adsabs/SciX_UAT_keywords huggingface dataset:
Inferring Parameters of GW170502: The Loudest Intermediate-mass Black Hole Trigger in LIGO's O1/O2 data

Gravitational wave (GW) measurements provide the most robust constraints of the mass of astrophysical black holes. Using state-of-the-art GW signal models and a unique parameter estimation technique, we infer the source parameters of the loudest marginal trigger, GW170502, found by LIGO from 2015 to 2017. If this trigger is assumed to be a binary black hole merger, we find it corresponds to a total mass in the source frame of ${157}_{-41}^{+55}\,{\text{}}{M}_{\odot }$ at redshift $z={1.37}_{-0.64}^{+0.93}$ . The primary and secondary black hole masses are constrained to ${94}_{-28}^{+44}\,{\text{}}{M}_{\odot }$ and ${62}_{-25}^{+30}\,{\text{}}{M}_{\odot }$ , respectively, with 90% confidence. Across all signal models, we find ≳70% probability for the effective spin parameter χeff > 0.1. Furthermore, we find that the inclusion of higher-order modes in the analysis narrows the confidence region for the primary black hole mass by 10%; however, the evidence for these modes in the data remains negligible. The techniques outlined in this study could lead to robust inference of the physical parameters for all intermediate-mass black hole binary candidates (≳100 M⊙) in the current GW network.

Keywords: intermediate-mass black holes; gravitational wave sources
IceCube Search for Neutrinos Coincident with Gravitational Wave Events from LIGO/Virgo Run O3

Using data from the IceCube Neutrino Observatory, we searched for high-energy neutrino emission from the gravitational-wave events detected by the advanced LIGO and Virgo detectors during their third observing run. We did a low-latency follow-up on the public candidate events released during the detectors' third observing run and an archival search on the 80 confident events reported in the GWTC-2.1 and GWTC-3 catalogs. An extended search was also conducted for neutrino emission on longer timescales from neutron star containing mergers. Follow-up searches on the candidate optical counterpart of GW190521 were also conducted. We used two methods; an unbinned maximum likelihood analysis and a Bayesian analysis using astrophysical priors, both of which were previously used to search for high-energy neutrino emission from gravitational-wave events. No significant neutrino emission was observed by any analysis, and upper limits were placed on the time-integrated neutrino flux as well as the total isotropic equivalent energy emitted in high-energy neutrinos.

Keywords: neutrino astronomy; neutrino telescopes; gravitational waves; gravitational wave astronomy; high energy astrophysics
Tracing Hα Fibrils through Bayesian Deep Learning

We present a new deep-learning method, named FibrilNet, for tracing chromospheric fibrils in Hα images of solar observations. Our method consists of a data preprocessing component that prepares training data from a threshold-based tool, a deep-learning model implemented as a Bayesian convolutional neural network for probabilistic image segmentation with uncertainty quantification to predict fibrils, and a post-processing component containing a fibril-fitting algorithm to determine fibril orientations. The FibrilNet tool is applied to high-resolution Hα images from an active region (AR 12665) collected by the 1.6 m Goode Solar Telescope (GST) equipped with high-order adaptive optics at the Big Bear Solar Observatory (BBSO). We quantitatively assess the FibrilNet tool, comparing its image segmentation algorithm and fibril-fitting algorithm with those employed by the threshold-based tool. Our experimental results and major findings are summarized as follows. First, the image segmentation results (i.e., the detected fibrils) of the two tools are quite similar, demonstrating the good learning capability of FibrilNet. Second, FibrilNet finds more accurate and smoother fibril orientation angles than the threshold-based tool. Third, FibrilNet is faster than the threshold-based tool and the uncertainty maps produced by FibrilNet not only provide a quantitative way to measure the confidence on each detected fibril, but also help identify fibril structures that are not detected by the threshold-based tool but are inferred through machine learning. Finally, we apply FibrilNet to full-disk Hα images from other solar observatories and additional high-resolution Hα images collected by BBSO/GST, demonstrating the tool's usability in diverse data sets.

Keywords: solar atmosphere; solar chromosphere; convolutional neural networks
Pair Plasma in Super-QED Magnetic Fields and the Hard X-Ray/Optical Emission of Magnetars

The photon spectrum emitted by a transrelativistic pair plasma is calculated in the presence of an ultrastrong magnetic field, and is shown to bear a remarkable resemblance to the rising hard X-ray spectra of quiescent magnetars. This emission is powered by pair annihilation which, in contrast with a weakly magnetized pair plasma, shows an extended low-frequency tail similar to bremsstrahlung. Cross sections for electron-positron annihilation/scattering, two-photon pair creation, and photon-e± scattering are adopted from our earlier ab initio quantum electrodynamic calculations in the regime $10{\alpha }_{\mathrm{em}}^{-1}{B}_{{\rm{Q}}}$ ≫ B ≫ BQ. Careful attention is given to the u-channel scattering resonance. Magnetospheric arcades anchored in zones of intense crustal shear and reaching about twice the magnetar radius are identified as the sites of the persistent hard X-ray emission. We deduce a novel and stable configuration for the magnetospheric circuit, with a high plasma density sustained by ohmic heating and in situ pair creation. Pairs are sourced nonlocally by photon collisions in zones with weak currents, such as the polar cap. Annihilation bremsstrahlung extends to the optical-IR band, where the plasma cutoff is located. The upper magnetar atmosphere experiences strong current-driven growth of ion-acoustic turbulence, which may limit positron diffusion. Coherent optical-IR emission is bounded near the observed flux by induced scattering. This model accommodates the rapid X-ray brightening of an activating magnetar, concentrated thermal hotspots, and the subdominant thermal X-ray emission of some active magnetars. Current injection is ascribed to continuous magnetic braiding, as seen in the global yielding calculations of Thompson, Yang, and Ortiz.

Keywords: plasma astrophysics; magnetic fields; magnetars; gamma-rays; compact radiation sources
Short-timescale Spatial Variability of Ganymede's Optical Aurora

Ganymede's auroras are the product of complex interactions between its intrinsic magnetosphere and the surrounding Jovian plasma environment and can be used to derive both atmospheric composition and density. In this study, we analyzed a time series of Ganymede's optical auroras taken with Keck I/HIRES during eclipse by Jupiter on 2021 June 8 UTC, one day after the Juno flyby of Ganymede. The data had sufficient signal-to-noise in individual 5 minute observations to allow for the first high-cadence analysis of the spatial distribution of the optical aurora brightness and the ratio between the [O I] 630.0 and 557.7 nm disk-integrated auroral brightnesses—a quantity diagnostic of the relative abundances of O, O2, and H2O in Ganymede's atmosphere. We found that the hemisphere closer to the centrifugal equator of Jupiter's magnetosphere (where electron number density is highest) was up to twice as bright as the opposing hemisphere. The dusk (trailing) hemisphere, subjected to the highest flux of charged particles from Jupiter's magnetosphere, was also consistently almost twice as bright as the dawn (leading) hemisphere. We modeled emission from simulated O2 and H2O atmospheres during eclipse and found that if Ganymede hosts an H2O sublimation atmosphere in sunlight, it must collapse on a faster timescale than expected to explain its absence in our data given our current understanding of Ganymede's surface properties.

Keywords: aurorae; ganymede; natural satellite atmospheres; optical astronomy
Differences between Stable and Unstable Architectures of Compact Planetary Systems

We present a stability analysis of a large set of simulated planetary systems of three or more planets based on architectures of multiplanet systems discovered by Kepler and K2. We propagated 21,400 simulated planetary systems up to 5 billion orbits of the innermost planet; approximately 13% of these simulations ended in a planet–planet collision within that time span. We examined trends in dynamical stability based on dynamical spacings, orbital period ratios, and mass ratios of nearest-neighbor planets as well as the system-wide planet mass distribution and the spectral fraction describing the system's short-term evolution. We find that instability is more likely in planetary systems with adjacent planet pairs that have period ratios less than 2 and in systems of greater variance of planet masses. Systems with planet pairs at very small dynamical spacings (less than ∼10–12 mutual Hill radii) are also prone to instabilities, but instabilities also occur at much larger planetary separations. We find that a large spectral fraction (calculated from short integrations) is a reasonable predictor of longer-term dynamical instability; systems that have a large number of Fourier components in their eccentricity vectors are prone to secular chaos and subsequent eccentricity growth and instabilities.

Keywords: exoplanets; exoplanet dynamics; exoplanet systems; orbital evolution
Coherent Curvature Radio Emission and Polarization from Pulsars

We have developed a collective plasma radio emission model for the radio pulsars based on the implications of the tangent model. The secondary pair (electron-positron) plasma particles get arranged into a phased array like an antenna due to plasma waves and radiate in phase. We have reproduced the polarization profiles by considering different viewing conditions in the pulsars having an oblique dipolar magnetic field. We find that when there is a resonance between the radio and the plasma waves, the flux of emitted radio waves gets enhanced. We numerically estimated the collective radio emission due to relativistic plasma. The model predicts the correlation between the sign reversal circular polarization and the polarization angle swing and the brightness temperature in the range ∼1031-1033 K.

Keywords: radio pulsars
On the Use of Field RR Lyrae as Galactic Probes. V. Optical and Radial Velocity Curve Templates

We collected the largest spectroscopic catalog of RR Lyrae (RRLs) including ≈20,000 high-, medium-, and low-resolution spectra for ≈10,000 RRLs. We provide the analytical forms of radial velocity curve (RVC) templates. These were built using 36 RRLs (31 fundamental-split into three period bins-and five first-overtone pulsators) with well-sampled RVCs based on three groups of metallic lines (Fe, Mg, Na) and four Balmer lines (Hα, Hβ, Hγ, Hδ). We tackled the long-standing problem of the reference epoch to anchor light-curve and RVC templates. For the V-band, we found that the residuals of the templates anchored to the phase of the mean magnitude along the rising branch are ~35% to ~45% smaller than those anchored to the phase of maximum light. For the RVC, we used two independent reference epochs for metallic and Balmer lines and we verified that the residuals of the RVC templates anchored to the phase of mean RV are from 30% (metallic lines) up to 45% (Balmer lines) smaller than those anchored to the phase of minimum RV. We validated our RVC templates by using both the single-point and the three phase point approaches. We found that barycentric velocities based on our RVC templates are two to three times more accurate than those available in the literature. We applied the current RVC templates to Balmer lines RVs of RRLs in the globular NGC 3201 collected with MUSE at VLT. We found the cluster barycentric RV of Vγ = 496.89 ± 8.37(error) ± 3.43 (standard deviation) km s-1, which agrees well with literature estimates.

Keywords: rr lyrae variable stars; atomic spectroscopy; radial velocity; globular star clusters
The Planck Submillimeter Properties of Galactic High-mass Star-forming Regions: Dust Temperatures, Luminosities, Masses, and Star Formation Efficiency

Massive star formation occurs in the interior of giant molecular clouds and proceeds through many stages. In this work, we focus on massive young stellar objects (MYSOs) and ultracompact H II regions (UCH II), where the former are enshrouded in dense envelopes of dust and gas, the latter of which has begun dispersing. By selecting a complete sample of MYSOs and UCH II from the Red MSX Source (RMS) survey database, we combine Planck and IRAS data and build their spectral energy distributions. With these, we estimate the physical properties (dust temperatures, mass, luminosity) of the sample. Because the RMS database provides unique solar distances, it also allows the instantaneous star formation efficiency (SFE) to be investigated as a function of Galactocentric radius. We find that the SFE increases between 2 and 4.5 kpc, where it reaches a peak, likely in correspondence with the accumulation of molecular material at the end of the Galactic bar. It then stays approximately constant up to 9 kpc, after which it linearly declines, in agreement with predictions from extragalactic studies. This behavior suggests the presence of a significant amount of undetected molecular gas at RG > 8 kpc. Finally, we present diagnostic colors that can be used to identify sites of massive star formation.

Keywords: h ii regions; compact h ii region; young stellar objects; protostars
Lensing Reconstruction from the Cosmic Microwave Background Polarization with Machine Learning

The lensing effect of the cosmic microwave background (CMB) is a powerful tool for our study of the distribution of matter in the universe. The quadratic estimator (QE) method, which is widely used to reconstruct lensing potential, has been known to be suboptimal for the low noise level polarization data from next-generation CMB experiments. To improve the performance of the reconstruction, other methods, such as the maximum-likelihood estimator and machine-learning algorithms, have been developed. In this work, we present a deep convolutional neural network model named the Residual Dense Local Feature U-net (RDLFUnet) for reconstructing the CMB lensing convergence field. By simulating lensed CMB data with different noise levels to train and test network models, we find that for noise levels less than 5 μK-arcmin, RDLFUnet can recover the input gravitational potential with a higher signal-to-noise ratio than the previous deep-learning and traditional QE methods at almost the entire observation scale.

Keywords: cosmic microwave background radiation; observational cosmology; convolutional neural networks
Magnetic Field Observations in the Very Local Interstellar Medium by Voyagers 1 and 2

Observations of the magnetic field B in the very local interstellar medium (VLISM) were made by Voyager 1 (V1) in the northern hemisphere from 2012 to mid-2021 and by Voyager 2 (V2) in the southern hemisphere from 2018 through 2020. Near 2019.4, V2 observed an abrupt increase in B associated with a pressure front near the heliopause. During 2020, V2 observed an abrupt increase in B at a jump in B that was preceded by electron plasma oscillations and cosmic rays, indicating that it was a shock. The shock was followed by a decrease in B ending ~50 days later. V2 observed large-scale waves in all three components of B , before and after the shock. The largest- and intermediate-amplitude waves were in the BN and BR component, respectively, indicating that the waves were predominantly transverse several au from the heliopause. It was shown previously that waves near the heliopause were predominantly longitudinal at V1 and V2. Thus, V2 observed a mode transformation process within 10 au of the heliopause in the southern hemisphere, like that observed by V1 in the northern hemisphere. The elevation and azimuthal angles observed by V1 and V2 varied linearly with increasing distance in the VLISM. Voyager 1 observed jumps in B at two shocks and a pressure front, each followed by a decrease in B in a ramp. V1 also observed a fourth jump in B, at 2020.4, but B continued to increase until at least year 2021.5. This long-lasting increase in B was not anticipated.

Keywords: interstellar magnetic fields
Turbulence, and Proton and Electron Heating Rates in the Solar Corona: Analytical Approach

Analytical solutions for 2D and slab turbulence energies in the solar corona are presented, including a derivation of the corresponding correlation lengths, with implications for the proton and electron temperatures in the solar corona. These solutions are derived by solving the transport equations for 2D and slab turbulence energies and their correlation lengths, as well as proton and electron pressures. The solutions assume background profiles for the solar wind speed, solar wind mass density, and Alfvén velocity. Our analytical solutions can be related to those obtained from joint Parker Solar Probe and Solar Orbiter Metis coronagraph observations, as reported in Telloni et al. We find that the solution for 2D turbulence energy in the absence of nonlinear dissipation decreases more slowly compared to the dissipative solution. The solution for slab turbulence energy with no dissipation exhibits a more rapid increase compared to the dissipative solution. The proton heating rate is found to be about 82% of the total plasma heating rate at 6.3 R ⊙, which gradually decreases with increasing distance, eventually becoming ∼80% of the total plasma heating rate at ∼13 R ⊙, consistent with that found by Bandyopadhyay et al. (2023). These analytical solutions provide valuable insight for our understanding of turbulence, and its effect on proton and electron heating rates, in the solar corona. We compare the numerically solved turbulent transport equations for the 2D and slab turbulence energies, correlation lengths, and proton and electron pressures with the analytical solutions, finding good agreement between them.

Keywords: the sun; interplanetary turbulence; solar coronal heating; solar wind
A Hydro-based MCMC Analysis of SNR 0509-67.5: Revealing the Explosion Properties from Fluid Discontinuities Alone

Using Hubble Space Telescope/ACS Hα images of SNR 0509-67.5 taken ~10 yr apart, we measure the forward shock (FS) proper motions (PMs) at 231 rim locations. The average shock radius and velocity are 3.66 ± 0.036 pc and 6315 ± 310 km s-1. Hydrodynamic simulations, recast as similarity solutions, provide models for the supernova remnant's expansion into a uniform ambient medium. These are coupled to a Markov chain Monte Carlo (MCMC) analysis to determine explosion parameters, constrained by the FS measurements. For our baseline model, the MCMC posteriors yield an age of 315.5 ± 1.8 yr, a dynamical explosion center at 5h09m31.ˢ16, $-67^\circ 31^{\prime} 17\buildrel{\prime\prime}\over{.} 1$ and ambient medium densities at each azimuth ranging over 3.7-8.0 × 10-25 g cm-3. The age uncertainty can be an order of magnitude larger when considering other models, or subsets of the data. We detect stellar PMs corresponding to speeds in the Large Magellanic Cloud ≥ 770 km s-1. Five stars in the remnant show measurable PMs but none are moving radially from the dynamical center. There are four stars 1.″4 from the center, including three faint, previously unidentified ones. Using coronal [Fe XIV] λ5303 emission as a proxy for the reverse shock location, we constrain the explosion energy (for a compression factor of 4) to a value of E = (1.30 ± 0.41) × 1051 erg for the first time from shock kinematics alone. Higher compression factors (7 or more) are strongly disfavored based on multiple criteria, arguing for inefficient particle acceleration in the Balmer shocks of SNR 0509-67.5.

Keywords: supernova remnants; interstellar medium; shocks
Cloud Atlas: High-precision HST/WFC3/IR Time-resolved Observations of Directly Imaged Exoplanet HD 106906b

HD 106906b is an $\sim 11{M}_{\mathrm{Jup}}, ∼15 Myr old directly imaged exoplanet orbiting at an extremely large distance from its host star. The wide separation (7"11) between HD 106906b and its host star greatly reduces the difficulty in direct-imaging observations, making it one of the most favorable directly imaged exoplanets for detailed characterization. In this paper, we present HST/WFC3/IR time-resolved observations of HD 106906b in the F127M, F139M, and F153M bands. We have achieved ∼1% precision in the lightcurves in all three bands. The F127M lightcurve demonstrates marginally detectable (2.7σ significance) variability with a best-fitting period of 4 hr, while the lightcurves in the other two bands are consistent with flat lines. We construct primary-subtracted deep images and use these images to exclude additional companions to HD 106906 that are more massive than 4 ${M}_{\mathrm{Jup}} and locate at projected distances of more than ∼500 au. We measure the astrometry of HD 106906b in two HST/WFC3 epochs and achieve precisions better than 2.5 mas. The position angle and separation measurements do not deviate from those in the 2004 HST/ACS/HRC images for more than 1σ uncertainty. We provide the HST/WFC3 astrometric results for 25 background stars that can be used as reference sources in future precision astrometry studies. Our observations also provide the first 1.4 μm water band photometric measurement for HD 106906b. HD 106906b's spectral energy distribution and the best-fitting BT-Settl model have an inconsistency in the 1.4 μm water absorption band, which highlights the challenges in modeling atmospheres of young planetary-mass objects.

Keywords: near infrared astronomy; exoplanet atmospheres; exoplanet atmospheric variability; direct imaging; astrometry; time series analysis; hst photometry
Complex Organic Molecules Detected in 12 High-mass Star-forming Regions with Atacama Large Millimeter/submillimeter Array

Recent astrochemical models and experiments have explained that complex organic molecules (COMs; molecules composed of six or more atoms) are produced on the dust grain mantles in cold and dense gas in prestellar cores. However, the detailed chemical processes and the roles of physical conditions on chemistry are still far from understood. To address these questions, we investigated 12 high-mass star-forming regions using Atacama Large Millimeter/submillimeter Array (ALMA) Band 6 observations. They are associated with 44/95 GHz class I and 6.7 GHz class II CH3OH masers, indicative of undergoing active accretion. We found 28 hot cores with COM emission among 68 continuum peaks at 1.3 mm and specified 10 hot cores associated with 6.7 GHz class II CH3OH masers. Up to 19 COMs are identified including oxygen- and nitrogen-bearing molecules and their isotopologues in cores. The derived abundances show a good agreement with those from other low- and high-mass star-forming regions, implying that the COM chemistry is predominantly set by the ice chemistry in the prestellar core stage. One clear trend is that the COM detection rate steeply grows with the gas column density, which can be attributed to the efficient formation of COMs in dense cores. In addition, cores associated with a 6.7 GHz class II CH3OH maser tend to be enriched with COMs. Finally, our results suggest that the enhanced abundances of several molecules in our hot cores could be originated by the active accretion as well as different physical conditions of cores.

Keywords: interstellar masers; astrochemistry; interstellar molecules; massive stars; star formation; chemical abundances