adsabs/SciX_UAT_keywords huggingface dataset:
Fermi LAT Gamma-ray Detection of the Recurrent Nova RS Ophiuchi during its 2021 Outburst

We report the Fermi LAT γ-ray detection of the 2021 outburst of the symbiotic recurrent nova RS Ophiuchi. In this system, unlike classical novae from cataclysmic binaries, the ejecta from the white dwarf form shocks when interacting with the dense circumstellar wind environment of the red giant companion. We find the LAT spectra from 50 MeV to ~20-23 GeV, the highest-energy photons detected in some subintervals, are consistent with π 0-decay emission from shocks in the ejecta as proposed by Tatischeff & Hernanz for its previous 2006 outburst. The LAT light curve displayed a fast rise to its peak >0.1 GeV flux of ≃6 × 10-6 ph cm-2 s-1 beginning on day 0.745 after its optically constrained eruption epoch of 2021 August 8.50. The peak lasted for ~1 day and exhibited a power-law decline up to the final LAT detection on day 45. We analyze the data on shorter timescales at early times and found evidence of an approximate doubling of emission over ~200 minutes at day 2.2, possibly indicating a localized shock-acceleration event. Comparing the data collected by the American Association of Variable Star Observers, we measured a constant ratio of ~ 2.8 × 10-3 between the γ-ray and optical luminosities except for a ~5×smaller ratio within the first day of the eruption likely indicating attenuation of γ rays by ejecta material and lower high-energy proton fluxes at the earliest stages of the shock development. The hard X-ray emission due to bremsstrahlung from shock-heated gas traced by the Swift-XRT 2-10 keV light curve peaked at day ~6, later than at GeV and optical energies. Using X-ray derived temperatures to constrain the velocity profile, we find the hadronic model reproduces the observed >0.1 GeV light curve.

Keywords: gamma-ray transient sources; recurrent novae
Origin of Low-26Al/27Al Corundum/Hibonite Inclusions in Meteorites

Most meteoritic calcium-rich, aluminum-rich inclusions formed from a reservoir with 26Al/27Al ≈ 5 × 10-5, but some record lower ${({}^{26}\mathrm{Al}/{}^{27}\mathrm{Al})}_{0}$ , demanding they sampled a reservoir without live 26Al. This has been interpreted as evidence for "late injection" of supernova material into our protoplanetary disk. We instead interpret the heterogeneity as chemical, demonstrating that these inclusions are strongly associated with the refractory phases corundum or hibonite. We name them "low-26Al/27Al corundum/hibonite inclusions" (LAACHIs). We present a detailed astrophysical model for LAACHI formation in which they derive their Al from presolar corundum, spinel, or hibonite grains 0.5-2 μm in size with no live 26Al; live 26Al is carried on smaller (<50 nm) presolar chromium spinel grains from recent nearby Wolf-Rayet stars or supernovae. In hot (≈1350-1425 K) regions of the disk, these grains and perovskite grains would be the only survivors. These negatively charged grains would grow to sizes 1-103 μm, even incorporating positively charged perovskite grains, but not the small, negatively charged 26Al-bearing grains. Chemical and isotopic fractionations due to grain charging was a significant process in hot regions of the disk. Our model explains the sizes, compositions, oxygen isotopic signatures, and the large, correlated 48Ca and 50Ti anomalies (if carried by presolar perovskite) of LAACHIs, and especially how they incorporated no 26Al in a solar nebula with uniform, canonical 26Al/27Al. A late injection of supernova material is obviated, although formation of the Sun in a high-mass star-forming region is demanded.

Keywords: meteorites; supernovae; protoplanetary disks; solar system formation; dust physics
Shock Breakout in Dense Circumstellar Material with Application to PS1-13arp

Shock breakout (SBO), the first expected electromagnetic signature of a supernova (SN), can be an important probe of the progenitors of these explosions. Unfortunately, SBO is difficult to capture with current surveys due to its brief timescale (≲1 hr). However, SBO may be lengthened when dense circumstellar material (CSM) is present. Indeed, recent photometric modeling studies of SNe, as well as early spectroscopy, suggest that such dense CSM may be present more often than previously expected. If true, this should also affect the features of SBO. We present an exploration of the impact of such CSM interaction on the SBO width and luminosity using both analytic and numerical modeling, where we parameterize the CSM as a steady-state wind. We then compare this modeling to PS1-13arp, an SN that showed an early UV excess that has been argued to be SBO in dense CSM. We find PS1-13arp is well fit with a wind of mass ∼0.08 M⊙ and radius ∼1900 R⊙, parameters which are similar to, if not slightly less massive than, what have been inferred for Type II SNe using photometric modeling. This similarity suggests that future SBO observations of SNe II may be easier to obtain than previously appreciated.

Keywords: radiative transfer; supernovae
The breakBRD Breakdown: Using IllustrisTNG to Track the Quenching of an Observationally Motivated Sample of Centrally Star-forming Galaxies

The observed breakBRD ("break bulges in red disks") galaxies are a nearby sample of face-on disk galaxies with particularly centrally concentrated star formation: they have red disks but recent star formation in their centers as measured by the Dn4000 spectral index. In this paper, we search for breakBRD analogs in the IllustrisTNG simulation and describe their history and future. We find that a small fraction (∼4% at z = 0; ∼1% at z = 0.5) of galaxies fulfill the breakBRD criteria, in agreement with observations. In comparison with the mass-weighted parent IllustrisTNG sample, these galaxies tend to consist of a higher fraction of satellite and splashback galaxies. However, the central, non-splashback breakBRD galaxies show similar environments, black hole masses, and merger rates, indicating that there is not a single formation trigger for inner star formation and outer quenching. We determine that breakBRD analog galaxies as a whole are in the process of quenching. The breakBRD state, with its highly centrally concentrated star formation, is uncommon in the history of either currently quiescent or star-forming galaxies; however, approximately 10% of 1010 < M*/M⊙ < 1011 quiescent galaxies at z = 0 have experienced SFR concentrations comparable to those of the breakBRDs in their past. Additionally, the breakBRD state is short lived, lasting a few hundred Myr up to ∼2 Gyr. The observed breakBRD galaxies may therefore be a unique sample of outside-in quenching galaxies.

Keywords: galaxy processes; galaxy physics; galaxy evolution; galaxy quenching; galaxy environments; astronomical simulations
Resolved Stellar Mass Maps of Galaxies in the Hubble Frontier Fields: Evidence for Mass Dependency in Environmental Quenching

One of the challenges in understanding the quenching processes for galaxies is connecting progenitor star-forming populations to their descendant quiescent populations over cosmic time. Here we attempt a novel approach to this challenge by assuming that the underlying stellar mass distribution of galaxies is not significantly altered during environmental-quenching processes that solely affect the gas content of cluster galaxies, such as strangulation and ram pressure stripping. Using the deep, high-resolution photometry of the Hubble Frontier Fields, we create resolved stellar mass maps for both cluster and field galaxies, from which we determine 2D Sérsic profiles, and obtain Sérsic indices and half-mass radii. We classify the quiescent cluster galaxies into disk-like and bulge-like populations based on their Sérsic indices, and find that bulge-like quiescent galaxies dominate the quiescent population at higher masses (M ⋆ > 109.5 M ⊙), whereas disk-like quiescent galaxies dominate at lower masses (108.5 M ⊙ < M ⋆ < 109.5 M ⊙). Using both the Sérsic indices and half-mass radii, we identify a population of quiescent galaxies in clusters that are morphological analogs of field star-forming galaxies. These analogs are interpreted to be star-forming galaxies that had been environmentally quenched. We use these morphological analogs to compute the environmental-quenching efficiency, and we find that the efficiency decreases with increasing stellar mass. This demonstrates that environmental quenching is more effective on less massive galaxies and that the effect of environment on quenching galaxies is not completely separable from the effect of mass on quenching galaxies.

Keywords: galaxy evolution; galaxy quenching; galaxy processes; galaxy clusters; galactic and extragalactic astronomy; galaxy classification systems; galaxies
Modeling Saturn's D68 Clumps as a Co-orbital Satellite System

The D68 ringlet is the innermost feature in Saturn's rings. Four clumps that appeared in D68 around 2014 remained evenly spaced about 30° apart and moved very slowly relative to each other from 2014 up until the last measurements were taken in 2017. D68's narrowness and the distribution of clumps could either indicate that we have a collection of source bodies in a co-orbital configuration or imply that an outside force confines the observed dust and any source bodies. In this paper we explore the possibility that these four clumps arose from four source bodies in a co-orbital configuration. We find that there are no solutions with four masses that produce the observed spacings. We therefore consider whether an unseen fifth co-orbital object could account for the discrepancies in the angular separations and approach a stable stationary configuration. We find a range of solutions for five co-orbital objects where their mass ratios depend on the assumed location of the fifth mass. Numerical simulations of five co-orbitals are highly sensitive to initial conditions, especially for the range of masses we would expect the D68 clumps to have. The fragility of our D68 co-orbital system model implies that there is probably some outside force confining the material in this ringlet.

Keywords: planetary rings; orbits; dynamical evolution
Unlocking the Origins of Ultracool Dwarf Radio Emission

Empirical trends in stellar X-ray and radio luminosities suggest that low-mass ultracool dwarfs (UCDs) should not produce significant radio emission. Defying these expectations, strong nonthermal emission has been observed in a few UCDs in the 1-10 GHz range, with a variable component often attributed to global aurorae and a steady component attributed to other processes, such as gyrosynchrotron emission. While both auroral and gyrosynchrotron emission peak near the critical frequency, only the latter radiation is expected to extend into millimeter wavelengths. We present Atacama Large Millimetre/Submillimeter Array (ALMA) 97.5 GHz and Very Large Array 33 GHz observations of a small survey of 5 UCDs. LP 349-25, LSR J1835+3259, and NLTT 33370 were detected at 97.5 GHz, while LP 423-31 and LP 415-20 resulted in nondetections at 33 GHz. A significant flare was observed in NLTT 33370, which reached a peak flux of 4880 ± 360 μJy, exceeding the quiescent flux by nearly an order of magnitude and lasting 20 s. These ALMA observations show bright 97.5 GHz emission with spectral indices ranging from α = 0.76 to α = -0.29, suggestive of optically thin gyrosynchrotron emission. If such emission traces magnetic reconnection events, then this could have consequences for both UCD magnetic models and the atmospheric stability of planets in orbit around them. Overall, our results provide confirmation that gyrosynchrotron radiation in radio-loud UCDs can remain detectable into the millimeter regime.

Keywords: late-type stars; m dwarf stars; space weather; radio continuum emission
A Characterization of the Circumstellar Gas of WD 1124-293 Using Cloudy

Between 30% and 50% of white dwarfs (WDs) show heavy elements in their atmospheres. This pollution is thought to arise from the accretion of planetesimals perturbed by outer planet(s) to within the WD's tidal disruption radius. A small fraction of these WDs show either emission or absorption from circumstellar (C-S) gas. The abundances of metals in the photospheres of WDs with C-S gas are mostly similar to the bulk composition of the Earth. The C-S component arises from gas produced through collisions and/or the sublimation of disintegrating planetesimals. High-resolution spectroscopic observations of WD 1124-293 reveal photospheric and C-S absorption of Ca in multiple transitions. Here, we present high signal-to-noise ratio spectra, an updated WD atmosphere analysis, and a self-consistent model of its C-S gas. We constrain the abundances of Ca, Mg, and Fe in the photosphere of WD 1124-293, and find agreement with the abundances of these three species in the C-S gas. We find the location of the C-S gas is ∼100 white dwarf radii, the C-S and photospheric compositions are thus far consistent, the gas is not isothermal, and the amount of C-S Ca has not changed in two decades. We also demonstrate how to use Cloudy to model C-S gas viewed in absorption around polluted WDs. Modeling the abundances of gas around polluted WDs with Cloudy provides a new method to measure the composition of exoplanetesimals and will allow a direct comparison to the composition of rocky bodies in the solar system.

Keywords: extrasolar rocky planets; white dwarf stars; da stars
MeerKAT Holography Measurements in the UHF, L, and S Bands

Radio holographic measurements using the MeerKAT telescope are presented for each of its supported observing bands, namely UHF (544-1087 MHz), L (856-1711 MHz), and S (1750-3499 MHz). Because the UHF-band receiver design is a scaled version of that of the L band, the electromagnetic performance in these two bands are expectedly similar to one another. Despite also being linearly polarized, S-band receivers have an entirely different design and distinct performance characteristics from the lower two bands. As introduced in previous work for the L band, evidence of higher order waveguide mode activation also appears in S-band measurements but there are differences in its manifestation. Frequency-dependent pointing (beam squint), beamwidth, beam ellipticity, error beam, instrumental polarization, and cross-polarization power measurements are illustrated for each of MeerKAT's observational bands in a side-by-side style to facilitate the comparison of features. The derivation of collimation errors and main reflector surface errors from measurements made at these relatively low observation frequencies is also discussed. Results include elevation and ambient temperature effects on collimation, as well as the signatures of collimation degrading over time. The accompanying data release includes a snapshot of full Jones matrix primary beam patterns for all bands and antennas with corresponding derived metrics.

Keywords: interferometers; observational astronomy; polarimetry
Formation of Post-CME Blobs Observed by LASCO-C2 and K-Cor on 2017 September 10

Understanding the formation of post-CME blobs, we investigate 2 blobs in the outer corona observed by LASCO-C2 and 34 blobs in the inner corona by K-Cor on 2017 September 10 from 17:11 to 18:58 UT. By visual inspection of the structure of a post-CME current sheet (CS) and its associated blobs, we find that the CS is well identified in the K-Cor and its radial lengths are nine times longer than lateral widths, indicating the CS is unstable to the linear tearing mode. The inner corona blobs can be classified into two groups: 27 blobs generated in the middle of the CS (Group 1) and 7 blobs occurred above the tips of it (Group 2). Their lateral widths are < 0.02 R⊙ > and < 0.05 R⊙>, which is smaller than, or similar to, those (< 0.06 R⊙ >) of the CS. They have elongated shapes: ratios of lateral to radial widths are < 0.53 > and < 0.40 >, respectively. In the first group, only three blobs propagate above the tip of the CS while the others are located in the CS. In the second group, only two blobs have associations with those of outer corona in their temporal and spatial relationship and their initial heights are 1.81 and 1.95 R⊙, measured from the center of the Sun. The others cannot be identified in the outer corona. Our results first demonstrate that LASCO-C2 blobs could be generated by the tearing mode instability near the tips of post-CME CSs, similar to the magnetic reconnection process in the tail CS of Earth's magnetosphere.

Keywords: solar magnetic reconnection; solar corona; solar coronal mass ejections
Calibrating VLBI Polarization Data Using GPCAL. II. Time-dependent Calibration

We present a new method of time-dependent instrumental polarization calibration for very long baseline interferometry (VLBI). This method has been implemented in the recently developed polarization calibration pipeline GPCAL. Instrumental polarization, also known as polarimetric leakage, is a direction-dependent effect, and it is not constant across the beam of a telescope. Antenna pointing model accuracy is usually dependent on time, resulting in off-axis polarimetric leakages that can vary with time. The method is designed to correct for the off-axis leakages with large amplitudes that can severely degrade linear polarization images. Using synthetic data generated based on real Very Long Baseline Array (VLBA) data observed at 43 GHz, we evaluate the performance of the method. It was able to reproduce the off-axis leakages assumed in the synthetic data, particularly those with large amplitudes. The method has been applied to two sets of real VLBA data, and the derived off-axis leakages show very similar trends over time for pairs of nearby sources. Furthermore, the amplitudes of the off-axis leakages are strongly correlated with the antenna gain correction factors. The results demonstrate that the method is capable of correcting for the off-axis leakages present in VLBI data. By calibrating time-dependent instrumental polarization, the rms noise levels of the updated linear polarization images have been significantly reduced. The method is expected to substantially enhance the quality of linear polarization images obtained from existing and future VLBI observations.

Keywords: astronomy software; high angular resolution; very long baseline interferometry; polarimetry; supermassive black holes; relativistic jets; astronomy data analysis
Surface Brightness Fluctuations in Two SPT Clusters: A Pilot Study

Studies of surface brightness fluctuations in the intracluster medium present an indirect probe of turbulent properties such as the turbulent velocities, injection scales, and the slope of the power spectrum of fluctuations toward smaller scales. With the advancement of Sunyaev–Zel'dovich (SZ) studies and surveys relative to X-ray observations, we seek to investigate surface brightness fluctuations in a sample of South Pole Telescope (SPT)-SZ clusters which also have archival XMM-Newton data. Here we present a pilot study of two typical clusters in that sample: SPT-CLJ0232-4421 and SPT-CLJ0638-5358. We infer injection scales larger than 500 kpc in both clusters and Mach numbers ≈ 0.5 in SPT-CLJ0232-4421 and Mach numbers ≈ 0.6–1.6 in SPT-CLJ0638-5358, which has a known shock. We find hydrostatic bias values for M 500 less than 0.2 for SPT-CLJ0232-4421 and less than 0.1 for SPT-CLJ0638-5358. These results show the importance to assess quantitative values via a detailed multiwavelength approach and suggest that the drivers of turbulence may occur at quite large scales.

Keywords: galaxy clusters; intracluster medium
Pulsar Glitch Detection with a Hidden Markov Model

Pulsar timing experiments typically generate a phase-connected timing solution from a sequence of times of arrival (TOAs) by absolute pulse numbering, I.e., by fitting an integer number of pulses between TOAs in order to minimize the residuals with respect to a parameterized phase model. In this observing mode, rotational glitches are discovered, when the residuals of the no-glitch phase model diverge after some epoch, and glitch parameters are refined by Bayesian follow-up. Here, we present an alternative, complementary approach which tracks the pulse frequency f and its time derivative $\dot{f}$ with a hidden Markov model (HMM), whose dynamics include stochastic spin wandering (timing noise) and impulsive jumps in f and $\dot{f}$ (glitches). The HMM tracks spin wandering explicitly, as a specific realization of a discrete-time Markov chain. It discovers glitches by comparing the Bayes factor for glitch and no-glitch models. It ingests standard TOAs for convenience, and being fully automated, allows performance bounds to be calculated quickly via Monte Carlo simulations. Practical, user-oriented plots of the false-alarm probability and detection threshold (e.g., minimum resolvable glitch size) versus observational scheduling parameters (e.g., TOA uncertainty, mean delay between TOAs) and glitch parameters (e.g., transient and permanent jump sizes, exponential recovery timescale) are presented. The HMM is also applied to ∼1 yr of real data bracketing the 2016 December 12 glitch in PSR J0835-4510 as a proof of principle. It detects the known glitch and confirms that no other glitch exists in the same data with size ≳10-7f.

Keywords: pulsars; neutron stars; stellar rotation; gravitational waves
Variations in the Pickup Ion Density Structure in Response to the Growth of the Kelvin-Helmholtz Instability along the Heliopause

Features of the response of pickup ions (PUIs) to the Kelvin-Helmholtz instability (KHI) on the heliopause (HP) are examined by means of two-dimensional hybrid simulations. We assume the supersonic neutral solar wind as the source of PUIs gyrating about the magnetic field in the outer heliosheath. These PUIs become energetic neutral atoms (ENAs) via charge exchange with interstellar hydrogen, and a portion of these ENAs are detected by spacecraft such as the Interstellar Boundary Explorer (IBEX). To evaluate the possibility of identifying the KHI on the HP from ENA observations, we assume that an imprint of the KHI may be displayed in spatial and temporal variations in the observed ENA profile. As an alternative to ENA, the column density of PUIs integrated across the HP is calculated. The KH-inducing vortex forces not only background protons but also PUIs to roll up deep in the inner heliosheath. The KH vortex also results in the emission of magnetosonic pulses that sweep PUIs in the outer heliosheath and lead to their local confinement. These effects elongate the PUIs' spatial distribution in the direction normal to the HP. The appearance of the local confined structure in the PUIs' column density is consequently confirmed, and this feature can be confirmed as the KHI evolution. Although the simulation cannot be quantitatively compared with the observations currently available because its resolution is too low, we expect that the derived properties will be useful for diagnosing the nature of HP fluctuation in future missions.

Keywords: pickup ions; heliopause; heliosheath; heliosphere; solar wind
New Light Curves of LP133-373 Reveal Flaring, A Refined Period and an Initial Epoch

We present new CCD Johnson V and Cousins R photometric data on the eclipsing binary LP133-373. Analysis includes the detection of a flare event, eclipse timings and a refined period and initial epoch for the system. The new ephemeris for this system is T = 2452760.70523 ± 0.00045 + 1.6279850 ± 4.3805144 × 10-7 × e. Previous studies by others have mentioned period changes and radial velocity changes over time, so we continue to monitor LP133-373.

Keywords: binary stars; detached binary stars; eclipsing binary stars