adsabs/SciX_UAT_keywords huggingface dataset:
An Eclipsing Black Widow Pulsar in NGC 6712

We report the discovery of the first radio pulsar associated with NGC 6712, an eclipsing black widow (BW) pulsar, J1853-0842A, found by high-sensitivity searches using the Five-hundred-meter Aperture Spherical radio Telescope. This 2.15 ms pulsar is in a 3.56 hr compact circular orbit with a very low mass companion likely of mass 0.018 to 0.036 M⊙ and exhibits eclipsing of the pulsar signal. Though the distance to PSR J1853-0842A predicted from its dispersion measure (155.125 ± 0.004 cm-3 pc) and Galactic free electron density models are about 30% smaller than that of NGC 6712 obtained from interstellar reddening measurements, this is likely due to limited knowledge about the spiral arms and Scutum stellar cloud in this direction. Follow-up timing observations spanning 445 days allow us to localize the pulsar's position to be 0.14 core radii from the center of NGC 6712 and measure a negative spin-down rate for this pulsar of -2.39(2) × 10-21 s s-1. The latter cannot be explained without the acceleration of the globular cluster (GC) and decisively supports the association between PSR J1853-0842A and NGC 6712. Considering the maximum GC acceleration, the Galactic acceleration, and the Shklovskii effect, we place an upper limit on the intrinsic spin-down rate to be 1.11 × 10-20 s s-1. From an analysis of the eclipsing observations, we estimate the electron density of the eclipse region to be about 1.88 × 106 cm-3. We also place an upper limit of the accretion rate from the companion at about 3.05 × 10-13 M⊙ yr-1, which is comparable with some other BWs.

Keywords: pulsars
A Low-mass, Pre-main-sequence Eclipsing Binary in the 40 Myr Columba Association-Fundamental Stellar Parameters and Modeling the Effect of Star Spots

Young eclipsing binaries (EBs) are powerful probes of early stellar evolution. Current models are unable to simultaneously reproduce the measured and derived properties that are accessible for EB systems (e.g., mass, radius, temperature, and luminosity). In this study we add a benchmark EB to the pre-main-sequence population with our characterization of TOI 450 (TIC 77951245). Using Gaia astrometry to identify its comoving, coeval companions, we confirm TOI 450 is a member of the ~40 Myr Columba association. This eccentric (e = 0.2969), equal-mass (q = 1.000) system provides only one grazing eclipse. Despite this, our analysis achieves the precision of a double-eclipsing system by leveraging information in our high-resolution spectra to place priors on the surface-brightness and radius ratios. We also introduce a framework to include the effect of star spots on the observed eclipse depths. Multicolor eclipse light curves play a critical role in breaking degeneracies between the effects of star spots and limb-darkening. Including star spots reduces the derived radii by ~2% from a unspotted model (>2σ) and inflates the formal uncertainty in accordance with our lack of knowledge regarding the starspot orientation. We derive masses of 0.1768( ± 0.0004) and 0.1767( ± 0.0003) M ⊙, and radii of 0.345(±0.006) and 0.346(±0.006) R ⊙ for the primary and secondary, respectively. We compare these measurements to multiple stellar evolution isochones, finding good agreement with the association age. The MESA MIST and SPOTS (f s = 0.17) isochrones perform the best across our comparisons, but detailed agreement depends heavily on the quantities being compared.

Keywords: m stars; eclipsing binary stars; starspots; pre-main sequence stars
Three-dimensional Dissipative Pulsar Magnetospheres with Aristotelian Electrodynamics

A good compromise between the resistive model and the particle-in-cell model is Aristotelian electrodynamics, which can include the back-reaction of the radiative photons onto particle motion and allow for a local dissipation where the force-free condition is violated. We study the dissipative pulsar magnetosphere with Aristotelian electrodynamics where particle acceleration is fully balanced by radiation. The expression for the current density is defined by introducing a pair multiplicity. The 3D structure of the pulsar magnetosphere is then presented by solving the time-dependent Maxwell equations using a pseudo-spectral algorithm. It is found that the dissipative magnetosphere approaches the force-free solution and the dissipative region is more restricted to the current sheet outside the light cylinder (LC) as the pair multiplicity increases. The spatial extension of the dissipative region is self-consistently controlled by the pair multiplicity. Our simulations show the high magnetospheric dissipation outside the LC for the low pair multiplicity.

Keywords: pulsars; magnetohydrodynamical simulations; magnetic fields
[C II] Spectral Mapping of the Galactic Wind and Starbursting Disk of M82 with SOFIA

M82 is an archetypal starburst galaxy in the local Universe. The central burst of star formation, thought to be triggered by M82's interaction with other members in the M81 group, is driving a multiphase galaxy-scale wind away from the plane of the disk that has been studied across the electromagnetic spectrum. Here, we present new velocity-resolved observations of the [C II] 158 μm line in the central disk and the southern outflow of M82 using the upGREAT instrument on board SOFIA. We also report the first detections of velocity-resolved (ΔV = 10 km s-1) [C II] emission in the outflow of M82 at projected distances of ≈1-2 kpc south of the galaxy center. We compare the [C II] line profiles to observations of CO and H I and find that likely the majority (>55%) of the [C II] emission in the outflow is associated with the neutral atomic medium. We find that the fraction of [C II] actually outflowing from M82 is small compared to the bulk gas outside the midplane (which may be in a halo or tidal streamers), which has important implications for observations of [C II] outflows at higher redshift. Finally, by comparing the observed ratio of the [C II] and CO intensities to models of photodissociation regions, we estimate that the far-ultraviolet (FUV) radiation field in the disk is ~103.5 G 0, in agreement with previous estimates. In the outflow, however, the FUV radiation field is 2-3 orders of magnitudes lower, which may explain the high fraction of [C II] arising from the neutral medium in the wind.

Keywords: starburst galaxies; galaxy winds; interstellar medium; galaxy kinematics; molecular gas; interstellar atomic gas; far infrared astronomy; infrared galaxies
Compact-object Formation, Retention, and Growth through Accretion onto Gas-embedded White Dwarfs/Neutron Stars in Gas-enriched Globular Clusters

Observations of pulsars in globular clusters (GCs) give evidence that more than >10%-20% of neutron stars (NSs) that ever formed in GCs were retained there. However, the velocity distribution of field pulsars peaks at 5-10 times the escape velocities of GCs. Consequently, only a small fraction of GC NSs should have been retained, which is potentially difficult to explain even accounting for low-velocity NSs formed through electron-capture supernovae (SNe). Thus, too few low-velocity NSs should have been retained, giving rise to the NS retention problem in GCs. Here we suggest a novel solution, in which the progenitors of most GC NSs were ONe white dwarfs (WDs) that accreted ambient intracluster gas and formed low-velocity NSs through accretion-induced collapse (AIC). The existence of an early gas-enriched environment in GCs is supported by observations of multiple stellar populations in GCs. It is thought that 10-100s of megayears after the formation of the first generation of stars, and after ONe WDs were already formed, GCs were replenished with gas, which formed a second generation of stars. Accretion of such replenished gas onto the ONe WDs catalyzed the AIC processes. The number of AIC-formed NSs is then sufficient to explain the large number of NSs retained in GCs. Similar processes might also drive CO WDs to produce Type Ia SNe or to merge and form NSs and similarly drive NSs to AIC and mergers producing BHs. Moreover, the wide variety of gas-catalyzed binary mergers and explosive transients suggested to occur in the gas-rich environments of an active galactic nucleus disk could similarly, and even more efficiently, occur in second-generation gas in GCs.

Keywords: globular star clusters; neutron stars; white dwarf stars; stellar mass black holes; bondi accretion; novae; young massive clusters
Second Data Release of the All-sky NOIRLab Source Catalog

We announce the second data release (DR2) of the NOIRLab Source Catalog (NSC), using 412,116 public images from CTIO-4 m+DECam, the KPNO-4 m+Mosaic3, and the Bok-2.3 m+90Prime. NSC DR2 contains over 3.9 billion unique objects, 68 billion individual source measurements, covers ≈35,000 square degrees of the sky, has depths of ≈23 mag in most broadband filters with ≈1%-2% photometric precision, and astrometric accuracy of ≈7 mas. Approximately 1.9 billion objects within ≈30,000 square degrees of sky have photometry in three or more bands. There are several improvements over NSC DR1. DR2 includes 156,662 (61%) more exposures extending over 2 more years than in DR1. The southern photometric zero-points in griz are more accurate by using the Skymapper DR1 and ATLAS-Ref2 catalogs, and improved extinction corrections were used for high-extinction regions. In addition, the astrometric accuracy is improved by taking advantage of Gaia DR2 proper motions when calibrating the astrometry of individual images. This improves the NSC proper motions to ∼2.5 mas yr-1 (precision) and ∼0.2 mas yr-1 (accuracy). The combination of sources into unique objects is performed using a DBSCAN algorithm and mean parameters per object (such as mean magnitudes, proper motion, etc.) are calculated more robustly with outlier rejection. Finally, eight multi-band photometric variability indices are calculated for each object and variable objects are flagged (23 million objects). NSC DR2 will be useful for exploring solar system objects, stellar streams, dwarf satellite galaxies, quasi-stellar objects, variable stars, high proper-motion stars, and transients. Several examples of these science use cases are presented. The NSC DR2 catalog is publicly available via the NOIRLab's Astro Data Lab science platform.

Keywords: surveys; catalogs; solar system astronomy; variable stars; proper motions
Panchromatic Photometry of Low-redshift, Massive Galaxies Selected from SDSS Stripe 82

The broadband spectral energy distribution of a galaxy encodes valuable information on its stellar mass, star formation rate (SFR), dust content, and possible fractional energy contribution from nonstellar sources. We present a comprehensive catalog of panchromatic photometry, covering 17 bands from the far-ultraviolet to 500 μm, for 2685 low-redshift (z = 0.01-0.11), massive (M * > 1010 M ⊙) galaxies selected from the Stripe 82 region of the Sloan Digital Sky Survey, one of the largest areas with relatively deep, uniform observations over a wide range of wavelengths. Taking advantage of the deep optical coadded images, we develop a hybrid approach for matched-aperture photometry of the multiband data. We derive robust uncertainties and upper limits for undetected galaxies, deblend interacting/merging galaxies and sources in crowded regions, and treat contamination by foreground stars. We perform spectral energy distribution fitting to derive the stellar mass, SFR, and dust mass, critically assessing the influence of flux upper limits for undetected photometric bands and applying corrections for systematic uncertainties based on extensive mock tests. Comparison of our measurements with those of commonly used published catalogs reveals good agreement for the stellar masses. While the SFRs of galaxies on the star-forming main sequence show reasonable consistency, galaxies in and below the green valley show considerable disagreement between different sets of measurements. Our analysis suggests that one should incorporate the most accurate and inclusive photometry into the spectral energy distribution analysis, and that care should be exercised in interpreting the SFRs of galaxies with moderate to weak star formation activity.

Keywords: active galaxies; galaxy evolution; infrared galaxies; surveys
Determining Dust Properties in Protoplanetary Disks: SED-derived Masses and Settling with ALMA

We present spectral energy distribution (SED) modeling of 338 disks around T Tauri stars from 11 star-forming regions, ranging from ~0.5 to 10 Myr old. The disk masses we infer from our SED models are typically greater than those reported from (sub)millimeter surveys by a factor of 1.5-5, with the discrepancy being generally higher for the more massive disks. Masses derived from (sub)millimeter fluxes rely on the assumption that the disks are optically thin at all millimeter wavelengths, which may cause the disk masses to be underestimated since the observed flux is not sensitive to the whole mass in the disk; SED models do not make this assumption and thus yield higher masses. Disks with more absorbing material should be optically thicker at a given wavelength, which could lead to a larger discrepancy for disks around massive stars when the disk temperature is scaled by the stellar luminosity. We also compare the disk masses and degree of dust settling across the different star-forming regions and find that disks in younger regions are more massive than disks in older regions, but with a similar degree of dust settling. Together, these results offer potential partial solutions to the "missing" mass problem: disks around T Tauri stars may indeed have enough material to form planetary systems, though previous studies have underestimated the mass by assuming the disks to be optically thin; these planetary systems may also form earlier than previously theorized since significant dust evolution (i.e., settling) is already apparent in young disks.

Keywords: t tauri stars; exoplanet formation; protoplanetary disks; star formation
Evidence for Returning Disk Radiation in the Black Hole X-Ray Binary XTE J1550-564

We explore the accretion properties of the black hole X-ray binary XTE J1550-564 during its outbursts in 1998/99 and 2000. We model the disk, corona, and reflection components of X-ray spectra taken with the Rossi X-ray Timing Explorer, using the relxill suite of reflection models. The key result of our modeling is that the reflection spectrum in the very soft state is best explained by disk self-irradiation, I.e., photons from the inner disk are bent by the strong gravity of the black hole and reflected off the disk surface. This is the first known detection of thermal disk radiation reflecting off the inner disk. There is also an apparent absorption line at ∼6.9 keV, which may be evidence of an ionized disk wind. The coronal electron temperature (kTe) is, as expected, lower in the brighter outburst of 1998/99, explained qualitatively by more efficient coronal cooling due to irradiating disk photons. The disk inner radius is consistent with being within a few times the innermost stable circular orbit throughout the bright-hard-to-soft states (10 s of rg in gravitational units). The disk inclination is low during the hard state, disagreeing with the binary inclination value, and very close to 90° in the soft state, recovering to a lower value when adopting a blackbody spectrum as the irradiating continuum.

Keywords: accretion; astrophysical black holes; black hole physics; kerr black holes; atomic physics; low-mass x-ray binary stars
Deep Follow-up for Gravitational-wave Inference: A Case Study with GW151226

New analyses of gravitational-wave events raise questions about the nature of some events. For example, LIGO-Virgo-KAGRA initially determined GW151226 to be a merger with a mass ratio q ≈ 0.5 and effective inspiral spin χ eff ≈ 0.2. However, recent works offer an alternative picture: GW151226 is a lower mass ratio event q ≈ 0.3 with slightly higher spin χ eff ≈ 0.3. This discrepancy has been challenging to resolve, as a wide range of differences are employed for each analysis. This work introduces a "deep follow-up" framework to efficiently compute the posterior odds between two different peaks in parameter space. In doing so, we aim to help resolve disputes about the true nature of gravitational-wave events associated with conflicting astrophysical interpretations. Our proposal is not a replacement for standard inference techniques; instead, our method provides a diagnostic tool to understand discrepancies between conflicting results. We demonstrate this method by studying three q-χ eff peaks proposed for GW151226. We find that the (q ~ 0.5, χ eff ~ 0.2) interpretation is only slightly preferred over the (q ~ 0.3, χ eff ~ 0.3) hypothesis with posterior odds of ~1.7 ± 0.4, suggesting that neither of the two peaks can be ruled out. We discuss strategies to produce more reliable parameter estimation studies in gravitational-wave astronomy.

Keywords: black holes; gravitational waves; gravitational wave astronomy; astronomical methods; bayesian statistics; ligo
A Search for Temporal Atmospheric Variability of Kepler Hot Jupiters

We perform a systematic search for atmospheric variability in short-period gas-giant planets (hot Jupiters) observed by the Kepler mission, by looking for temporal variability of their secondary eclipse depths. This is motivated by a recent detection of a decrease in the dayside brightness of KELT-1 b between TESS Sectors 17 and 57, separated by about 3 yr. We fit the Kepler light curves of 53 hot Jupiters and measure their secondary eclipse depths during individual Kepler quarters and four-quarter windows. We detect the secondary eclipses in individual quarters or four-quarter windows for 17 out of the 53 systems. In those 17 systems we do not detect statistically significant astrophysical variation in the secondary eclipse depths. We show that the data is sensitive to the variability seen for KELT-1 b in TESS data. Therefore, the absence of detected secondary eclipse variability in Kepler data suggests that the atmospheric variability in KELT-1 b is not common. In addition, several of the 53 targets we investigated display variability in their transit depths with a period of four quarters (1 yr). This instrumental signal is likely present in the light curves of other transiting planets we did not analyze and other variable stars observed by Kepler. Finally, we find that Kepler-488 b has a secondary eclipse depth that is unphysically large for a planet, and thus is likely a misclassified red dwarf.

Keywords: hot jupiters; exoplanets; exoplanet atmospheric variability
A Tale of Two Circularization Periods

We reanalyze the exquisite eclipsing binary data from the Kepler and TESS missions, focusing on eccentricity measurements at short orbital periods to empirically constrain tidal circularization. We calculate a circularization period of ~6 days due to nearly circular binaries with long orbital periods ("cold core") but find many binaries with moderate eccentricities that circularize interior to only ~3 days ("eccentricity envelope"). We show that these features are present in previous spectroscopic surveys. We also reaffirm the statistically significant difference between the eccentricity distributions of young (<1 Gyr) and old (>3 Gyr) binaries. Our work introduces new methods that have the potential to reconcile theoretical predictions with observations to empirically constrain tidal circularization.

Keywords: close binary stars; eclipsing binary stars; tides; binary stars
Periodic Radio Emission from the T8 Dwarf WISE J062309.94-045624.6

We present the detection of rotationally modulated, circularly polarized radio emission from the T8 brown dwarf WISE J062309.94-045624.6 between 0.9 and 2.0 GHz. We detected this high-proper-motion ultracool dwarf with the Australian SKA Pathfinder in 1.36 GHz imaging data from the Rapid ASKAP Continuum Survey. We observed WISE J062309.94-045624.6 to have a time and frequency averaged Stokes I flux density of 4.17 ± 0.41 mJy beam-1, with an absolute circular polarization fraction of 66.3% ± 9.0%, and calculated a specific radio luminosity of L ν ~ 1014.8 erg s-1 Hz-1. In follow-up observations with the Australian Telescope Compact Array and MeerKAT we identified a multipeaked pulse structure, used dynamic spectra to place a lower limit of B > 0.71 kG on the dwarf's magnetic field, and measured a P = 1.912 ± 0.005 hr periodicity, which we concluded to be due to rotational modulation. The luminosity and period we measured are comparable to those of other ultracool dwarfs observed at radio wavelengths. This implies that future megahertz to gigahertz surveys, with increased cadence and improved sensitivity, are likely to detect similar or later-type dwarfs. Our detection of WISE J062309.94-045624.6 makes this dwarf the coolest and latest-type star observed to produce radio emission.

Keywords: t dwarfs; brown dwarfs; radio astronomy; magnetospheric radio emissions
Element Stratification in the Middle-aged SN Ia Remnant G344.7-0.1

Despite their importance, a detailed understanding of Type Ia supernovae (SNe Ia) remains elusive. X-ray measurements of the element distributions in supernova remnants (SNRs) offer important clues for understanding the explosion and nucleosynthesis mechanisms for SNe Ia. However, it is challenging to observe the entire ejecta mass in X-rays for young SNRs, because the central ejecta may not have been heated by the reverse shock yet. Here we present over 200 kilosecond Chandra observations of the Type Ia SNR G344.7-0.1, whose age is old enough for the reverse shock to have reached the SNR center, providing an opportunity to investigate the distribution of the entire ejecta mass. We reveal a clear stratification of heavy elements with a centrally peaked distribution of the Fe ejecta surrounded by intermediate-mass elements (IMEs: Si, S, Ar Ca) with an arc-like structure. The centroid energy of the Fe K emission is marginally lower in the central Fe-rich region than in the outer IME-rich regions, suggesting that the Fe ejecta were shock-heated more recently. These results are consistent with the prediction for standard SN Ia models, where the heavier elements are synthesized in the interior of an exploding white dwarf. We find, however, that the peak location of the Fe K emission is slightly offset to the west with respect to the geometric center of the SNR. This apparent asymmetry is likely due to the inhomogeneous density distribution of the ambient medium, consistent with our radio observations of the ambient molecular and neutral gas.

Keywords: supernova remnants; interstellar medium