adsabs/SciX_UAT_keywords huggingface dataset:
Modeling the Multiband Light Curves of the Afterglows of Three Gamma-Ray Bursts and their Associated Supernovae

Some dozen supernovae (SNe) associated with long gamma-ray bursts (GRBs) have been confirmed. Most of the previous studies derive the physical properties of the GRB-SNe by fitting the constructed (pseudo-)bolometric light curves. However, many GRB-SNe only have a few filter data, for which the (pseudo-)bolometric light curves are very difficult to construct. Additionally, constructing (pseudo-)bolometric light curves rely on some assumptions. In this paper, we use the multiband broken power-law plus 56Ni model to fit the multiband light curves of the afterglows and the SNe (SN 2001ke, SN 2013dx, and SN 2016jca) associated with three GRBs (GRB 011121, GRB 130702A, and GRB 161219B). We find our model can account for the multiband light curves of the three GRB-SNe (except for the late-time z-band light curve of two events), indicating that the model is a reliable model. The 56Ni masses we derive are higher than those in the literature. This might be due to the fact that the 56Ni masses in the literature are usually obtained by fitting the pseudo-bolometric light curves whose luminosities are usually (significantly) underestimated. We suggest that the multiband model can not only be used to fit the multiband light curves of GRB-SNe that have many filter observations, but also fit those having sparse data.

Keywords: type ic supernovae; gamma-ray bursts
Multiple Explanations for the Single Transit of KIC 5951458 Based on Radial Velocity Measurements Extracted with a Novel Matched-template Technique

Planetary systems that show single-transit events are a critical pathway to increasing the yield of long-period exoplanets from transit surveys. From the primary Kepler mission, KIC 5951458 b (Kepler-456b) was thought to be a single-transit giant planet with an orbital period of 1310 days. However, radial velocity (RV) observations of KIC 5951458 from the HIRES instrument on the Keck telescope suggest that the system is far more complicated. To extract precise RVs for this $V\approx 13$ star, we develop a novel matched-template technique that takes advantage of a broad library of template spectra acquired with HIRES. We validate this technique and measure its noise floor to be 4-8 m s-1 (in addition to internal RV error) for most stars that would be targeted for precision RVs. For KIC 5951458, we detect a long-term RV trend that suggests the existence of a stellar companion with an orbital period greater than a few thousand days. We also detect an additional signal in the RVs that is possibly caused by a planetary or brown dwarf companion with mass in the range of 0.6-82 MJup and orbital period below a few thousand days. Curiously, from just the data on hand, it is not possible to determine which object caused the single "transit" event. We demonstrate how a modest set of RVs allows us to update the properties of this unusual system and predict the optimal timing for future observations. ∗ Some of the data presented herein were obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation.

Keywords: exoplanet astronomy; exoplanet detection methods; radial velocity; exoplanet systems
An In Situ Interplanetary "U-burst": Observation and Results

We report and examine the observation of an unusual and rare in situ electron observation associated with a solar type III radio burst on 1996 December 24. This radio event was accompanied by high-energy electrons, measured by the Solid State Telescope on board the Wind spacecraft. The type III radio emission started at ≈13:10 UTC and was associated with a C2.1 GOES-class flare whose maximum was at 13:11 UTC and hosted by the active region NOAA 8007/8004, located on the west limb at N05° W74°/N06° W85°. During this event, the observation of an electron energy distribution likely to be associated with the radio emission was registered. The electrons arrive at the spacecraft predominantly from the antisolar direction, suggesting that their general motion is sunward along a closed magnetic field line. Leblanc et al. propose a model in which energetic electrons are injected into a coronal flux tube at one of its footpoints, releasing standard type-III emission. As the magnetic field then directs them back toward the magnetic-conjugate footpoint of the first, the electrons release subsequent emission whose radio profile is a quasi-time reversal of the standard. We have constructed a cylindrical flux rope facsimile of this scenario that reproduces the U-burst profiles. We also report observational features indicating a secondary electron energy distribution and propose a scenario that explains this feature.

Keywords: solar coronal mass ejections
SImMER: A Pipeline for Reducing and Analyzing Images of Stars

We present the first public version of SImMER, an open-source Python reduction pipeline for astronomical images of point sources. Current capabilities include dark-subtraction, flat-fielding, sky-subtraction, image registration, FWHM measurement, contrast curve calculation, and table and plot generation. SImMER supports observations taken with the ShARCS camera on the Shane 3 m telescope and the PHARO camera on the Hale 5.1 m telescope. The modular nature of SImMER allows users to extend the pipeline to accommodate additional instruments with relative ease. One of the core functions of the pipeline is its image registration module, which is flexible enough to reduce saturated images and images of similar-brightness, resolved stellar binaries. Furthermore, SImMER can compute contrast curves for reduced images and produce publication-ready plots. The code is developed online at https://github.com/arjunsavel/SImMER and is both pip- and conda-installable. We develop tutorials and documentation alongside the code and host them online. With SImMER, we aim to provide a community resource for accurate and reliable data reduction and analysis.

Keywords: astronomy data analysis; astronomy data reduction; photometry
GRMHD Evolution of Interacting Double Accretion Tori Orbiting a Central Black Hole

The matter orbiting black holes (BHs) in microquasars or active galactic nuclei forms toroidal accretion disk structures, and multiple torus structures have been recently described as ringed accretion disks (RADs) in a full general relativistic approach. Here we realize full general relativistic magnetohydrodynamic (GRMHD) numerical simulations related to double toroidal structure immersed in the equatorial plane of the gravitomagnetic field of a central Schwarzschild BH in an asymptotically uniform magnetic field. We study the merging dynamics of an initial RAD structure constructed by two corotating or counterrotating tori, where accretion of matter from the outer torus is assumed onto the inner torus, using the 2.5D GRMHD simulation schemes with the HARM numerical code. We study the dynamics of the system assuming various initial conditions, and we have demonstrated that the initial matter density is the relevant factor governing the system evolution.

Keywords: black hole physics
Potential Backup Targets for Comet Interceptor

Comet Interceptor is an ESA F-class mission expected to launch in 2028 on the same launcher as ESA's ARIEL mission. Comet Interceptor's science payload consists of three spacecraft, a primary spacecraft that will carry two smaller probes to be released at the target. The three spacecraft will fly-by the target along different chords, providing multiple simultaneous perspectives of the comet nucleus and its environment. Each of the spacecraft will be equipped with different but complementary instrument suites designed to study the far and near coma environment and surface of a comet or interstellar object (ISO). The primary spacecraft will perform a fly-by at ~1000 km from the target. The two smaller probes will travel deeper into the coma, closer to the nucleus. The mission is being designed and launched without a specific comet designated as its main target. Comet Interceptor will travel to the Sun-Earth L2 Lagrangian point with ARIEL and wait in hibernation until a suitable long-period comet (LPC) is found that will come close enough to the Sun for the spacecraft to maneuver to an encounter trajectory. To prepare for all eventualities, the science team has assembled a preliminary set of backup targets from the known Jupiter family comets, where a suitable fly-by trajectory can be achieved during the nominal mission timeline (including the possibility of some launch delay). To better prioritize this list, we are releasing our potential backup targets in order to solicit the planetary community's help with observations of these objects over future apparitions and to encourage publication of archival data on these objects.

Keywords: small solar system bodies; short period comets; comets; antarctic observatories
Free Energy Sources in Current Sheets Formed in Collisionless Plasma Turbulence

Collisionless dissipation of macroscopic energy into heat is an unsolved problem of space and astrophysical plasmas, e.g., solar wind and Earth's magnetosheath. The most viable process under consideration is the turbulent cascade of macroscopic energy to kinetic scales where collisionless plasma processes dissipate the energy. Space observations and numerical simulations show the formation of kinetic scale current sheets in turbulent plasmas. Instabilities in these current sheets (CS) can provide collisionless dissipation and influence the turbulence. Spatial gradients of physical quantities and non-Maxwellian velocity distribution functions provide the free energy sources for CS plasma instabilities. To determine the free energy sources provided by the spatial gradients of plasma density and electron/ion bulk velocities in CS formed in collisionless turbulent plasmas with an external magnetic field B0, we carried out two-dimensional particle-in-cell-hybrid simulations and interpret the results within the limitations of the simulation model. We found that ion-scale CS in a collisionless turbulent plasma are formed primarily by electron shear flows, i.e., electron bulk velocity inside CS is much larger than ion bulk velocity while the density variations through the CS are relatively small (<10%). The electron bulk velocity and, thus, the current density inside the sheets are directed mainly parallel to B0. The shear in the perpendicular electron and ion bulk velocities generates parallel electron and ion flow vorticities. Inside CS, parallel electron flow vorticity exceeds the parallel ion flow vorticity, changes sign around the CS centers, and peaks near the CS edges. An ion temperature anisotropy develops near CS during the CS formation. It has a positive correlation with the parallel ion and electron flow vorticities. Theoretical estimates support the simulation results.

Keywords: space plasmas; solar wind
Peripheral Collisions of Ice-covered Silica Dust Grains

Collisions with ice-covered silica grains are studied using molecular-dynamics simulation, with a focus on the influence of the impact parameter on the collision dynamics. The ice mantle induces an attractive interaction between the colliding grains, which is caused by the melting of the mantles in the collision zone and their fusion. For noncentral collisions, this attractive interaction leads to a deflection of the grain trajectories and, at smaller velocities, to the agglomeration ("sticking") of the colliding grains. The bouncing velocity, which is defined as the smallest velocity at which grains bounce off each other rather than stick, shows only a negligible dependence on the impact parameter. Close to the bouncing velocity, a temporary bridge builds up between the colliding grains, which, however, ruptures when the collided grains separate and relaxes to the grains. At higher velocities, the ice in the collision zone is squeezed out from between the silica cores, forming an expanding disk, which ultimately tears and dissolves into a multitude of small droplets. An essential fraction of the ice cover in the collision zone is then set free to space. Astrophysical implications include the possibility that organic species that might be present in small concentrations on the ice surface or at the ice-silica interface are liberated to space in such noncentral collisions.

Keywords: circumstellar dust; astrophysical dust processes; interplanetary dust
A Pixon-based Method for Reverberation-mapping Analysis in Active Galactic Nuclei

We present an alternative method for reconstructing a velocity-delay map in reverberation mapping (RM) based on the pixon algorithm initially proposed for image reconstruction by Pina. The pixon algorithm allows for a variable pixon basis to adjust resolution of each image pixel according to the information content in that pixel, which therefore enables the algorithm to make the best possible use of measured data. The final optimal pixon basis functions would be those that minimize the number of pixons while still providing acceptable descriptions to data within the accuracy allowed by noises. We adapt the pixon algorithm to RM analysis and develop a generic framework to implement the algorithm. Simulation tests and comparisons with the widely used maximum entropy method demonstrate the feasibility and high performance of our pixon-based RM analysis. This paper serves as an introduction to the framework and the application to velocity-unresolved RM. An extension to velocity-resolved cases will be presented in a companion paper.

Keywords: reverberation mapping; active galactic nuclei; quasars; algorithms
Validation and Interpretation of a Three-dimensional Configuration of a Magnetic Cloud Flux Rope

One strong magnetic cloud (MC) with a magnetic field magnitude reaching ~40 nT at 1 au during 2012 June 16-17 is examined in association with a preexisting magnetic flux rope (MFR) identified on the Sun. The MC is characterized by a quasi-three-dimensional (3D) flux rope model based on in situ measurements from the Wind spacecraft. The contents of the magnetic flux and other parameters are quantified. In addition, a correlative study with the corresponding measurements of the same structure crossed by the Venus Express (VEX) spacecraft at a heliocentric distance of 0.7 au and with an angular separation of ~6° in longitude is performed to validate the MC modeling results. The spatial variation between the Wind and VEX magnetic field measurements is attributed to the 3D configuration of the structure appearing as a knotted bundle of flux. A comparison of the magnetic flux contents between the MC and the preexisting MFR on the Sun indicates that the 3D reconnection process accompanying an M1.9 flare may correspond to the magnetic reconnection between the field lines of the preexisting MFR rooted in the opposite polarity footpoints. Such a process reduces the amount of the axial magnetic flux in the erupted flux rope, by approximately 50%, in this case.

Keywords: magnetohydrodynamics; magnetic fields; solar corona; solar coronal mass ejections
Low-mass Population III Star Formation due to the HD Cooling Induced by Weak Lyman–Werner Radiation

Lyman–Werner (LW) radiation photodissociating molecular hydrogen (H2) influences the thermal and dynamical evolution of the Population III (Pop III) star-forming gas cloud. The effect of powerful LW radiation has been well investigated in the context of supermassive black hole formation in the early Universe. However, the average intensity in the early Universe is several orders of magnitude lower. For a comprehensive study, we investigate the effects of LW radiation at 18 different intensities, ranging from J LW/J 21 = 0 (no radiation) to 30 (H-cooling cloud), on the primordial star-forming gas cloud obtained from a three-dimensional cosmological simulation. The overall trend with increasing radiation intensity is a gradual increase in the gas cloud temperature, consistent with previous works. Due to the HD cooling, however, the dependence of gas cloud temperature on J LW deviates from the aforementioned increasing trend for a specific range of intensities (J LW/J 21 = 0.025–0.09). In HD-cooling clouds, the temperature remained below 200 K during 105 yr after the first formation of the high-density region, maintaining a low accretion rate. Finally, the HD-cooling clouds have only a low-mass dense core (above 108 cm‑3) with about 1–16 M ⊙, inside of which a low-mass Pop III star with ≤0.8 M ⊙ (a so-called "surviving star") could form. The upper limit of star formation efficiency ${M}_{\mathrm{core}}/{M}_{\mathrm{vir},\mathrm{gas}}$ significantly decreases from 10‑3 to 10‑5 as HD cooling becomes effective. This tendency indicates that, whereas the total gas mass in the host halo increases with the LW radiation intensity, the total Pop III stellar mass does not increase similarly.

Keywords: hydrodynamical simulations; population iii stars; star formation
Mixing of Hot Shocked Plasma with Cold Gas in Nova YZ Ret 2020

The origin of bright X-ray emission lines that appear late in a nova eruption remains largely a puzzle. We present two high-resolution X-ray grating spectra of the classical nova YZ Ret, observed 77 and 115 days post-eruption, using XMM-Newton and Chandra, respectively. Both spectra feature resolved emission lines blueshifted by v = –1500 km s‑1 and broadened by σ v = 500 km s‑1. The two spectra are well described by a collisionally ionized plasma of kT ∼ 70 eV that dimmed by a factor of ∼40 between the two exposures. The spectra also show narrow radiative recombination continua (RRCs) of C+4, C+5, and N+5, indicating the interaction of the hot ionized plasma with cold electrons of kT ∼ 2 eV. The high-n Rydberg series of C+4 is anomalously bright, allowing us to measure the electron density through continuum lowering, which is in agreement with the He-like N+5 density diagnostic of n e = (1.7 ± 0.4) × 1011 cm‑3. The high population of these high-n levels constitutes the best evidence to date of charge exchange (CX) with neutral H in an astrophysical ionized plasma. The remarkable fact that the velocity and plasma temperature are the same after 38 days, despite the high density and decreasing flux, is evidence for ongoing heating. We suggest the heating is due to a reverse shock in the nova ejecta, which forms a thin X-ray shell. The narrow RRCs and CX are attributed to direct mixing with cold gas, which overtakes the hot plasma either from the shock front or through the contact discontinuity.

Keywords: novae; spectroscopy; atomic physics; shocks; charge exchange recombination; radiative recombination; x-ray astronomy
Characterization of Exogenic Boulders on the Near-Earth Asteroid (101955) Bennu from OSIRIS-REx Color Images

A small number of anomalously bright boulders on the near-Earth rubble-pile asteroid (101955) Bennu were recently identified as eucritic material originating from asteroid (4) Vesta. Building on this discovery, we explored the global presence of exogenic boulders on Bennu. Our analysis focused on boulders larger than 1 m that show the characteristic 1 μm pyroxene absorption band in the four-color MapCam data from the OSIRIS-REx mission. We confirm the presence of exogenic boulders similar to eucrites and find that a mixture of eucrite with carbonaceous material is also a possible composition for some boulders. Some of the exogenic boulders have spectral properties similar to those of ordinary chondrite (OC) meteorites, although the laboratory spectra of these meteorites have a higher albedo than those measured on Bennu, which could be explained by either a grain size effect, the presence of impact melt, or optical mixing with carbonaceous material owing to dust coating. Our Monte Carlo simulations predict that the median amount of OC mass added to the parent body of Bennu is 0.055% and 0.037% of the volume of a 100 and 200 km diameter parent body, respectively. If Bennu was a uniformly mixed by-product of parent body and S-type projectiles, the equivalent mass of OC material would be a sphere with a diameter of 36-40 m (or a volume of 24,200-33,600 m3). The total amount of OC material in the interior of Bennu estimated from the MapCam data is slightly higher (91,000-150,000 m3).

Keywords: asteroid surfaces; carbonaceous chondrites; near infrared astronomy; meteorites; near-earth objects; impact phenomena; vesta
Inverse Compton Cooling in the Coronae of Simulated Black Hole Accretion Flows

We present a formulation for a local cooling function to be employed in the diffuse, hot corona region of 3D GRMHD simulations of accreting black holes. This new cooling function calculates the cooling rate due to inverse Compton scattering by considering the relevant microphysics in each cell in the corona and approximating the radiation energy density and Compton temperature thereby integrating over the thermal seed photon flux from the disk surface. The method either assumes the ion and electron temperatures are equal (1T) or calculates them separately (2T) using an instantaneous equilibrium approach predicated on the actual relevant rate equations (Coulomb and Compton). The method is shown to be consistent with a more detailed ray-tracing calculation where the bulk of the cooling occurs, but is substantially less costly to perform. As an example, we apply these methods to a HARM3D simulation of a 10M⊙, non-spinning black hole, accreting at nominally 1% the Eddington value. This new approach leads to radiative efficiency values ≃65% above Novikov-Thorne, with a larger fraction of total cooling in the corona as compared to simulations performed using the original target-temperature cooling function. Time-averaged post-processing reveals that the continuum spectral observations predicted from these simulations are qualitatively similar to actual X-ray binary data, especially so for the 1T approach, which yields a harder power-law component (Γ = 2.25) compared to the 2T version (Γ = 2.53).

Keywords: magnetohydrodynamical simulations; general relativity; accretion; x-ray binary stars
Spot Model for Identifications of Periods in Asynchronous Polars

We improved the discless accretion models in Wynn & King considering the effects of the changing aspect due to the white dwarf (WD) spin and the variable feeding intensity caused by the asynchronism, and set up a more general spot model that is not sensitive to the different forms of these effects and can be applied for the period analysis of the optical and X-ray light curve. The spot model can produce the power spectra compatible with the observations, and its simulations limit the ratio Pspin/Porb < 2 between the powers at the WD spin and the binary orbital frequencies, which is a strong criterion for identification of periods. Then we recognize the periods for CD Ind, BY Cam, and 1RXS J083842.1-282723. The spot model reveals a complex accretion geometry in the asynchronous polars (APs), which may indicate that the complex magnetic field causes their asynchronism. We think 1RXS J083842.1-282723 is a prepolar because of its highest asynchronism and stable light curve. Giving the unstable accretion process in APs, the period analysis of the long-term light curve will make the orbital signal prominent.

Keywords: am herculis stars; x-ray binary stars; x-ray photometry; ccd photometry