adsabs/SciX_UAT_keywords huggingface dataset:
The MAVERIC Survey: Chandra/ACIS Catalog of Faint X-Ray Sources in 38 Galactic Globular Clusters

Globular clusters host a variety of lower-luminosity (LX < 1035 erg s-1) X-ray sources, including accreting neutron stars (NSs) and black holes (BHs), millisecond pulsars (MSPs), cataclysmic variables, and chromospherically active binaries. In this paper, we provide a comprehensive catalog of more than 1100 X-ray sources in 38 Galactic globular clusters (GCs) observed by the Chandra X-ray Observatory's Chandra/ACIS detector. The targets are selected to complement the MAVERIC survey's deep radio continuum maps of Galactic GCs. We perform photometry and spectral analysis for each source, determine a best-fit model, and assess the possibility of it being a foreground or background source based on its spectral properties and location in the cluster. We also provide basic assessments of variability. We discuss the distribution of X-ray binaries in GCs and their X-ray luminosity function, and we carefully analyze systems with LX > 1033 erg s-1. Among these moderately bright systems, we discover a new source in NGC 6539 that may be a candidate accreting stellar-mass BH or a transitional MSP. We show that quiescent NS low-mass X-ray binaries in GCs may spend ∼2% of their lifetimes as transitional MSPs in their active (LX > 1033 erg s-1) state. Finally, we identify a substantial underabundance of bright (LX > 1033 erg s-1) intermediate polars in GCs compared to the Galactic field, in contrast with the literature of the past two decades.

Keywords: globular star clusters; low-mass x-ray binary stars; neutron stars; astrophysical black holes; stellar accretion disks; celestial objects catalogs
The Importance of Local Interstellar Conditions on the Galactic Cosmic-Ray Spectrum at Exoplanets

Galactic cosmic rays (GCRs) are highly energetic particles that can have significant effects on the atmospheres and potentially also surfaces of (exo)planets and moons. Their propagation through the Sun's heliosphere and their interaction with planetary bodies have been widely studied in the solar system (e.g., Earth, Mars, Venus, and Europa). There is currently much interest in exoplanetary science, particularly in terms of characterizing the potential habitability of exoplanetary environments. As a consequence of this, models have been developed to quantify the effect of GCRs on exoplanet systems. However, many such studies assume Earth-like (1 au) GCR fluxes. Here we will demonstrate why this is not a reasonable assumption. We briefly discuss the journey that GCRs make from their birth to the arrival at an exoplanet, and discuss the various implications this will have on GCR fluxes. We demonstrate the importance of understanding the specific local interstellar medium (ISM) that an exoplanetary system resides within, as this determines the size of the astrosphere of the host star. This has strong implications for the modulation of GCR fluxes throughout an astrosphere. We estimate how GCR proton fluxes at 1 au (from the Sun) would be different from current values if the solar system was embedded in a different ISM environment. Furthermore, we provide estimates of the wide range of possible GCR proton fluxes at the exoplanets Kepler-20f and Kepler-88c using previously published estimates for the local ISM parameters at these bodies.

Keywords: habitable planets; exoplanets; astrospheres; galactic cosmic rays
Optical Polarimetry of the Tidal Disruption Event AT2019DSG

We present time-series imaging polarimetry observations of a nearby tidal disruption event (TDE) AT2019DSG at z = 0.0512 to probe the disruption mechanism and shed light on the accretion process. We obtain linear polarimetry using the Alhambra Faint Object Spectrograph and Camera on board the 2.5 m Nordic Optical Telescope. Our observations showed a polarization at the 9.2% ± 2.7% level early on, decreasing to less than 2.7% (at the 68% confidence level) one month later. While the high level of polarization in the early epoch is similar to that of Swift J164449.3+573451 and Swift J2058+0516, the low level of polarization in the later epoch is in agreement with that of OGLE16aaa. Our results thus show the temporal evolution of optical polarization from a TDE. As the degree of polarization changes over time, it is unlikely to be attributed to host galaxy dust, but may originate from a non-isotropic accreting disk, or associated with the relativistic jet emission.

Keywords: tidal disruption; polarimetry
Successive Interacting Coronal Mass Ejections: How to Create a Perfect Storm

Coronal mass ejections (CMEs) are the largest type of eruptions on the Sun and the main driver of severe space weather at the Earth. In this study, we implement a force-free spheromak CME description within 3D magnetohydrodynamic simulations to parametrically evaluate successive interacting CMEs within a representative heliosphere. We explore CME-CME interactions for a range of orientations, launch time variations, and CME handedness and quantify their geo-effectiveness via the primary solar wind variables and empirical measures of the disturbance storm time index and subsolar magnetopause standoff distance. We show how the interaction of two moderate CMEs between the Sun and the Earth can translate into extreme conditions at the Earth and how CME-CME interactions at different radial distances can maximize different solar wind variables that induce different geophysical impacts. In particular, we demonstrate how the orientation and handedness of a given CME can have a significant impact on the conservation and loss of magnetic flux, and consequently B z , due to magnetic reconnection with the interplanetary magnetic field. This study thus implicates the identification of CME chirality in the solar corona as an early diagnostic for forecasting geomagnetic storms involving multiple CMEs.

Keywords: magnetohydrodynamical simulations; solar coronal mass ejections; space weather; heliosphere; magnetic storms; solar storm; solar wind; space plasmas; interplanetary shocks; habitable planets
MOA-2006-BLG-074: Recognizing Xallarap Contaminants in Planetary Microlensing

MOA-2006-BLG-074 was selected as one of the most promising planetary candidates in a retrospective analysis of the MOA collaboration: its asymmetric high-magnification peak can be perfectly explained by a source passing across a central caustic deformed by a small planet. However, after a detailed analysis of the residuals, we have realized that a single lens and a source orbiting with a faint companion provides a more satisfactory explanation for all the observed deviations from a Paczynski curve and the only physically acceptable interpretation. Indeed the orbital motion of the source is constrained enough to allow a very good characterization of the binary source from the microlensing light curve. The case of MOA-2006-BLG-074 suggests that the so-called xallarap effect must be taken seriously in any attempts to obtain accurate planetary demographics from microlensing surveys.

Keywords: gravitational microlensing exoplanet detection; binary stars; binary source microlensing; xallarap effect
Effects of Galaxy Intrinsic Alignment on Weak Lensing Peak Statistics

The galaxy intrinsic alignment (IA) is a dominant source of systematics in weak lensing (WL) studies. In this paper, by employing large simulations with semianalytical galaxy formation, we investigate the IA effects on WL peak statistics. Different simulated source galaxy samples of different redshift distributions are constructed, where both WL shear and IA signals are included. Convergence reconstruction and peak statistics are then performed for these samples. Our results show that the IA effects on peak abundances mainly consist of two aspects. One is the additional contribution from IA to the shape noise. The other is from the satellite IA that can affect the peak signals from their host clusters significantly. The latter depends on the level of inclusion in a shear sample of the satellite galaxies of the clusters that contribute to WL peaks and thus is sensitive to the redshift distribution of source galaxies. We pay particular attention to satellite IA and adjust it artificially in the simulations to analyze the dependence of the satellite IA impacts on its strength. This information can potentially be incorporated into the modeling of WL peak abundances, especially for high peaks physically originated from massive clusters of galaxies, and thus mitigate the IA systematics on the cosmological constraints derived from WL peaks.

Keywords: weak gravitational lensing
Properties of Galactic B[e] Supergiants. V. 3 Pup-Constraining the Orbital Parameters and Modeling the Circumstellar Environments

We report the results of long-term spectroscopic monitoring of the A-type supergiant with the B[e] phenomenon 3 Pup = HD 62623. We confirm earlier findings that it is a binary system. The orbital parameters were derived using cross-correlation of the spectra in a range of 4460-4632 Å, which contains over 30 absorption lines. The orbit was found to be circular with a period of 137.4 ± 0.1 days, radial velocity semiamplitude K1 = 5.0 ± 0.8 km s-1, systemic radial velocity γ = +26.4 ± 2.0 km s-1, and mass function $f(m)=({1.81}_{-0.76}^{+0.97})\times {10}^{-3}$ M⊙. The object may have evolved from a pair with initial masses of ∼6.0 ${M}_{\odot }$ and ∼3.6 M⊙ with an initial orbital period of ∼5 days. Based on the fundamental parameters of the A-supergiant (luminosity log L/L⊙ = 4.1 ± 0.1 and effective temperature Teff = 8500 ± 500 K) and evolutionary tracks of mass-transferring binaries, we found current masses of the gainer M2 = 8.8 ± 0.5 M⊙ and donor M1 = 0.75 ± 0.25 M⊙. We also modeled the object's IR-excess and derived a dust mass of ∼5 × 10-5 M⊙ in the optically thin dusty disk. The orbital parameters and properties of the Hα line profile suggest that the circumstellar gaseous disk is predominantly circumbinary. The relatively low mass of the gainer led us to a suggestion that 3 Pup should be excluded from the B[e] supergiant group and moved to the FS CMa group. Overall these results further support our original suggestion that FS CMa objects are binary systems, where an earlier mass transfer caused formation of the circumstellar envelope.

Keywords: high resolution spectroscopy; emission line stars; binary stars
Beyond Two-dimensional Mass-Radius Relationships: A Nonparametric and Probabilistic Framework for Characterizing Planetary Samples in Higher Dimensions

Fundamental to our understanding of planetary bulk compositions is the relationship between their masses and radii, two properties that are often not simultaneously known for most exoplanets. However, while many previous studies have modeled the two-dimensional relationship between planetary mass and radii, this approach largely ignores the dependencies on other properties that may have influenced the formation and evolution of the planets. In this work, we extend the existing nonparametric and probabilistic framework of MRExo to jointly model distributions beyond two dimensions. Our updated framework can now simultaneously model up to four observables, while also incorporating asymmetric measurement uncertainties and upper limits in the data. We showcase the potential of this multidimensional approach to three science cases: (i) a four-dimensional joint fit to planetary mass, radius, insolation, and stellar mass, hinting of changes in planetary bulk density across insolation and stellar mass; (ii) a three-dimensional fit to the California Kepler Survey sample showing how the planet radius valley evolves across different stellar masses; and (iii) a two-dimensional fit to a sample of Class-II protoplanetary disks in Lupus while incorporating the upper limits in dust mass measurements. In addition, we employ bootstrap and Monte Carlo sampling to quantify the impact of the finite sample size as well as measurement uncertainties on the predicted quantities. We update our existing open-source user-friendly MRExo Python package with these changes, which allows users to apply this highly flexible framework to a variety of data sets beyond what we have shown here.

Keywords: exoplanets; computational methods; astrostatistics tools; algorithms
The Arecibo Observatory as an Instrument for Investigating Orbital Debris: Legacy and Next Generation Performance

In this paper, we investigate the ability of the Arecibo Observatory to characterize the orbital debris environment and compare it to the primary instrument used by NASA's Orbital Debris Program Office, the Haystack Ultra-Wideband Satellite Imaging Radar (HUSIR). Arecibo's location (18.°3 N) increases the percentage of observable orbits (relative to HUSIR) by 27%, which gives Arecibo access to a much larger and previously unmeasured portion of the environment. Due to the recent collapse of the Arecibo dish, in addition to exploring historic capabilities of the Legacy Arecibo Telescope, estimates of the performance of the proposed Next Generation Arecibo Telescope (NGAT) are explored. We show that the current NGAT design could have a sensitivity comparable to the Goldstone Orbital Debris Radar, currently NASA's most sensitive orbital debris radar. Additionally, design suggestions are presented that would significantly improve the capabilities of the NGAT for orbital debris investigations. We show that, with appropriate hardware upgrades, it would be possible to achieve a minimum-detectable debris size as small as 1 mm. These capabilities would allow data from Arecibo to significantly improve short-term debris environment models, which are used to inform spacecraft design and operations, particularly for orbital debris smaller than 3 mm, which pose the highest penetration risk to most spacecraft.

Keywords: space debris; radar telescopes
T-ReX: The Tarantula—Revealed by X-Rays

The Tarantula Nebula (30 Doradus, 30 Dor) is the most important star-forming complex in the Local Group, offering a microscope on starburst astrophysics. At its heart lies the exceptionally rich young stellar cluster R136, containing the most massive stars known. Stellar winds and supernovae have carved 30 Dor into an amazing display of arcs, pillars, and bubbles. We present first results and advanced data-processing products from the 2 Ms Chandra X-ray Visionary Project, "The Tarantula—Revealed by X-rays" (T-ReX). The 3615 point sources in the T-ReX catalog include massive stars, compact objects, binaries, bright pre-main-sequence stars, and compact young stellar (sub)clusters in 30 Dor. After removing point sources and excluding the exceptionally bright supernova remnant N157B (30 Dor B), the global diffuse X-ray maps reveal hot plasma structures resolved at 1–10 pc scales, with an absorption-corrected total-band (0.5–7 keV) X-ray luminosity of 2.110 × 1037 erg s‑1. Spatially resolved spectral modeling provides evidence for emission lines enhanced by charge-exchange processes at the interfaces. We identify a candidate for the oldest X-ray pulsar detected to date in 30 Dor, PSR J0538-6902, inside a newly resolved arcuate X-ray wind nebula, the Manta Ray. The long temporal baseline of T-ReX allowed monitoring of dozens of massive stars, several showing periodic variability tied to binary orbital periods, and captured strong flares from at least three low-mass Galactic foreground stars.

Keywords: h ii regions; high energy astrophysics; early-type stars; star formation; interstellar medium; superbubbles
Shock Cooling Emission from Extended Material Revisited

Following shock breakout, the emission from an astrophysical explosion is dominated by the radiation of shock-heated material as it expands and cools, known as shock cooling emission (SCE). The luminosity of SCE is proportional to the initial radius of the emitting material, which makes its measurement useful for investigating the progenitors of these explosions. Recent observations have shown some transient events have especially prominent SCE, indicating a large radius that is potentially due to low-mass extended material. Motivated by this, we present an updated analytic model for SCE that can be utilized to fit these observations and learn more about the origin of these events. This model is compared with numerical simulations to assess its validity and limitations. We also discuss SN 2016gkg and SN 2019dge, two transients with large early luminosity peaks that have previously been attributed to SCE of extended material. We show that their early power-law evolution and photometry are well matched by our model, strengthening support for this interpretation.

Keywords: radiative transfer; supernovae
Recombination Lines and Molecular Gas from Hypercompact H II regions in W51 A

We present a detailed characterization of the population of compact radio-continuum sources in W51 A using subarcsecond Very Large Array and Atacama Large Millimeter/submillimeter Array observations. We analyze their 2 cm continuum, the recombination lines (RLs) H77α and H30α, and the lines of ${{\rm{H}}}_{2}\mathrm{CO}({3}_{\mathrm{0,3}}-{2}_{\mathrm{0,2}})$ , ${{\rm{H}}}_{2}\mathrm{CO}({3}_{\mathrm{2,1}}-{2}_{\mathrm{2,0}})$ , and $\mathrm{SO}({6}_{5}-{5}_{4})$ . We derive diameters for 10/20 sources in the range D ∼ 10-3 to ∼10-2 pc, thus placing them in the regime of hypercompact H II regions (HC H II's). Their continuum-derived electron densities are in the range ne ∼ 104 -105 cm-3, lower than typically considered for HC H II's. We combined the RL measurements and independently derived ne, finding the same range of values but significant offsets for individual measurements between the two methods. We find that most of the sources in our sample are ionized by early B-type stars, and a comparison of ne versus D shows that they follow the inverse relation previously derived for ultracompact (UC) and compact H II's. When determined, the ionized-gas kinematics is always (7/7) indicative of outflow. Similarly, 5 and 3 out of the 8 HC H II's still embedded in a compact core show evidence for expansion and infall motions in the molecular gas, respectively. We hypothesize that there could be two different types of hypercompact (D < 0.05 pc) H II regions: those that essentially are smaller, expanding UC H II's; and those that are also hyperdense (ne > 106 cm-3), probably associated with O-type stars in a specific stage of their formation or early life.

Keywords: h ii regions; star formation; radio astronomy; giant molecular clouds
The Energetic Thermonuclear Bursts in SAX J1712.6-3739

The neutron star low-mass X-ray binary SAX J1712.6-3739 is known for its long and hard thermonuclear X-ray bursts from previous observations. Its thermonuclear bursts are so distinct as they can last for tens of minutes, as seen with Swift/BAT (E > 15 keV). To explore the origin of these extreme bursts and the nature of SAX J1712.6-3739, we analyzed the observations of all four bursts that were captured by Swift/BAT and derived the peak flux and the fluence of these bursts from joint studies with Swift/XRT and Swift/BAT. The derived bolometric peak fluxes observed by Swift set the distance of SAX J1712.6-3739 to be 4.6-5.6 kpc, while the derived absolute magnitude and average accretion rate agree with its ultracompact nature. Our measurements of the effective duration of these bursts conclude that the 2010 burst corresponds to a normal X-ray burst, the 2011 burst is consistent with an intermediate-duration burst, while the 2014 and the 2018 bursts are more energetic than common intermediate-duration bursts but less energetic than those known superbursts. We estimated that the average mass accretion rate of SAX J1712.6-3739 was about only 0.4%-0.7% ${\dot{{\text{}}M}}_{\mathrm{Edd}}$ . Current theory predicts no carbon production in the bursters under such low accretion rate. If true, the 2014 and 2018 bursts are then deep helium bursts instead of carbon bursts. The thermonuclear bursts of SAX J1712.6-3739 have shown a very wide range of durations. The ignition model predicts that the diverse burst durations are induced by variable accretion rates, but current results provide only weak support to this inference.

Keywords: x-ray bursts; neutron stars; x-ray binary stars
Polarimetric Geometric Modeling for mm-VLBI Observations of Black Holes

The Event Horizon Telescope (EHT) is a millimeter very long baseline interferometry (VLBI) array that has imaged the apparent shadows of the supermassive black holes M87* and Sagittarius A*. Polarimetric data from these observations contain a wealth of information on the black hole and accretion flow properties. In this work, we develop polarimetric geometric modeling methods for mm-VLBI data, focusing on approaches that fit data products with differing degrees of invariance to broad classes of calibration errors. We establish a fitting procedure using a polarimetric "m-ring" model to approximate the image structure near a black hole. By fitting this model to synthetic EHT data from general relativistic magnetohydrodynamic models, we show that the linear and circular polarization structure can be successfully approximated with relatively few model parameters. We then fit this model to EHT observations of M87* taken in 2017. In total intensity and linear polarization, the m-ring fits are consistent with previous results from imaging methods. In circular polarization, the m-ring fits indicate the presence of event-horizon-scale circular polarization structure, with a persistent dipolar asymmetry and orientation across several days. The same structure was recovered independently of observing band, used data products, and model assumptions. Despite this broad agreement, imaging methods do not produce similarly consistent results. Our circular polarization results, which imposed additional assumptions on the source structure, should thus be interpreted with some caution. Polarimetric geometric modeling provides a useful and powerful method to constrain the properties of horizon-scale polarized emission, particularly for sparse arrays like the EHT.

Keywords: active galactic nuclei; supermassive black holes; black hole physics; high angular resolution; very long baseline interferometry; polarimetry
A Multiwavelength Survey of Wolf-Rayet Nebulae in the Large Magellanic Cloud

Surveys of Wolf-Rayet (WR) stars in the Large Magellanic Cloud (LMC) have yielded a fairly complete catalog of 154 known stars. We have conducted a comprehensive, multiwavelength study of the interstellar/circumstellar environments of WR stars, using the Magellanic Cloud Emission Line Survey images in the Hα, [O III], and [S II] lines; Spitzer Space Telescope 8 and 24 μm images; Blanco 4 m Telescope Hα CCD images; and Australian Telescope Compact Array + Parkes Telescope H I data cube of the LMC. We have also examined whether the WR stars are in OB associations, classified the H II environments of WR stars, and used this information to qualitatively assess the WR stars' evolutionary stages. The 30 Dor giant H II region has active star formation and hosts young massive clusters, thus we have made statistical analyses for 30 Dor and the rest of the LMC both separately and altogether. Due to the presence of massive young clusters, the WR population in 30 Dor is quite different from that from elsewhere in the LMC. We find small bubbles (<50 pc diameter) around ∼12% of WR stars in the LMC, most of which are WN stars and not in OB associations. The scarcity of small WR bubbles is discussed. Spectroscopic analyses of abundances are needed to determine whether the small WR bubbles contain interstellar medium or circumstellar medium. Implications of the statistics of interstellar environments and OB associations around WR stars are discussed. Multiwavelength images of each LMC WR star are presented.

Keywords: wolf-rayet stars; stellar wind bubbles; interstellar medium; large magellanic cloud