adsabs/SciX_UAT_keywords huggingface dataset:
Ultrafast Compact Binary Mergers

The duration of orbital decay induced by gravitational waves (GWs) is often the bottleneck of the evolutionary phases going from star formation to a merger. We show here that kicks imparted to the newly born compact object during the second collapse generically result in a GW merger time distribution behaving like ${dN}/d\mathrm{log}t\propto {t}^{2/7}$ at short durations, leading to ultrafast mergers. Namely, a nonnegligible fraction of neutron star binaries, formed in this way, will merge on a timescale as short as 10 Myr, and a small fraction will merge even on a timescale less than 10 kyr. The results can be applied to different types of compact binaries. We discuss here the implications for binary neutron star mergers. These include unique short gamma-ray bursts (GRBs), eccentric and misaligned mergers, r-process enrichment in the very early Universe and in highly star-forming regions, and possible radio precursors. Interestingly, we conclude that among the few hundred short GRBs detected so far, a few must have formed via this ultrafast channel.

Keywords: gravitational waves; compact binary stars; neutron stars; core-collapse supernovae; chemical abundances; gamma-ray bursts
A Broken "α-intensity" Relation Caused by the Evolving Photosphere Emission and the Nature of the Extraordinarily Bright GRB 230307A

GRB 230307A is one of the brightest gamma-ray bursts detected so far. With the excellent observation of GRB 230307A by the Fermi Gamma-ray Burst Monitor, we can reveal the details of prompt emission evolution. As found in high time-resolution spectral analysis, the early low-energy spectral indices (α) of this burst exceed the limit of synchrotron radiation (α = -2/3) and gradually decreases with the energy flux (F). A tight E p ∝ F 0.54 correlation holds within the whole duration of the burst, where E p is the spectral peak energy. Such an evolution pattern of α and E p with intensity is called "double tracking." For the α-F relation, we find a log Bayes factor ~210 in favor of a smoothly broken power-law function over a linear function in log-linear space. We call this particular α-F relation a broken "α-intensity" and interpret it as the evolution of the ratio of thermal and nonthermal components, which is also the evolution of the photosphere. GRB 230307A with a duration of ~35 s, if indeed at a redshift of z = 0.065, is likely a neutron star merger event (i.e., it is intrinsically "short"). Intriguingly, different from GRB 060614 and GRB 211211A, this long event is not composed of a hard spike followed by a soft tail, suggesting that the properties of the prompt emission light curves are not a good tracer of the astrophysical origins of the bursts. The other possibility of z = 3.87 would point toward a very peculiar nature of both GRB 230307A and its late-time thermal-like emission.

Keywords: gamma-ray bursts
Current Events at Saturn: Ring–Planet Electromagnetic Coupling

This study presents a synthesized analysis of in situ and ground-based observations to investigate electromagnetic coupling between Saturn and its rings. During the Cassini Grand Finale, the magnetometer detected gradients in the azimuthal magnetic field B ϕ connected to Saturn's B-ring on 17 out of 21 orbits. The B ϕ gradients indicate that field-aligned currents are flowing into Saturn's B-ring at ∼1.55–1.67 R S in the ring plane, preferentially in the southern hemisphere. On average, these currents are magnetically conjugate with ground-based observations of nonsolar enhancements in emissions from Saturn's ionosphere and detected contemporaneously with ring-sourced, planetward electron beams and field-aligned charged dust grain inflow from the C- and B-rings into Saturn's atmosphere. Collectively, these observations align with Voyager-era predictions of a phenomenon known as "ring rain," where charged ring material generated inward of a nominal "critical radius" is drawn into Saturn's upper atmosphere along the magnetic field. However, we show that the B-ring currents are not likely to be a direct signature of infalling field-aligned ring grains. Instead, we propose that the ring rain generation mechanism naturally results in a sharp gradient in the ionospheric Pedersen conductance at the ∼1.57–1.67 R S boundary, which, combined with a v × B electric field in the ring ionosphere, could drive the observed B-ring currents. The Pedersen conductance in the high-conductance region of the southern ring ionosphere is constrained to ∼0.07–2 S and is observed to vary within this range on week-long timescales.

Keywords: planetary magnetospheres; planetary rings; planetary ionospheres; saturn
A DG-IMEX Method for Two-moment Neutrino Transport: Nonlinear Solvers for Neutrino-Matter Coupling

Neutrino-matter interactions play an important role in core-collapse supernova (CCSN) explosions, as they contribute to both lepton number and/or four-momentum exchange between neutrinos and matter and thus act as the agent for neutrino-driven explosions. Due to the multiscale nature of neutrino transport in CCSN simulations, an implicit treatment of neutrino-matter interactions is desired, which requires solutions of coupled nonlinear systems in each step of the time integration scheme. In this paper, we design and compare nonlinear iterative solvers for implicit systems with energy-coupling neutrino-matter interactions commonly used in CCSN simulations. Specifically, we consider electron neutrinos and antineutrinos, which interact with static matter configurations through the Bruenn 85 opacity set. The implicit systems arise from the discretization of a nonrelativistic two-moment model for neutrino transport, which employs the discontinuous Galerkin (DG) method for phase-space discretization and an implicit-explicit (IMEX) time integration scheme. In the context of this DG-IMEX scheme, we propose two approaches to formulate the nonlinear systems: a coupled approach and a nested approach. For each approach, the resulting systems are solved with Anderson-accelerated fixed-point iteration and Newton's method. The performance of these four iterative solvers has been compared on relaxation problems with various degrees of collisionality, as well as proto-neutron star deleptonization problems with several matter profiles adopted from spherically symmetric CCSN simulations. Numerical results suggest that the nested Anderson-accelerated fixed-point solver is more efficient than other tested solvers for solving implicit nonlinear systems with energy-coupling neutrino-matter interactions. * This manuscript has been authored in part by UT-Battelle, LLC, under contract DE-AC05-00OR22725 with the US Department of Energy (DOE). The US government retains and the publisher, by accepting the article for publication, acknowledges that the US government retains a nonexclusive, paid-up, irrevocable, worldwide license to publish or reproduce the published form of this manuscript, or allow others to do so, for US government purposes. The DOE will provide public access to these results of federally sponsored research in accordance with the DOE Public Access Plan (http://energy.gov/downloads/doe-public-access-plan).

Keywords: computational methods; core-collapse supernovae; radiative transfer simulations; supernova neutrinos
Comparative Analysis of Type III Radio Bursts and Solar Flares: Spatial Localization and Correlation with Solar Flare Intensity

We present a comprehensive study of type III radio bursts and their association with solar flares of magnitude M1.0 and larger, as observed by four widely separated spacecraft (Parker Solar Probe, Solar Orbiter, STEREO-A, and Wind). Our main focus is the introduction and validation of two methods for localizing radio bursts using the available multispacecraft data. The first method utilizes intensity fitting with a circular Gaussian distribution, while the second method is based on the time arrival of radio bursts. We demonstrate the effectiveness of these methods through the analysis of a single type III burst event and compare their results with the traditional radio triangulation technique. Furthermore, we conduct a statistical study of 17 type III bursts associated with M- and X-class solar flares in years 2020-2022. Our findings suggest a possible correlation between solar flare intensities and longitudes, with east limb flares tending to be weaker than west limb flares. We also observe a systematic drift of radio burst longitudes toward the east, potentially explained by a poleward component of the local density gradient. Our results suggest a strong correlation between solar flare intensities and radio burst properties, enhancing our understanding of the relationship between solar flares and type III radio bursts.

Keywords: radio astronomy; radio bursts; solar flares
Spectroastrometric Survey of Protoplanetary Disks with Inner Dust Cavities

We present high-resolution spectra and spectroastrometric (SA) measurements of fundamental rovibrational CO emission from nine nearby (≲300 pc) protoplanetary disks where large inner dust cavities have been observed. The emission-line profiles and SA signals are fit with a slab disk model that allows the eccentricity of the disk and intensity of the emission to vary as power laws. Six of the sources are well fit with our model, and three of these sources show asymmetric line profiles that can be fit by adopting a nonzero eccentricity. The three other sources have components in either their line profile or SA signal that are not captured by our disk model. Two of these sources (V892 Tau and CQ Tau) have multi-epoch observations that reveal significant variability. CQ Tau and AB Aur have CO line profiles with centrally peaked components that are similar to line profiles which have been interpreted as evidence of molecular gas arising from a wide-angle disk wind. Alternatively, emission from a circumplanetary disk could also account for this component. The interpretations of these results can be clarified in the future with additional epochs that will test the variability timescale of these SA signals. We discuss the utility of using high-resolution spectroscopy for probing the dynamics of gas in the disk and the scenarios that can give rise to profiles that are not fit with a simple disk model.

Keywords: protoplanetary disks; planetary system formation; planet formation; circumstellar disks; pre-main sequence stars
BICEP/Keck XV: The BICEP3 Cosmic Microwave Background Polarimeter and the First Three-year Data Set

We report on the design and performance of the BICEP3 instrument and its first three-year data set collected from 2016 to 2018. BICEP3 is a 52 cm aperture refracting telescope designed to observe the polarization of the cosmic microwave background (CMB) on degree angular scales at 95 GHz. It started science observation at the South Pole in 2016 with 2400 antenna-coupled transition-edge sensor bolometers. The receiver first demonstrated new technologies such as large-diameter alumina optics, Zotefoam infrared filters, and flux-activated SQUIDs, allowing ~10× higher optical throughput compared to the Keck design. BICEP3 achieved instrument noise equivalent temperatures of 9.2, 6.8, and 7.1 $\mu {{\rm{K}}}_{{\rm\small{CMB}}}\sqrt{{\rm{s}}}$ and reached Stokes Q and U map depths of 5.9, 4.4, and 4.4 μK arcmin in 2016, 2017, and 2018, respectively. The combined three-year data set achieved a polarization map depth of 2.8 μK arcmin over an effective area of 585 square degrees, which is the deepest CMB polarization map made to date at 95 GHz.

Keywords: cosmic microwave background radiation; polarimeters; gravitational waves; cosmic inflation
A Simulation-based Method for Correcting Mode Coupling in CMB Angular Power Spectra

Modern cosmic microwave background (CMB) analysis pipelines regularly employ complex time-domain filters, beam models, masking, and other techniques during the production of sky maps and their corresponding angular power spectra. However, these processes can generate couplings between multipoles from the same spectrum and from different spectra, in addition to the typical power attenuation. Within the context of pseudo-C ℓ based, MASTER-style analyses, the net effect of the time-domain filtering is commonly approximated by a multiplicative transfer function, F ℓ , that can fail to capture mode mixing and is dependent on the spectrum of the signal. To address these shortcomings, we have developed a simulation-based spectral correction approach that constructs a two-dimensional transfer matrix, ${J}_{{\ell }{\ell }^{\prime} }$ , which contains information about mode mixing in addition to mode attenuation. We demonstrate the application of this approach on data from the first flight of the SPIDER balloon-borne CMB experiment.

Keywords: cosmic microwave background radiation; observational cosmology; astronomy data analysis
Magnetar Engines in Fast Blue Optical Transients and Their Connections with SLSNe, SNe Ic-BL, and lGRBs

We fit the multiband lightcurves of 40 fast blue optical transients (FBOTs) with the magnetar engine model. The mass of the FBOT ejecta, the initial spin period, and the polar magnetic field of the FBOT magnetars are respectively constrained to ${M}_{\mathrm{ej}}={0.11}_{-0.09}^{+0.22}\,{M}_{\odot }$ , ${P}_{{\rm{i}}}={9.1}_{-4.4}^{+9.3}\,\mathrm{ms}$ , and ${B}_{{\rm{p}}}={11}_{-7}^{+18}\times {10}^{14}\,{\rm{G}}$ . The wide distribution of the value of B p spreads the parameter ranges of the magnetars from superluminous supernovae (SLSNe) to broad-line Type Ic supernovae (SNe Ic-BL; some are observed to be associated with long-duration gamma-ray bursts), which are also suggested to be driven by magnetars. Combining FBOTs with the other transients, we find a strong universal anticorrelation of ${P}_{{\rm{i}}}\propto {M}_{\mathrm{ej}}^{-0.41}$ , indicating they could share a common origin. To be specific, it is suspected that all of these transients originate from the collapse of extremely stripped stars in close binary systems, but with different progenitor masses. As a result, FBOTs distinguish themselves by their small ejecta masses with an upper limit of ~1 M ⊙, which leads to an observational separation in the rise time of the lightcurves of ~10 days. In addition, FBOTs together with SLSNe can be separated from SNe Ic-BL by an empirical line in the M peak-t rise plane corresponding to an energy requirement of the mass of 56Ni of ~0.3M ej, where M peak is the peak absolute magnitude of the transients and t rise is the rise time.

Keywords: light curves; supernovae; magnetars
Herbig-Haro Outflows in Circinus W

We report the discovery of new Herbig-Haro (HH) outflows in the Western Circinus molecular cloud. They were found using a color-composite imaging method that reveals faint Hα emission in complex environments. Follow-up observations in [S II] confirmed their classification as HH objects. Nearly half of the newly discovered objects are part of the HH 76 outflow and are associated with a likely young stellar object (YSO) candidate. We also identify the source of a second outflow. Three newly discovered objects are part of a third outflow whose origin is unknown. Four more HH objects are also discovered, each of which has a location and morphology that does not suggest an origin. In total there must be at least five YSOs in the field currently producing outflows. The discovery of new HH objects and associated driving sources in this cloud complex provides more evidence for active star formation and a relatively young age in this seldom-studied region.

Keywords: herbig-haro objects
Radial Velocities in the Fields of RR Lyr Variables NO Cas, NR Lyr, and V1176 Sgr

We report 14 radial velocities for three field stars located near the RR Lyrae variables NO Cas, NR Lyr, and V1176 Sgr. We identified the three field stars using Gaia Early Data Release 3. Two of these stars confirm the Gaia radial velocities. The third has no previously published radial velocity.

Keywords: rr lyrae variable stars
CHAOS. VI. Direct Abundances in NGC 2403

We report the direct abundances for the galaxy NGC 2403 as observed by the CHemical Abundances Of Spirals (CHAOS) project. Using the Multi-Object Double Spectrograph on the Large Binocular Telescope, we observe two fields with H II regions that cover an Rg/Re range of 0.18-2.31. Thirty-two H II regions contain at least one auroral line detection, and we detect a total of 122 temperature-sensitive auroral lines. Here, for the first time, we use the intrinsic scatter in the Te-Te diagrams, added in quadrature to the uncertainty on the measured temperature, to determine the uncertainty on an electron temperature inferred for one ionization zone from a measurement in a different ionization zone. We then use all available temperature data within a H II region to obtain a weighted-average temperature within each ionization zone. We rederive the oxygen abundances of all CHAOS galaxies using this new temperature prioritization method, and we find that the gradients are consistent with the results of a recent study of Berg et al. For NGC 2403, we measure a direct oxygen abundance gradient of -0.09(±0.03) dex/Re, with an intrinsic dispersion of 0.037(±0.017) dex and a N/O abundance gradient of -0.17(±0.03) dex/Re with an intrinsic dispersion of 0.060(±0.018) dex. For direct comparison, we use the line intensities from an earlier study of NGC 2403 by Berg et al. and find their recomputed values for the O/H and N/O gradients are consistent with ours.

Keywords: chemical abundances; spiral galaxies; galaxy evolution; interstellar medium; h ii regions
White Dwarf Binaries across the H-R Diagram

We created the APOGEE-GALEX-Gaia catalog to study white dwarf (WD) binaries. This database aims to create a minimally biased sample of WD binary systems identified from a combination of GALEX, Gaia, and APOGEE data to increase the number of WD binaries with orbital parameters and chemical compositions. We identify 3414 sources as WD binary candidates, with nondegenerate companions of spectral types between F and M, including main-sequence stars, main-sequence binaries, subgiants, sub-subgiants, red giants, and red clump stars. Among our findings are (a) a total of 1806 systems having inferred WD radii R < 25 R ⊕, which constitute a more reliable group of WD binary candidates within the main sample; (b) a difference in the metallicity distribution function between WD binary candidates and the control sample of most luminous giants (M H < -3.0); (c) the existence of a population of sub-subgiants with WD companions; (d) evidence for shorter periods in binaries that contain WDs compared to those that do not, as shown by the cumulative distributions of APOGEE radial velocity shifts; (e) evidence for systemic orbital evolution in a sample of 252 WD binaries with orbital periods, based on differences in the period distribution between systems with red clump, main-sequence binary, and sub-subgiant companions and systems with main-sequence or red giant companions; and (f) evidence for chemical enrichment during common envelope (CE) evolution, shown by lower metallicities in wide WD binary candidates (P > 100 days) compared to post-CE (P < 100 days) WD binary candidates.

Keywords: white dwarf stars; surveys; binary stars
Properties of the Prompt Optical Counterpart Arising from the Cooling of Electrons in Gamma-Ray Bursts

This work extends a contemporaneous effort to study the properties of the lower-energy counterpart synchrotron emission produced by the cooling of relativistic gamma-ray burst (GRB) electrons through radiation (synchrotron and self-Compton) emission and adiabatic losses. We derive the major characteristics (pulse duration, lag time after burst, and brightness relative to the burst) of the prompt optical counterpart (POC) occurring during or after the GRB. Depending on the magnetic field lifetime, duration of electron injection, and electron transit time Δt o from hard X-ray (GRB) to optical-emitting energies, a POC may appear during the GRB pulse (of duration δ t γ ) or after (delayed OC). The signature of counterparts arising from the cooling of GRB electrons is that POC pulses (Δt o < δ t γ ) last as long as the corresponding GRB pulse (δ t o ≃ δ t γ ), while delayed OC pulses (Δt o > δ t γ ) last as long as the transit time (δ t o ≃ Δt o ). If OC variability can be measured, then another signature for this OC mechanism is that the GRB variability is passed on to POCs but not to delayed OCs. Within the GRB electron cooling model for counterparts, POCs should be on average dimmer than delayed ones (consistent with the data), and harder GRB low-energy slopes β LE should be associated more often with the dimmer POCs. The latter sets an observational bias against detecting POCs from (the cooling of electrons in) GRBs with a hard slope β LE, making it more likely that the detected POCs of such bursts arise from another mechanism.

Keywords: non-thermal radiation sources; gamma-ray bursts; radiative processes; plasma astrophysics
Ice Inheritance in Dynamical Disk Models

The compositions of planet-forming disks are set by a combination of material inherited from the interstellar medium and material reprocessed during disk formation and evolution. Indeed, comets and primitive meteorites exhibit interstellar-like isotopic ratios and/or volatile compositions, supporting that some pristine material was incorporated intact into icy planetesimals in the solar nebula. To date, the survival of volatile interstellar material in the disk stage has not been modeled using realistic disk physics. Here, we present a modeling framework to track the destruction of interstellar ices on dust grains undergoing transport processes within a disk, with a particular focus on explaining the incorporation of pristine material into icy planetesimals. We find that it is difficult to explain inheritance through the local assembly of comets, as ice destruction is rapid for small (<10 μm) grains in the inner few tens of au. Instead, a plausible pathway to inheritance is to form pebbles at larger disk radii, which then drift inward to the comet-forming zone with their ices mostly preserved. Small grains beyond ~100 au can experience ice photodissociation at the tens of percent level; however, little of the ice is actually lost from the grain, likely making this a robust site for in situ ice chemistry. Our models also indicate that many complex organic species should survive passage through the disk intact. This raises the possibility that organics synthesized in the interstellar medium can be delivered to terrestrial planets by icy-body impact and thus potentially participate in origins of life chemistry.

Keywords: astrochemistry; protoplanetary disks; comet origins
Transverse Loop Oscillations via Vortex Shedding: A Self-oscillating Process

Identifying the underlying mechanisms behind the excitation of transverse oscillations in coronal loops is essential for their role as diagnostic tools in coronal seismology and their potential use as wave heating mechanisms of the solar corona. In this paper, we explore the concept of these transverse oscillations being excited through a self-sustaining process, caused by Alfvénic vortex shedding from strong background flows interacting with coronal loops. We show for the first time in 3D simulations that vortex shedding can generate transverse oscillations in coronal loops, in the direction perpendicular to the flow due to periodic "pushing" by the vortices. By plotting the power spectral density we identify the excited frequencies of these oscillations. We see that these frequencies are dependent both on the speed of the flow, as well as the characteristics of the oscillating loop. This, in addition to the fact that the background flow is constant and not periodic, makes us treat this as a self-oscillating process. Finally, the amplitudes of the excited oscillations are near constant in amplitude, and are comparable with the observations of decay-less oscillations. This makes the mechanism under consideration a possible interpretation of these undamped waves in coronal loops.

Keywords: solar coronal loops; solar coronal seismology