIF) describes the seasonal, diurnal and planetographic distribution of incoming meteoroids onto an atmosphere and/or surface of a solar system body. Utilizing state-of-the-art dynamical models of the main populations of meteoroids, we present a comparative study of the MIF on the atmospheres of Venus, Earth and Mars. Our modeling results show that, although a planet's axial tilt and orbital eccentricity introduce measurable important variability of the overall MIF, excursions from the ecliptic plane due to orbital inclination are responsible for the largest differences, producing variations of up to 40% with respect to the mean value in the overall mass fluxes of Venus and Mars. This is particularly true for meteoroid populations concentrated around the ecliptic plane, which are believed to be the dominant source of organics and metals on the atmospheres of these planets.

Keywords: meteoroids; planetary atmospheres; meteor radiants
Herbig Ae/Be Stars toward the Dark Cloud LDN 1667

We report the discovery of a new emission-line object, named SPH 4-South = (GAIA EDR3 5616553300192230272), toward the dark cloud LDN 1667. This object came to our attention after inspecting public images that show a faint diffuse nebula a few arcseconds south of SPH 4, an emission-line object previously classified as a T Tauri star. We present high-resolution spectra and analyzed JHK photometry of SPH 4 and SPH 4-South and new narrowband and archival broadband images of these objects. A comparison of the spectra of SPH 4 and SPH 4-South with high-resolution ones of DG Cir and R Mon strongly suggests that SPH 4 and SPH 4-South are Herbig Ae/Be stars. The classification of SPH 4-South is further supported by using a k-NN algorithm to its position in an H-K versus J-H color-color diagram. Both stars are detected in the four WISE bands and the WISE colors allow us to classify SPH 4 as a Class I and SPH 4-South as a Class II source. We also show that the faint nebula is most probably associated with SPH 4-South. Using published results on LDN 1667 and the Gaia Early Data Release 3, we conclude that SPH 4 is a member of LDN 1667. The case of SPH 4-South is not clear because the determination of its distance and proper motion could be affected by the nebulosity around the star, although membership of SPH 4-South to LDN 1667 cannot be ruled out. * Based on the observations made with the 2.2 m telescope at the European Southern Observatory (La Silla, Chile) under the agreement between Observatório Nacional (Brazil) and European Southern Observatory (ESO) and also under the agreement between Observatório Nacional (Brazil) and Max Planck Institut für Astronomie (MPG) and also based on observations at Centro Astronómico Hispano Alemán (CAHA) at Calar Alto operated jointly by Instituto de Astrofísica de Andalucía (CSIC) and Max Planck Institut für Astronomie (MPG). Centro Astronómico Hispano en Andalucía is now operated by Instituto de Astrofísica de Andalucía and Junta de Andalucía.

Keywords: stellar evolution; early stellar evolution
Probing Turbulent Scattering Effects on Suprathermal Electrons in the Solar Wind: Modeling, Observations, and Implications

This study explores the impact of a turbulent scattering mechanism, akin to those influencing solar and galactic cosmic rays propagating in the interplanetary medium, on the population of suprathermal electrons in the solar wind. We employ a Fokker–Planck equation to model the radial evolution of electron pitch angle distributions under the action of magnetic focusing, which moves the electrons away from isotropy, and of a diffusion process that tends to bring them back to it. We compare the steady-state solutions of this Fokker–Planck equation with data obtained from the Solar Orbiter and Parker Solar Probe missions and find a remarkable agreement, varying the turbulent mean free path as the sole free parameter in our model. The obtained mean free paths are of the order of the astronomical unit, and display weak dependence on electron energy within the 100 eV–1 keV range. This value is notably lower than Coulomb collision estimates but aligns well with observed mean free paths of low-rigidity solar energetic particle events. The strong agreement between our model and observations leads us to conclude that the hypothesis of turbulent scattering at work on electrons at all heliospheric distances is justified. We discuss several implications, notably the existence of a low Knudsen number region at large distances from the Sun, which offers a natural explanation for the presence of an isotropic "halo" component at all distances from the Sun—electrons being isotropized in this distant region before traveling back into the inner part of the interplanetary medium.

Keywords: solar wind; solar energetic particles; space plasmas; interplanetary physics
Characterization of High-polarization Stars and Blazars with DIPOL-1 at Sierra Nevada Observatory

We report here the performance and first results of the new multiband optical polarimeter DIPOL-1, installed at the Sierra Nevada Observatory 90 cm T90 telescope (SNO, Granada, Spain). DIPOL-1 is equipped with a plane parallel calcite plate and λ/2 retarder for modulating the intensity of two perpendicularly polarized beams, and a high readout speed CMOS camera that allows for fast, time-dense coverage. We characterize the performance of this instrument through a series of tests on zero- and high-polarization standard stars. The instrumental polarization in the Nasmyth focus was well determined, with a very stable contribution of 4.0806% ± 0.0014% in the optical R band. For bright high-polarization standards (m R < 8) we reach precisions <0.02% in polarization degree and 0.°1 in polarization angle for exposures of 2–4 min. The polarization properties of these stars have been constrained, providing more recent results also about possible variability for future studies of some of the most used calibrators. Moreover, we have tested the capability of observing much fainter objects, in particular through blazar observations, where we reach a precision of <0.5%‑0.6% and <0.°5 for faint targets (m R ∼ 16.5) with exposures of ∼1 hr. For brighter targets (m R ∼ 14.5‑15), we can aim for time-dense observations with errors <0.2%‑0.4% and <1°‑1.°5 in 5–20 min. We have successfully performed a first campaign with DIPOL-1, detecting significant polarized emission of several blazars, with special attention to the highest ever polarization degree measured from blazar 3C 345 at ∼32%.

Keywords: polarimeters; polarimetry; blazars; jets; high energy astrophysics; observational astronomy
Milky Way Satellite Census. I. The Observational Selection Function for Milky Way Satellites in DES Y3 and Pan-STARRS DR1

We report the results of a systematic search for ultra-faint Milky Way satellite galaxies using data from the Dark Energy Survey (DES) and Pan-STARRS1 (PS1). Together, DES and PS1 provide multi-band photometry in optical/near-infrared wavelengths over ∼80% of the sky. Our search for satellite galaxies targets ∼25,000 deg2 of the high-Galactic-latitude sky reaching a 10σ point-source depth of ≳22.5 mag in the g and r bands. While satellite galaxy searches have been performed independently on DES and PS1 before, this is the first time that a self-consistent search is performed across both data sets. We do not detect any new high-significance satellite galaxy candidates, recovering the majority of satellites previously detected in surveys of comparable depth. We characterize the sensitivity of our search using a large set of simulated satellites injected into the survey data. We use these simulations to derive both analytic and machine-learning models that accurately predict the detectability of Milky Way satellites as a function of their distance, size, luminosity, and location on the sky. To demonstrate the utility of this observational selection function, we calculate the luminosity function of Milky Way satellite galaxies, assuming that the known population of satellite galaxies is representative of the underlying distribution. We provide access to our observational selection function to facilitate comparisons with cosmological models of galaxy formation and evolution.

Keywords: dwarf spheroidal galaxies; local group; dark matter; milky way galaxy
Identification of Single Spectral Lines in Large Spectroscopic Surveys Using UMLAUT: an Unsupervised Machine-learning Algorithm Based on Unbiased Topology

The identification of an emission line is unambiguous when multiple spectral features are clearly visible in the same spectrum. However, in many cases, only one line is detected, making it difficult to correctly determine the redshift. We developed a freely available unsupervised machine-learning algorithm based on unbiased topology (UMLAUT) that can be used in a very wide variety of contexts, including the identification of single emission lines. To this purpose, the algorithm combines different sources of information, such as the apparent magnitude, size and color of the emitting source, and the equivalent width and wavelength of the detected line. In each specific case, the algorithm automatically identifies the most relevant ones (i.e., those able to minimize the dispersion associated with the output parameter). The outputs can be easily integrated into different algorithms, allowing us to combine supervised and unsupervised techniques and increasing the overall accuracy. We tested our software on WISP (WFC3 IR Spectroscopic Parallel) survey data. WISP represents one of the closest existing analogs to the near-IR spectroscopic surveys that are going to be performed by the future Euclid and Roman missions. These missions will investigate the large-scale structure of the universe by surveying a large portion of the extragalactic sky in near-IR slitless spectroscopy, detecting a relevant fraction of single emission lines. In our tests, UMLAUT correctly identifies real lines in 83.2% of the cases. The accuracy is slightly higher (84.4%) when combining our unsupervised approach with a supervised approach we previously developed.

Keywords: spectroscopy; algorithms; spectral line identification; redshift surveys
Empirical Calibration of the Reddening Maps in the Magellanic Clouds

We present reddening maps of the Large Magellanic Cloud (LMC) and Small Magellanic Cloud (SMC), based on color measurements of the red clump. Reddening values of our maps were obtained by calculating the difference of the observed and intrinsic color of the red clump in both galaxies. To obtain the intrinsic color of the red clump, we used reddenings obtained from late-type eclipsing binary systems, measurements for blue supergiants and reddenings derived from Strömgren photometry of B-type stars. We obtained intrinsic color of the red clump (V - I)0 = 0.838 ± 0.034 mag in the LMC, and (V - I)0 = 0.814 ± 0.034 mag in the SMC. We prepared our map with 3' resolution, covering the central part of the LMC and SMC. The mean value of the reddening is E(B - V)LMC = 0.127 mag and E(B - V)SMC = 0.084 mag for the LMC and SMC, respectively. The systematic uncertainty of the average reddening value assigned to each field of our maps is 0.013 mag for both Magellanic Clouds. Our reddening values are on average higher by 0.061 mag for the LMC and 0.054 mag for the SMC, compared with the maps of Haschke et al. We also compared our values with different types of reddening tracers. Cepheids, RR Lyrae stars, early-type eclipsing binaries, and other reddening estimations based on the red clump color on average show reddenings consistent with our map to within a few hundredths of magnitude.

Keywords: interstellar dust extinction; magellanic clouds; reddened stars
A New Candidate Luminous Blue Variable

We identify IRAS 16115-5044, which was previously classified as a protoplanetary nebula (PPN), as a candidate luminous blue variable (LBV). The star has high luminosity (≳105.75 L⊙), ensuring supergiant status, has a temperature similar to LBVs, is photometrically and spectroscopically variable, and is surrounded by warm dust. Its near-infrared spectrum shows the presence of several lines of H I, He I, Fe II, Fe [II], Mg II, and Na I with shapes ranging from pure absorption and P Cygni profiles to full emission. These characteristics are often observed together in the relatively rare LBV class of stars, of which only ≈20 are known in the Galaxy. The key to the new classification is the fact that we compute a new distance and extinction that yield a luminosity significantly in excess of those for post-AGB PPNe, for which the initial masses are <8 M⊙. Assuming single star evolution, we estimate an initial mass of ≈40 M⊙.

Keywords: luminous blue variable stars; stellar evolution; massive stars; supergiant stars; stellar mass loss
Eruption of a Magnetic Flux Rope in a Comprehensive Radiative Magnetohydrodynamic Simulation of Flare-productive Active Regions

Radiative magnetohydrodynamic simulation includes sufficiently realistic physics to allow for the synthesis of remote sensing observables that can be quantitatively compared with observations. We analyze the largest flare in a simulation of the emergence of large flare-productive active regions described by Chen et al. The flare releases 4.5 × 1031 erg of magnetic energy and is accompanied by a spectacular coronal mass ejection. Synthetic soft X-ray flux of this flare reaches M2 class. The eruption reproduces many key features of observed solar eruptions. A preexisting magnetic flux rope is formed along the highly sheared polarity inversion line between a sunspot pair and is covered by an overlying multipole magnetic field. During the eruption, the progenitor flux rope actively reconnects with the canopy field and evolves to the large-scale multithermal flux rope that is observed in the corona. Meanwhile, the magnetic energy released via reconnection is channeled down to the lower atmosphere and gives rise to bright soft X-ray post-flare loops and flare ribbons that reproduce the morphology and dynamic evolution of observed flares. The model helps to shed light on questions of where and when the a flux rope may form and how the magnetic structures in an eruption are related to observable emission properties.

Keywords: solar active region magnetic fields; solar extreme ultraviolet emission; active solar corona; solar flares; solar coronal mass ejections; radiative magnetohydrodynamics; magnetohydrodynamical simulations
An Evolution and Eruption of the Coronal Magnetic Field through a Data-driven MHD Simulation

We present a newly developed data-driven magnetohydrodynamics (MHD) simulation code under a zero-β approximation based on a method proposed by Hayashi et al. 2018 and 2019. Although many data-driven MHD simulations have been developed and conducted, there are not many studies on how accurately those simulations can reproduce the phenomena observed in the solar corona. In this study, we investigated the performance of our data-driven simulation quantitatively using ground-truth data. The ground-truth data was produced by an MHD simulation in which the magnetic field is twisted by the sunspot motions. A magnetic flux rope (MFR) is created by the cancellation of the magnetic flux at the polarity inversion line due to the converging flow on the sunspot, which eventually leads to the eruption of the MFR. We attempted to reproduce these dynamics using the data-driven MHD simulation. The coronal magnetic fields are driven by the electric fields, which are obtained from a time series of the photospheric magnetic field that is extracted from the ground-truth data, on the surface. As a result, the data-driven simulation could capture the subsequent MHD processes, the twisted coronal magnetic field and formation of the MFR, and also its eruption. We report these results and compare them with the ground-truth data, and discuss how to improve the accuracy and optimize the numerical method.

Keywords: solar flares; magnetohydrodynamical simulations; solar active region magnetic fields; solar coronal mass ejections