adsabs/SciX_UAT_keywords huggingface dataset:
Determining Subparsec Supermassive Black Hole Binary Orbits with Infrared Interferometry

Radial-velocity monitoring has revealed the presence of moving broad emission lines in some quasars, potentially indicating the presence of a subparsec binary system. Phase-referenced, near-infrared interferometric observations could map out the binary orbit by measuring the photocenter difference between a broad emission line and the hot dust continuum. We show that astrometric data over several years may be able to detect proper motions and accelerations, confirming the presence of a binary and constraining system parameters. The brightness, redshifts, and astrometric sizes of current candidates are well matched to the capabilities of the upgraded Very Large Telescope Interferometer/GRAVITY+ instrument, and we identify a first sample of 10 possible candidates. The astrometric signature depends on the morphology and evolution of hot dust emission in supermassive black hole binary systems. Measurements of the photocenter offset may reveal binary motion whether the hot dust emission region is fixed to the inner edge of the circumbinary disk, or moves in response to the changing irradiation pattern from an accreting secondary black hole.

Keywords: accretion; active galactic nuclei; supermassive black holes; interferometry
Extremely Relativistic Tidal Disruption Events

Extreme tidal disruption events (eTDEs), which occur when a star passes very close to a supermassive black hole, may provide a way to observe a long-sought general relativistic effect: orbits that wind several times around a black hole and then leave. Through general relativistic hydrodynamics simulations, we show that such eTDEs are easily distinguished from most tidal disruptions, in which stars come close, but not so close, to the black hole. Following the stellar orbit, the debris is initially distributed in a crescent, it then turns into a set of tight spirals circling the black hole, which merge into a shell expanding radially outwards. Some mass later falls back toward the black hole, while the remainder is ejected. Internal shocks within the infalling debris power the observed emission. The resulting lightcurve rises rapidly to roughly the Eddington luminosity, maintains this level for between a few weeks and a year (depending on both the stellar mass and the black hole mass), and then drops. Most of its power is in thermal X-rays at a temperature ~(1-2) × 106 K (~100-200 eV). The debris evolution and observational features of eTDEs are qualitatively different from ordinary TDEs, making eTDEs a new type of TDE. Although eTDEs are relatively rare for lower-mass black holes, most tidal disruptions around higher-mass black holes are extreme. Their detection offers a view of an exotic relativistic phenomenon previously inaccessible.

Keywords: tidal disruption; supermassive black holes; hydrodynamics; general relativity; gravitation
The Measurement of Masses of OB-type Stars from LAMOST DR5

The measurements of masses and luminosities of massive stars play an important role in understanding the formation and evolution of their host galaxies. In this work, we present the measurement of masses and luminosities of 2946 OB-type stars, including 78 O-type stars and 2868 B-type stars, based on their stellar parameters (effective temperature, surface gravity, and metallicity) and the Padova and Trieste Stellar Evolution Code isochrones model. Our results show that the median mass and luminosity of the 2946 OB-type stars are 5.4 M ⊙ and log(L/L ⊙) = 3.2 with median relative errors of 21.4% and 71.1%, respectively. A good agreement between our results estimated by using our method and those derived by using the orbital motions of binary stars from the literature is found for some B-type stars. In addition, we also fit the mass–luminosity relation of B-type stars by using our derived mass and the luminosity from Gaia Data Release 3.

Keywords: early-type stars
Observations of Outward-propagating and Mirroring of the Same Energetic Electrons by Wind

We report an energetic electron event observed by the Wind spacecraft in which electrons were first detected to propagate away from the Sun, and subsequently detected to propagate back toward the Sun. Using the recently developed fractional velocity dispersion analysis (FVDA), the path lengths corresponding to these two sequential electron signals were found to be ∼1.5 and ∼3.1 au. The inferred release times for both populations were found to be the same, within uncertainty. No bidirectional halo electrons were identified during the event, indicating that the electrons were not propagating within a closed magnetic field configuration (e.g., a magnetic flux rope). These observations suggest that the same energetic electrons were observed twice at 1 au, with the second time being due to reflection occurring beyond 1 au, by perhaps magnetic kinks caused by a coronal mass ejection-driven shock.

Keywords: solar energetic particles; interplanetary magnetic fields; solar coronal mass ejection shocks; solar coronal mass ejections
Quasi-periodic Dimming of the 130 Myr-old Debris-Disk Hosting Star HD 240779 is not Persistent

Quasi-periodic (1.5 days) dimming (by circumstellar dust) of the 135 Myr-old AB Doradus moving group member HD 240779 was detected in photometry by TESS in late 2018. Similar observations two years later show no such signal, and ground-based photometry indicate that the signal was absent in late 2019. This suggests that the source of the dust did not survive long after 2018, e.g., it was a disrupted planetesimal, or that dust production by the body is episodic, analogous to the "evaporating" planets detected by Kepler.

Keywords: planetesimals; debris disks; young stellar objects; circumstellar dust
Chemical Evolution History of MaNGA Galaxies

We show the results of a study using the spectral synthesis technique study for the full MaNGA sample showing their chemical enrichment history (ChEH) as well as the evolution of the stellar mass-metallicity relation (MZR) over cosmic time. We find that the more massive galaxies became enriched first and the lower-mass galaxies did so later, producing a change in the MZR that becomes shallower in time. Separating the sample into morphology and star-forming status bins, some particularly interesting results appear: The mass dependence of the MZR becomes less relevant for later morphological types, to the extent that it inverts for Sd/Irr galaxies, suggesting that morphology is at least as important a factor as mass in the chemical evolution. The MZR for the full sample shows a flattening at the high-mass end and another in the low-mass range, but the former only appears for retired galaxies, while the latter only appears for star-forming galaxies. We also find that the average metallicity gradient is currently negative for all mass bins, but for low-mass galaxies, it was inverted at some point in the past, before which all galaxies had a positive gradient. We also compare how diverse the ChEHs are in the different bins we considered, as well as what primarily drives the diversity: By how much galaxies become enriched, or how quickly they do so.

Keywords: galaxies; chemical abundances; galaxy chemical evolution
GCM-motivated Multidimensional Temperature Parametrization Scheme for Phase-curve Retrieval

We present a novel physically motivated, parametrized temperature model for phase-curve retrieval, able to self-consistently assess the variation in thermal structure in multidimensions. To develop this approach, we drew motivation from both full three-dimensional general circulation models and analytic formulations, accounting for the dominant dynamical feature of tidally locked planets, the planetary jet. Our formulation shows notable flexibility. It can generate planetary jets of various characteristics and redistribution efficiencies seen in the literature, including both standard eastward and unusual westward offset hotspots, as well as more exotic configurations for potential future observations. In our modeling scheme we utilize a tractable set of parameters efficient enough to enable future Bayesian analysis and, in addition to the resolved temperature structure, we return physical insights not yet derived from retrievals: the amplitude and the phase offset, and the location and the extent of the equatorial jet.

Keywords: exoplanet atmospheres; exoplanet structure
Periodically Modulated Magnetic Reconnection

We present the first evidence for periodically modulated reconnection at the electron scale in space, using unparalleled, high-cadence data from Magnetospheric Multiscale spacecraft. The periodic modulation is attributed to finite magnetic trapping imposed by the X-line, which generates discrete, dispersive electron stripes. The dispersive stripes, well reproduced by a trapping-loss transition model, periodically break the frozen-in condition and drive energy dissipation. Such an electron transition effect eliminates free electrons, enhances electron mixing, and causes highly structured, three-dimensional distributions that generate intense radio emissions. These illuminating results, suggesting that reconnection hosts inherent periodicity determined by three-dimensional electron physics, provide crucial insights into understanding reconnection-driven energy transport in space and astrophysical plasmas.

Keywords: space plasmas
A Novel Survey for Young Substellar Objects with the W-band Filter. II. The Coolest and Lowest Mass Members of the Serpens-South Star-forming Region

Given its relative proximity (∼430 pc), compact size (<20'), young age (∼0.5 Myr), and rich number of young stellar objects, the Serpens-South star-forming region is a promising site for studying young substellar objects, yet the low-mass members of this region remain largely undiscovered. In this article we report on a deep photometric survey using a custom 1.45 μm filter (W band), as well as standard J and H near-IR filters, in order to identify candidate low-mass young brown dwarfs in the Serpens-South region. We constructed a reddening-insensitive index (Q) by combining J, H and W-band photometry for survey objects, in order to identify candidate low-mass members of Serpens based on the strength of the water-absorption feature at 1.45 μm in the atmospheres of mid-M and later objects. We then conducted spectroscopic follow-up to confirm youth and spectral type for our candidates. This is the first survey to identify the very low-mass and coolest members of Serpens-South. We identify four low-mass candidate Serpens members, which all display IR excess emission, indicating the likely presence of circumstellar disks around them. One of the four candidate low-mass members in our list, SERP182918-020245, exhibits Paβ and Brγ emission features, confirming its youth and ongoing magnetospheric accretion. Our new candidate members have spectral types >M4 and are the coolest and lowest mass candidate members yet identified in Serpens-South.

Keywords: brown dwarfs; low mass stars; m subdwarf stars; pre-main sequence stars; young stellar objects; infrared excess
Pressure Balance and Energy Budget of the Nuclear Superbubble of NGC 3079

Superbubbles in the nuclear region of galaxies could be produced by active galactic nuclei (AGN) or nuclear starburst via different driving forces. We report analysis of the multiwavelength data of the kiloparsec-scale nuclear superbubble in NGC 3079 in order to probe the mechanisms driving the expansion of the superbubble. Based on the Chandra X-ray observations, we derive the hot-gas thermal pressure inside the bubble, which is about 1 order of magnitude higher than that of the warm ionized gas traced by optical lines. We derive a [C II]-based star formation rate (SFR) of SFR ∼ 1.3 M ⊙ yr‑1 from the nuclear region using the SOFIA/FIFI-LS observation. This SFR infers a radiation pressure toward the bubble shells much lower than the thermal pressure of the gases. The Very Large Array radio image infers that magnetic pressure at the northeast cap above the superbubble is less than the thermal pressure of the hot gas enclosed in the bubble but has a clearly larger extension. The magnetic field may thus still help to reconcile the expansion of the bubble. The observed thermal energy of the hot gas enclosed in the bubble requires an energy injection rate of ≳1042 erg s‑1 within the bubble's dynamical age, which is probably larger than the power provided by the current nuclear starburst and the parsec-scale jet. If this is true, stronger past AGN activity may provide an alternative energy source to drive the observed bubble expansion.

Keywords: superbubbles; cosmic rays; active galaxies; starburst galaxies
Automatic Échelle Spectrograph Wavelength Calibration

Time-domain astronomy and the increasing number of exoplanet candidates call for reliable, robust, and automatic wavelength calibration. We present an algorithm for wavelength-calibrating échelle spectrographs that uses order-by-order extracted spectra and a list of laboratory wavelengths. Our approach is fully automatic and does not need the pixel locations of certain spectral features with which to anchor the wavelength solution, nor the true order number of each diffraction order. We use spectral features that are duplicated in adjacent orders to establish the scale-invariant component of the wavelength solution. We then match the central wavelengths of spectral features to laboratory wavelengths to establish the scale and higher-order components of the wavelength solution. We demonstrate our method on the four spectrographs of Las Cumbres Observatory's Network of Robotic Échelle Spectrographs (NRES), on the High Accuracy Radial Velocity Planet Searcher (HARPS) spectrograph, and on synthetic data. We obtain a velocity-equivalent precision of ∼10 m s-1 on NRES. We achieve ∼1 m s-1 on HARPS, which agrees with the precision reported by the HARPS team. On synthetic data, we achieve the velocity precision set by Gaussian centroiding errors. Our algorithm likely holds for a wide range of spectrographs beyond the five presented here. We provide an open-source Python package, xwavecal, which outputs wavelength-calibrated spectra as well as the wavelengths of spectral features.

Keywords: exoplanet detection methods; open source software; astronomical instrumentation; radial velocity; high resolution spectroscopy; astronomy software
Jupiter's Banding and Jets May Be Caused by Tides

The stratification parameters for Jupiter's outer 3000 km shell are calculated using a density profile recently derived from observations of the NASA Juno spacecraft currently in Jovian orbit. Using these parameters, the equations of classical tidal theory for a stratified, nonhydrostatic, compressible fluid are numerically solved for sectoral tidal forcing by Io. The results support a long-standing though little discussed proposal that the banding/jets (and possibly the unexplained endogenic heat) are caused by the tides. First, general arguments from eigenmode analyses expect resonantly forced tidal modes and the scattering of the tidal response to higher spatial degrees by Jupiter's fast rotation, with time-averaged tidal effects appearing in bands between critical latitudes (±50° for forcing by Io). Second, resonant tides and banding are specifically demonstrated in the tidal model configured with the Juno-derived stratification. While banding in the time-averaged tidal features is a robust expectation (from the well-prescribed forcing and rotation parameters) and is independent of the internal parameters, the details of the banding (e.g., number, width) are highly dependent. Hence, comparison of the tidal model with observations provides a test of the tidal hypothesis of the bands as well as assumptions of interior parameters and processes. Here, dissipation parameterized as a simple pressure relaxation term in the vertical balance equation shows a time-mean banded structure between the critical latitudes that can drive geostrophic jets matching the major observed features, including strong prograde flow at the equator. By contrast, alternate stratification/dissipation assumptions produce banded structures that do not agree with observations.

Keywords: jupiter; hot jupiters; solar system gas giant planets; atmospheric tides; tides
Supervised Machine Learning for Intercomparison of Model Grids of Brown Dwarfs: Application to GJ 570D and the Epsilon Indi B Binary System

Self-consistent model grids of brown dwarfs involve complex physics and chemistry, and are often computed using proprietary computer codes, making it challenging to identify the reasons for discrepancies between model and data as well as between the models produced by different research groups. In the current study, we demonstrate a novel method for analyzing brown dwarf spectra, which combines the use of the Sonora, AMES-cond, and HELIOS model grids with the supervised machine-learning method of the random forest. Besides performing atmospheric retrieval, the random forest enables information content analysis of the three model grids as a natural outcome of the method, both individually on each grid and by comparing the grids against one another, by computing large suites of mock retrievals. Our analysis reveals that the different choices made in modeling the alkali line shapes hinder the use of the alkali lines as gravity indicators. Nevertheless, the spectrum longward of 1.2 μm encodes enough information on the surface gravity to allow its inference from retrieval. Temperature may be accurately and precisely inferred independent of the choice of model grid, but not the surface gravity. We apply random forest retrieval to three objects: the benchmark T7.5 brown dwarf GJ 570D, and ɛ Indi Ba (T1.5 brown dwarf) and Bb (T6 brown dwarf), which are part of a binary system and have measured dynamical masses. For GJ 570D, the inferred effective temperature and surface gravity are consistent with previous studies. For ɛ Indi Ba and Bb, the inferred surface gravities are broadly consistent with the values informed by the dynamical masses.

Keywords: brown dwarfs; t dwarfs; astrostatistics techniques
The Width of Magnetic Ejecta Measured near 1 au: Lessons from STEREO-A Measurements in 2021–2022

Coronal mass ejections (CMEs) are large-scale eruptions with a typical radial size at 1 au of 0.21 au but their angular width in interplanetary space is still mostly unknown, especially for the magnetic ejecta (ME) part of the CME. We take advantage of STEREO-A angular separation of 20°–60° from the Sun–Earth line from 2020 October to 2022 August, and perform a two-part study to constrain the angular width of MEs in the ecliptic plane: (a) we study all CMEs that are observed remotely to propagate between the Sun–STEREO-A and the Sun–Earth lines and determine how many impact one or both spacecraft in situ, and (b) we investigate all in situ measurements at STEREO-A or at L1 of CMEs during the same time period to quantify how many are measured by the two spacecraft. A key finding is that out of 21 CMEs propagating within 30° of either spacecraft only four impacted both spacecraft and none provided clean magnetic cloud-like signatures at both spacecraft. Combining the two approaches, we conclude that the typical angular width of an ME at 1 au is ∼20°–30°, or 2–3 times less than often assumed and consistent with a 2:1 elliptical cross section of an ellipsoidal ME. We discuss the consequences of this finding for future multi-spacecraft mission designs and for the coherence of CMEs.

Keywords: solar coronal mass ejections; ejecta; interplanetary physics
ReveaLLAGN 0: First Look at JWST MIRI Data of Sombrero and NGC 1052

We present the first results from the Revealing Low-Luminosity Active Galactic Nuclei (ReveaLLAGN) survey, a JWST survey of seven nearby LLAGNs. We focus on two observations with the Mid-Infrared Instrument (MIRI)'s Medium-Resolution Spectrometer of the nuclei of NGC 1052 and Sombrero (NGC 4594/M104). We also compare these data to public JWST data of higher-luminosity AGNs, NGC 7319 and NGC 7469. JWST clearly separates the AGN spectrum from the galaxy light even in Sombrero, the faintest target in our survey; the AGN components have very red spectra. We find that the emission-line widths in both NGC 1052 and Sombrero increase with increasing ionization potential, with FWHM > 1000 km s‑1 for lines with ionization potential ≳ 50 eV. These lines are also significantly blueshifted in both LLAGNs. The high-ionization-potential lines in NGC 7319 show neither broad widths nor significant blueshifts. Many of the lower-ionization-potential emission lines in Sombrero show significant blue wings extending >1000 km s‑1. These features and the emission-line maps in both galaxies are consistent with outflows along the jet direction. Sombrero has the lowest-luminosity high-ionization-potential lines ([Ne V] and [O IV]) ever measured in the mid-infrared, but the relative strengths of these lines are consistent with higher-luminosity AGNs. On the other hand, the [Ne V] emission is much weaker relative to the [Ne III] and [Ne II] lines of higher-luminosity AGNs. These initial results show the great promise that JWST holds for identifying and studying the physical nature of LLAGNs.

Keywords: active galactic nuclei; low-luminosity active galactic nuclei; james webb space telescope; infrared spectroscopy; liner galaxies
The GBT Diffuse Ionized Gas Survey: Tracing the Diffuse Ionized Gas around the Giant Hii Region W43

The Green Bank Telescope Diffuse Ionized Gas Survey (GDIGS) is a fully sampled radio recombination line (RRL) survey of the inner Galaxy at C-band (4-8 GHz). We average together ∼15 Hnα RRLs within the receiver bandpass to improve the spectral signal-to-noise ratio. The average beam size for the RRL observations at these frequencies is ∼2'. We grid these data to have spatial and velocity spacings of 30″ and 0.5 $\mathrm{km}\,{{\rm{s}}}^{-1}$ , respectively. Here we discuss the first RRL data from GDIGS: a 6 deg2 area surrounding the Galactic H II region complex W43. We attempt to create a map devoid of emission from discrete H II regions and detect RRL emission from the diffuse ionized gas (DIG) across nearly the entire mapped area. We estimate the intensity of the DIG emission by a simple empirical model, taking only the H II region locations, angular sizes, and RRL intensities into account. The DIG emission is predominantly found at two distinct velocities: ∼40 and ∼100 $\mathrm{km}\,{{\rm{s}}}^{-1}$ . While the 100 $\mathrm{km}\,{{\rm{s}}}^{-1}$ component is associated with W43 at a distance of ∼6 kpc, the origin of the 40 $\mathrm{km}\,{{\rm{s}}}^{-1}$ component is less clear. Since the distribution of the 40 $\mathrm{km}\,{{\rm{s}}}^{-1}$ emission cannot be adequately explained by ionizing sources at the same velocity, we hypothesize that the plasma at the two velocity components is interacting, placing the 40 $\mathrm{km}\,{{\rm{s}}}^{-1}$ DIG at a similar distance as the 100 $\mathrm{km}\,{{\rm{s}}}^{-1}$ emission. We find a correlation between dust temperature and integrated RRL intensity, suggesting that the same radiation field that heats the dust also maintains the ionization of the DIG.

Keywords: interstellar medium; galactic radio sources; radio astronomy; interstellar abundances; h ii regions; warm ionized medium; surveys; photodissociation regions