adsabs/SciX_UAT_keywords huggingface dataset:
Adaptive Optics Imaging Can Break the Central Caustic Cusp Approach Degeneracy in High-magnification Microlensing Events

We report new results for the gravitational microlensing target OGLE-2011-BLG-0950 from adaptive optics images using the Keck Observatory. The original analysis by Choi et al. and reanalysis by Suzuki et al. report degenerate solutions between planetary and stellar binary lens systems. This particular case is the most important type of degeneracy for exoplanet demographics because the distinction between a planetary mass or stellar binary companion has direct consequences for microlensing exoplanet statistics. The 8 and 10 yr baselines allow us to directly measure a relative proper motion of 4.20 ± 0.21 mas yr-1, confirming the detection of the lens star system and ruling out the planetary companion models that predict a ~4× smaller relative proper motion. The Keck data also rule out the wide stellar binary solution unless one of the components is a stellar remnant. The combination of the lens brightness and close stellar binary light-curve parameters yields primary and secondary star masses of ${M}_{{\rm{A}}}={1.12}_{-0.09}^{+0.11}$ and ${M}_{{\rm{B}}}={0.47}_{-0.10}^{+0.13}\,{M}_{\odot }$ at a distance of ${D}_{L}={6.70}_{-0.30}^{+0.55}\,$ kpc and a projected separation of ${0.39}_{-0.04}^{+0.05}\,$ au. Assuming that the predicted proper motions are measurably different, the high-resolution imaging method described here can be used to disentangle this degeneracy for events observed by the Roman exoplanet microlensing survey using Roman images taken near the beginning or end of the survey.

Keywords: gravitational microlensing; binary lens microlensing; high-resolution microlensing event imaging; binary stars; galactic bulge
Multiwavelength Analysis and the C IV λ1549 Å Emission Line Behavior From 2008 to 2020 of FSRQ B2 1633+382

The flat-spectrum radio quasar B2 1633+382 (4C 38.41) has been monitored for several years and has presented correlated variability in multiple wavelengths. In this article, we are performing different analyses for multiple frequencies, from gamma rays to radio, as well as the C IV λ1549 Å emission line and the λ1350 Å continuum. Using the nonthermal dominance parameter, we separated the C IV and the continuum light curves for when the dominant source of continuum is the accretion disk or the jet. We found a correlation at a delay consistent with zero between the line and the continuum dominated by disk emission indicating a very small broad-line region (BLR). From the resulting delay between the 15 GHz and gamma rays, we estimated the distance of the gamma-ray emission region from the jet apex to be ~37 pc. The C IV flux decreases when the continuum and gamma rays increase at some of the high-activity periods. The C IV profile presents a larger variable component in its blue wing. The relation between the luminosities of C IV and the continuum does not completely follow the relation for a quasar sample. Our results lead us to propose an outflow of BLR material in the jet flow direction, a gamma-ray production through magnetic reconnection for the flaring event of mid-2011, and that there is not enough BLR material close to the radio core to be easily ionized by the nonthermal continuum.

Keywords: active galaxies; active galactic nuclei; galaxy jets; gamma-rays; emission line galaxies; quasars; flat-spectrum radio quasars; blazars; supermassive black holes
Hα Luminosity of ATLAS18qtd Does Not Plateau in the Nebular Phase

We present new spectroscopic and photometric observations of ATLAS18qtd/SN 2018cqj, a fast-declining SN Ia with variable Hα emission in previously published nebular phase spectra. ATLAS18qtd is undetected in both spectroscopic and photometric observations which occurred at ∼540 days after maximum light and ∼230 days after the last Hα detection. With these new non-detections, we place an upper limit on the Hα luminosity of $\lesssim 1.1\times {10}^{36}\,\mathrm{erg}\,{{\rm{s}}}^{-1}$ indicating the Hα flux decreased by a factor of $\gtrsim 4$ since the previous detection. This upper limit excludes Hα emission that plateaus or increases since the previous detection but cannot confirm that the Hα emission decay rate is equivalent to the supernova decay rate.

Keywords: type ia supernovae; circumstellar matter
Dynamics of Late-stage Reconnection in the 2017 September 10 Solar Flare

In this multi-instrument paper, we search for evidence of sustained magnetic reconnection far beyond the impulsive phase of the X8.2-class solar flare on 2017 September 10. Using Hinode/EIS, CoMP, SDO/AIA, K-Cor, Hinode/XRT, RHESSI, and IRIS, we study the late-stage evolution of the flare dynamics and topology, comparing signatures of reconnection with those expected from the standard solar flare model. Examining previously unpublished EIS data, we present the evolution of nonthermal velocity and temperature within the famous plasma sheet structure, for the first four hours of the flare's duration. On even longer timescales, we use differential emission measures and polarization data to study the longevity of the flare's plasma sheet and cusp structure, discovering that the plasma sheet is still visible in observations of CoMP linear polarization on 2017 September 11, long after its last appearance in EUV. We deduce that magnetic reconnection of some form is still ongoing at this time—27 hr after flare onset.

Keywords: solar flares; solar flare spectra; solar magnetic reconnection; spectropolarimetry; spectroscopy
Dynamical Friction in Nonlocal Gravity

We study dynamical friction in the Newtonian regime of nonlocal gravity (NLG), which is a classical nonlocal generalization of Einstein's theory of gravitation. The nonlocal aspect of NLG simulates dark matter. The attributes of the resulting effective dark matter are described and the main physical predictions of NLG, which has a characteristic length scale of order 1 kpc, for galactic dynamics are presented. Within the framework of NLG, we derive the analog of Chandrasekhar's formula for dynamical friction. The astrophysical implications of the results for the apparent rotation of a central bar subject to dynamical friction in a barred spiral galaxy are briefly discussed.

Keywords: gravitation; non-standard theories of gravity; barred spiral galaxies; dark matter
The Catalogue for Astrophysical Turbulence Simulations (CATS)

Turbulence is a key process in many fields of astrophysics. Advances in numerical simulations of fluids over the last several decades have revolutionized our understanding of turbulence and related processes such as star formation and cosmic ray propagation. However, data from numerical simulations of astrophysical turbulence are often not made public. We introduce a new simulation-oriented database for the astronomical community: the Catalogue for Astrophysical Turbulence Simulations (CATS), located at www.mhdturbulence.com. CATS includes magnetohydrodynamic (MHD) turbulent box simulation data products generated by the public codes ATHENA++, AREPO, ENZO> and FLASH. CATS also includes several synthetic observational data sets, such as turbulent HI data cubes. We also include measured power spectra and three-point correlation functions from some of these data. We discuss the importance of open-source statistical and visualization tools for the analysis of turbulence simulations such as those found in CATS.

Keywords: astronomy databases; magnetohydrodynamics; interstellar medium; interstellar dynamics
The Magnetic Origin of Solar Campfires

Solar campfires are fine-scale heating events, recently observed by Extreme Ultraviolet Imager (EUI) on board Solar Orbiter. Here we use EUI 174 Å images, together with EUV images from Solar Dynamics Observatory (SDO)/Atmospheric Imaging Assembly (AIA), and line-of-sight magnetograms from SDO/Helioseismic and Magnetic Imager (HMI) to investigate the magnetic origin of 52 randomly selected campfires in the quiet solar corona. We find that (i) the campfires are rooted at the edges of photospheric magnetic network lanes; (ii) most of the campfires reside above the neutral line between majority-polarity magnetic flux patch and a merging minority-polarity flux patch, with a flux cancelation rate of ~1018 Mx hr-1; (iii) some of the campfires occur repeatedly from the same neutral line; (iv) in the large majority of instances, campfires are preceded by a cool-plasma structure, analogous to minifilaments in coronal jets; and (v) although many campfires have "complex" structure, most campfires resemble small-scale jets, dots, or loops. Thus, "campfire" is a general term that includes different types of small-scale solar dynamic features. They contain sufficient magnetic energy (~1026-1027 erg) to heat the solar atmosphere locally to 0.5-2.5 MK. Their lifetimes range from about 1 minute to over 1 hr, with most of the campfires having a lifetime of <10 minutes. The average lengths and widths of the campfires are 5400 ± 2500 km and 1600 ± 640 km, respectively. Our observations suggest that (a) the presence of magnetic flux ropes may be ubiquitous in the solar atmosphere and not limited to coronal jets and larger-scale eruptions that make CMEs, and (b) magnetic flux cancelation is the fundamental process for the formation and triggering of most campfires.

Keywords: quiet sun; solar magnetic fields; solar coronal transients; solar filaments; solar coronal heating
Global Coronal Plasma Diagnostics Based on Multislit Extreme-ultraviolet Spectroscopy

Full-disk spectroscopic observations of the solar corona are highly desired to forecast solar eruptions and their impact on planets and to uncover the origin of solar wind. In this paper, we introduce a new multislit design (five slits) to obtain extreme-ultraviolet (EUV) spectra simultaneously. The selected spectrometer wavelength range (184–197 Å) contains several bright EUV lines that can be used for spectral diagnostics. The multislit approach offers an unprecedented way to efficiently obtain the global spectral data but the ambiguity from different slits should be resolved. Using a numerical simulation of the global corona, we primarily concentrate on the optimization of the disambiguation process, with the objective of extracting decomposed spectral information of six primary lines. This subsequently facilitates a comprehensive series of plasma diagnostics, including density (Fe XII 195.12/186.89 Å), Doppler velocity (Fe XII 193.51 Å), line width (Fe XII 193.51 Å), and temperature diagnostics (Fe VIII 185.21 Å, Fe X 184.54 Å, Fe XI 188.22 Å, and Fe XII 193.51 Å). We find a good agreement between the forward modeling parameters and the inverted results at the initial eruption stage of a coronal mass ejection, indicating the robustness of the decomposition method and its immense potential for global monitoring of the solar corona.

Keywords: solar atmosphere; solar extreme ultraviolet emission; solar instruments; spectroscopy; solar active regions
Projected Rotational Velocities for LAMOST Stars with Effective Temperatures Lower than 9000 K

In Data Release 9 of LAMOST, we present measurements of v sin i for a total of 121,698 stars measured using the Medium Resolution Spectrograph (MRS) and 80,108 stars using the Low Resolution Spectrograph (LRS). These values were obtained through a χ 2 minimization process, comparing LAMOST spectra with corresponding grids of synthetically broadened spectra. Due to the resolution and the spectral range of LAMOST, v sin i measurements are limited to stars with an effective temperature (T eff) ranging from 5000 to 8500 K for MRS and 7000 to 9000 K for LRS. The detectable v sin i for MRS is set between 27 and 350 km s‑1, and for LRS between 110 and 350 km s‑1. This limitation is because the convolved reference spectra become less informative beyond 350 km s‑1. The intrinsic precision of v sin i, determined from multiepoch observations, is approximately ∼4.0 km s‑1 for MRS and ∼10.0 km s‑1 for LRS at a signal-to-noise ratio greater than 50. Our v sin i values show consistency with those from APOGEE17, displaying a scatter of 8.79 km s‑1. They are also in agreement with measurements from the Gaia DR3 and Sun et al. catalogs. An observed trend in LAMOST MRS data is the decrease in v sin i with a drop in T eff, particularly transiting around 7000 K for dwarfs and 6500 K for giants, primarily observed in stars with near-solar abundances.

Keywords: astronomical techniques; stellar rotation
On the Measurement of Vorticity in Astrophysical Fluids

Vorticity is central to the nature of, and dynamical processes in turbulence, including turbulence in astrophysical fluids. The results of Raymond et al. on vorticity in the post-shock fluid of the Cygnus Loop supernova remnant are therefore of great interest. I consider the degree to which spectroscopic measurements of an optically thin line, the most common type of astronomical velocimetry, can yield unambiguous measurements of the vorticity in a fluid. I consider an ideal case of observations in the plane of a flow which possesses vorticity in a direction perpendicular to the plane of observations. The observationally deduced vorticity (referred to as the pseudovorticity) is a reasonable match for the true vorticity. However, the pseudovorticity of an irrotational model flow is also nonzero, and comparable in magnitude to that for a vortical flow. Astronomical spectroscopic observations may yield a good estimate of the vorticity, but its robustness cannot be insured.

Keywords: interstellar medium; interplanetary turbulence; plasma astrophysics
Radio Jet Feedback on the Inner Disk of Virgo Spiral Galaxy Messier 58

Spitzer spectral maps reveal a disk of highly luminous, warm (>150 K) H2 in the center of the massive spiral galaxy Messier 58, which hosts a radio-loud active galactic nucleus (AGN). The inner 2.6 kpc of the galaxy appears to be overrun by shocks from the radio jet cocoon. Gemini NIRI imaging of the H2 1–0 S(1) emission line, Atacama Large Millimeter/submillimeter Array CO 2–1, and Hubble Space Telescope multiband imagery indicate that much of the molecular gas is shocked in situ, corresponding to lanes of dusty molecular gas that spiral toward the galactic nucleus. The CO 2–1 and ionized gas kinematics are highly disturbed, with velocity dispersion up to 300 km s‑1. Dissipation of the associated kinetic energy and turbulence, likely injected into the interstellar medium by radio-jet-driven outflows, may power the observed molecular and ionized gas emission from the inner disk. The polycyclic aromatic hydrocarbon (PAH) fraction and composition in the inner disk appear to be normal, in spite of the jet and AGN activity. The PAH ratios are consistent with excitation by the interstellar radiation field from old stars in the bulge, with no contribution from star formation. The phenomenon of jet-shocked H2 may substantially reduce star formation and help to regulate the stellar mass of the inner disk and supermassive black hole in this otherwise normal spiral galaxy. Similarly strong H2 emission is found at the centers of several nearby spiral and lenticular galaxies with massive bulges and radio-loud AGNs.

Keywords: active galaxies; radio jets; shocks
WISE View of Changing-look Active Galactic Nuclei: Evidence for a Transitional Stage of AGNs

The discovery of changing-look active galactic nuclei (CLAGNs) with a significant change in optical broad emission lines (optical CLAGNs) and/or strong variation of line-of-sight column densities (X-ray CLAGNs) challenges the orientation-based AGN unification model. We explore mid-infrared (mid-IR) properties for a sample of 57 optical CLAGNs and 11 X-ray CLAGNs based on the Wide-field Infrared Survey Explorer archive data. We find that Eddington-scaled mid-IR luminosities of both optical and X-ray CLAGNs stay just between those of low-luminosity AGNs and luminous QSOs. The average Eddington-scaled mid-IR luminosities for optical and X-ray CLAGNs are ~0.4% and ~0.5%, respectively, which roughly correspond to the bolometric luminosity of transition between a radiatively inefficient accretion flow and a Shakura-Sunyaev disk. We estimate the time lags of the variation in the mid-IR behind that in the optical band for 13 CLAGNs with strong mid-IR variability, where the tight correlation between the time lag and the bolometric luminosity (τ-L) for CLAGNs roughly follows that found in the luminous QSOs.

Keywords: active galactic nuclei; seyfert galaxies; quasars; liner galaxies; reverberation mapping
Deep Learning of Dark Energy Spectroscopic Instrument Mock Spectra to Find Damped Lyα Systems

We have updated and applied a convolutional neural network (CNN) machine-learning model to discover and characterize damped Lyα systems (DLAs) based on Dark Energy Spectroscopic Instrument (DESI) mock spectra. We have optimized the training process and constructed a CNN model that yields a DLA classification accuracy above 99% for spectra that have signal-to-noise ratios (S/N) above 5 per pixel. The classification accuracy is the rate of correct classifications. This accuracy remains above 97% for lower S/N ≈1 spectra. This CNN model provides estimations for redshift and H I column density with standard deviations of 0.002 and 0.17 dex for spectra with S/N above 3 pixel-1. Also, this DLA finder is able to identify overlapping DLAs and sub-DLAs. Further, the impact of different DLA catalogs on the measurement of baryon acoustic oscillations (BAO) is investigated. The cosmological fitting parameter result for BAO has less than 0.61% difference compared to analysis of the mock results with perfect knowledge of DLAs. This difference is lower than the statistical error for the first year estimated from the mock spectra: above 1.7%. We also compared the performances of the CNN and Gaussian Process (GP) models. Our improved CNN model has moderately 14% higher purity and 7% higher completeness than an older version of the GP code, for S/N > 3. Both codes provide good DLA redshift estimates, but the GP produces a better column density estimate by 24% less standard deviation. A credible DLA catalog for the DESI main survey can be provided by combining these two algorithms.

Keywords: quasar absorption line spectroscopy; surveys; astronomy data analysis
Revisiting ϵ Eridani with NEID: Identifying New Activity-sensitive Lines in a Young K Dwarf Star

Recent improvements in the sensitivity and precision of the radial velocity (RV) method for exoplanets have brought it close, but not quite to, the threshold (~10 cm s-1) required to detect Earth-mass and other potentially habitable planets around Sun-like stars. Stellar activity-driven noise in RV measurements remains a significant hurdle to achieving this goal. While various efforts have been made to disentangle this noise from real planetary signals, a greater understanding of the relationship between spectra and stellar activity is crucial to informing stellar activity mitigation. We use a partially automated method to analyze spectral lines in a set of observations of the young, active star ϵ Eridani from the high-precision spectrograph NEID, correlate their features (depth, FWHM, and integrated flux) with known activity indicators, and filter and curate for well-defined lines whose shape changes are sensitive to certain types of stellar activity. We then present a list of nine lines correlated with the S-index in all three line features, including four newly identified activity-sensitive lines, as well as additional lines correlated with the S-index in at least one feature, and discuss the possible implications of the behavior observed in these lines. Our line lists represent a step forward in the empirical understanding of the complex relationships between stellar activity and spectra and illustrate the importance of studying the time evolution of line morphologies with stabilized spectrographs in the overall effort to mitigate activity in the search for small, potentially Earth-like exoplanets.

Keywords: stellar activity; spectral line lists; radial velocity; stellar spectral lines; exoplanet astronomy
Astrophysical Distance Scale. II. Application of the JAGB Method: A Nearby Galaxy Sample

We apply the near-infrared J-region asymptotic giant branch (JAGB) method, recently introduced by Madore & Freedman, to measure the distances to 14 nearby galaxies out to 4 Mpc. We use the geometric detached eclipsing binary (DEB) distances to the LMC and SMC as independent zero-point calibrators. We find excellent agreement with previously published distances based on the tip of the red giant branch (TRGB): the JAGB distance determinations (including the LMC and SMC) agree in the mean to within ${\rm{\Delta }}(\mathrm{JAGB}-\mathrm{TRGB})\,=+0.025\pm 0.013$ mag, just over 1%, where the TRGB I-band zero-point is MI = -4.05 mag. With further development and testing, the JAGB method has the potential to provide an independent calibration of Type Ia supernovae, especially with the James Webb Space Telescope. The JAGB stars (with MJ = -6.20 mag) can be detected farther than the fainter TRGB stars, allowing greater numbers of calibrating galaxies for the determination of H0. Along with the TRGB and Cepheids, JAGB stars are amenable to theoretical understanding and further refined empirical calibration. A preliminary test shows little dependence, if any, of the JAGB magnitude on metallicity of the parent galaxy. These early results suggest that the JAGB method has considerable promise for providing high-precision distances to galaxies in the local universe that are independent of distances derived from the Leavitt Law and/or the TRGB method, and it has numerous and demonstrable advantages over the possible use of Mira variables.

Keywords: distance indicators; galaxy distances; galactic and extragalactic astronomy; asymptotic giant branch stars; red giant branch
Intrinsic Emission of PSR B1937+21 at 327 MHz

At 327 MHz, the observed emission of PSR B1937+21 is greatly affected by scattering in the interstellar medium, on a timescale of order the pulse period. We use the bright impulsive giant pulses emitted by the pulsar to measure the impulse response of the interstellar medium and then recover the intrinsic emission of the pulsar by deconvolution—revealing fine structure on timescales not normally observable. We find that the intrinsic widths of the main pulse and interpulse in the pulse profile are similar to those measured at higher frequencies. We detect 60,270 giant pulses, which typically appear as narrow, ∼100 ns bursts consisting of one to a few nanoshots with widths ≲ 10 ns. However, about 10% of the giant pulses exhibit multiple bursts that seem to be causally related to each other. We also report the first detection of giant micropulses in PSR B1937+21, primarily associated with the regular main pulse emission. These are distinct from giant pulses not only in the phases at which they occur, but also in their larger widths, of order a microsecond, and steeper energy distribution. These measurements place useful observational constraints on emission mechanisms for giant pulses as well as the regular radio emission of millisecond pulsars.

Keywords: pulsars; radio bursts; deconvolution; millisecond pulsars