adsabs/SciX_UAT_keywords huggingface dataset:
Model-independent Constraints on Lorentz Invariance Violation: Implication from Updated Gamma-Ray Burst Observations

Astrophysical observations provide a unique opportunity to test possible signatures of Lorentz invariance violation (LIV), due to the high energies and long distances involved. In quantum theory of gravity, one may expect the modification of the dispersion relation between energy and momentum for photons, which can be probed with the time lag (the arrival time delay between light curves in different energy bands) of gamma-ray bursts (GRBs). In this paper, by using the detailed time delay measurements of GRB 160625B at different energy bands, as well as 23 time delay GRBs covering the redshift range of z = 0.168-2.5 (which were measured at different energy channels from the light curves), we propose an improved model-independent method (based on the newly compiled sample of H(z) measurements) to probe the energy-dependent velocity due to the modified dispersion relation for photons. In the framework of a more complex and reasonable theoretical expression to describe the time delays, our results imply that the intrinsic time lags can be better described with more GRB time delay data. More importantly, through direct fitting of the time delay measurements of a sample of GRBs, our limit on the LIV energy scale is comparable to that with unknown constant for the intrinsic time lag, much lower than the Planck energy scale in both linear LIV and quadratic LIV cases.

Keywords: gamma-ray bursts; gravitation; general relativity; distance indicators; particle astrophysics
The Effective Field Theory of Large-scale Structures of a Fuzzy Dark Matter Universe

Ultralight scalar fields and their noninteracting class, i.e., the so-called fuzzy dark matter (FDM), are dark matter candidates introduced to solve the small-scale problems of the standard cold dark matter. In this paper, we investigate whether the physics of FDM, particularly the quantum pressure that leads to the suppression of structure formation on small scales, could leave significant imprints on the large-scale statistics of matter fluctuations. For this purpose, we utilize the Effective Field Theory of Large Scale Structures (EFT of LSS), wherein small-scale physics is integrated and represented on large scales by only a set of free parameters. These parameters can be determined by fitting them into the cosmological simulations. By fitting the EFT predictions to the simulation data, we determine the value of the speed of sound as a quantitative measure of how UV physics affects large-scale perturbation. We use the Gadget-2 code to study the evolution of 5123 particles in a box with a side length 250 h -1 Mpc. We exploit the suppressed FDM initial power for the FDM universe and perform N-body simulation sufficient to produce accurate-enough for our purpose-results on large scales. In particular, we perform three FDM simulations with different masses and compare their sound speed with the standard cold dark matter (CDM) simulation. We found no difference between the FDM and CDM sound speeds beyond the confidence intervals. However, a consistently increasing trend can be seen in the sound speed for lower masses. This result suggests further investigations using higher-resolution simulations.

Keywords: large-scale structure of the universe; dark matter distribution; cosmology; dark matter
Electric Current Neutralization in Solar Active Regions and Its Relation to Eruptive Activity

It is well established that magnetic free energy associated with electric currents powers solar flares and coronal mass ejections (CMEs) from solar active regions (ARs). However, the conditions that determine whether an AR will produce an eruption are not well understood. Previous work suggests that the degree to which the driving electric currents, or the sum of all currents within a single magnetic polarity, are neutralized may serve as a good proxy for assessing the ability of ARs to produce eruptions. Here, we investigate the relationship between current neutralization and flare/CME production using a sample of 15 flare-active and 15 flare-quiet ARs. All flare-quiet and four flare-active ARs are also CME-quiet. We additionally test the relation of current neutralization to the degree of shear along polarity inversion lines (PILs) in an AR. We find that flare-productive ARs are more likely to exhibit non-neutralized currents, specifically those that also produce a CME. We find that flare/CME-active ARs also exhibit higher degrees of PIL shear than flare/CME-quiet ARs. We additionally observe that currents become more neutralized during magnetic flux emergence in flare-quiet ARs. Our investigation suggests that current neutralization in ARs is indicative of their eruptive potential.

Keywords: solar magnetic fields; solar corona; solar flares; solar coronal mass ejections
Differential Behaviors of Suprathermal 4He and Fe Populations in the Interplanetary Medium during Solar Cycle 24

Investigations on the solar cycle variation of the properties of suprathermal populations (H and other heavy ions like 4He, 3He, C, O, and Fe) in the solar wind are sparse and hence poorly understood. In the present investigation, solar cycle variations of "quiet" time suprathermal elements are investigated using <~ 1 MeV n-1 particle flux data obtained from the Ultra-Low Energy Isotope Spectrometer on board the Advanced Composition Explorer satellite during solar cycles 23 and 24. The analysis reveals that helium (4He) shows zero or positive lags with respect to sunspot numbers in solar cycle 23 while it shows zero or negative lag in solar cycle 24. On the contrary, although iron (Fe) shows a zero or positive lag in cycle 23 similar to 4He, it shows only a zero lag in cycle 24 and no negative lag is seen. Further, significant differences in the spectral indices are seen between 4He and Fe in cycle 24 compared to cycle 23. These results suggest that generation mechanisms responsible for suprathermal 4He and Fe underwent changes in cycle 24 and these mechanisms are probably dependent on the first ionization potential and mass-to-charge ratio. This proposition gets credence from the fact that changes in the lags and spectral slopes for C and O are not significantly different in cycles 23 and 24.

Keywords: solar energetic particles; corotating streams; solar wind; solar coronal mass ejections
Unpacking Merger Jets: A Bayesian Analysis of GW170817, GW190425 and Electromagnetic Observations of Short Gamma-Ray Bursts

We present a novel fully Bayesian analysis to constrain short gamma-ray burst (sGRB) jet structures associated with cocoon, wide-angle, and simple top-hat jet models, as well as the binary neutron star (BNS) merger rate. These constraints are made given the distance and inclination information from GW170817, observed flux of GRB 170817A, observed rate of sGRBs detected by Swift, and the neutron star merger rate inferred from LIGO's first and second observing runs. A separate analysis is conducted where a fitted sGRB luminosity function is included to provide further constraints. The jet structure models are further constrained using the observation of GW190425, and we find that the assumption that it produced a GRB 170817-like sGRB which went undetected due to the jet geometry is consistent with previous observations. We find and quantify evidence for low-luminosity and wide-angle jet structuring in the sGRB population, independently from afterglow observations, with log Bayes factors of 0.45-0.55 for such models when compared to a classical top-hat jet. Slight evidence is found for a Gaussian jet structure model over all others when the fitted luminosity function is provided, producing log Bayes factors of 0.25-0.9 ± 0.05 when compared to the other models. However, without considering GW190425 or the fitted luminosity function, the evidence favors a cocoon-like model with log Bayes factors of 0.14 ± 0.05 over the Gaussian jet structure. We provide new constraints to the BNS merger rates of 1-1300 Gpc-3 yr-1 or 2-680 Gpc-3 yr-1 when a fitted luminosity function is assumed.

Keywords: gamma-ray bursts; gravitational waves
The JCMT BISTRO-2 Survey: Magnetic Fields of the Massive DR21 Filament

We present 850 μm dust polarization observations of the massive DR21 filament from the B-fields In STar-forming Region Observations (BISTRO) survey, using the POL-2 polarimeter and the SCUBA-2 camera on the James Clerk Maxwell Telescope. We detect ordered magnetic fields perpendicular to the parsec-scale ridge of the DR21 main filament. In the subfilaments, the magnetic fields are mainly parallel to the filamentary structures and smoothly connect to the magnetic fields of the main filament. We compare the POL-2 and Planck dust polarization observations to study the magnetic field structures of the DR21 filament on 0.1-10 pc scales. The magnetic fields revealed in the Planck data are well-aligned with those of the POL-2 data, indicating a smooth variation of magnetic fields from large to small scales. The plane-of-sky magnetic field strengths derived from angular dispersion functions of dust polarization are 0.6-1.0 mG in the DR21 filament and ~0.1 mG in the surrounding ambient gas. The mass-to-flux ratios are found to be magnetically supercritical in the filament and slightly subcritical to nearly critical in the ambient gas. The alignment between column density structures and magnetic fields changes from random alignment in the low-density ambient gas probed by Planck to mostly perpendicular in the high-density main filament probed by James Clerk Maxwell Telescope. The magnetic field structures of the DR21 filament are in agreement with MHD simulations of a strongly magnetized medium, suggesting that magnetic fields play an important role in shaping the DR21 main filament and subfilaments.

Keywords: interstellar magnetic fields; star forming regions; interstellar filaments; submillimeter astronomy; polarimetry
Mapping Observations of Peptide-like Molecules around Sagittarius B2

Peptide-like molecules, which have a close connection with the origin of life, have been detected in the Universe. Mapping observations of HCONH2 and CH3CONH2, two of the simplest peptide-like molecules, are performed toward the Sagittarius B2 (Sgr B2) complex with the IRAM 30 m telescope. Seven transitions of HCONH2 and five transitions of CH3CONH2 are used in the analysis. The spatial distributions of the excitation temperature and column density of HCONH2 in the molecular envelope of Sgr B2 are obtained by rotation diagrams. Assuming the same excitation temperature of HCONH2, the column densities of CH3CONH2 are also calculated. The results show that the excitation temperature ranges from 6 to 46 K in the molecular envelope of Sgr B2. The abundance ratios between HCONH2 and CH3CONH2 are calculated to explore the relationship between them, as are those between HCONH2 and HNCO. The abundance ratio of CH3CONH2/HCONH2 varies from 10% to 20%, while that of HCONH2/HNCO ranges from 1.5% to 10%. CH3CONH2 is enhanced with respect to HCONH2 in the northwest region of Sgr B2. One transition of H13CONH2 is detected toward 12 positions of Sgr B2, from which a 12C/13C ratio of 28.7 is obtained. A time-dependent chemical model with a short-duration X-ray burst is used to explain the observed abundances of HCONH2 and CH3CONH2, with the best-fitting result at T dust = 53-56 K. More chemical reactions are required to be included in the model since the modeled abundance is lower than the observed one at the observed T dust.

Keywords: interstellar molecules; abundance ratios; isotopic abundances; molecular clouds
The Return of the Rosetta Target: Keck Near-infrared Observations of Comet 67P/Churyumov-Gerasimenko in 2021

High-resolution near-infrared ground-based spectroscopic observations of comet 67P/Churyumov-Gerasimenko near its maximum activity in 2021 were conducted from the W. M. Keck Observatory, using the facility spectrograph NIRSPEC. 67P is the best-studied comet to date because of the unprecedented detail and insights provided by the Rosetta mission during 2014-2016. Because 67P is the only comet where the detailed abundances of many coma volatiles were measured in situ, determining its composition from the ground provides a unique opportunity to interpret Rosetta results within the context of the large database of ground-based compositional measurements of comets. However, previous apparitions, including in 2015, have been unfavorable for in-depth ground-based studies of parent volatiles in 67P. The 2021 apparition of 67P was thus the first-ever opportunity for such observations. We report gas spatial distributions, rotational temperatures, production rates, and relative abundances (or stringent upper limits) among seven volatile species: C2H2, C2H6, HCN, NH3, CH3OH, H2CO, and H2O. The measured abundances of trace species relative to water reveal near average or below average values compared to previous comets studied at infrared wavelengths. Both gas rotational temperatures and the spatial distributions of H2O, C2H6, and HCN measured with Keck-NIRSPEC in 2021 are consistent with the outgassing patterns revealed by Rosetta in 2015 at very similar heliocentric distance (post-perihelion). These results can be integrated with both Rosetta mission findings and ground-based cometary studies of the overall comet population, for which we encourage a wide-scale collaboration across measurement techniques.

Keywords: solar system; small solar system bodies; comets; short period comets; comae; neutral coma gases
Effects of 150-1000 eV Electron Impacts on Pure Carbon Monoxide Ices Using the Interstellar Energetic-Process System (IEPS)

Pure CO ice has been irradiated with electrons of energy in the range 150-1000 eV with the Interstellar Energetic-Process System. The main products of irradiation are carbon chains Cn (n = 3, 5, 6, 8, 9, 10, 11, 12), suboxides, CnO (n = 2, 3, 4, 5, 6, 7), and CnO2 (n = 1, 3, 4, 5, 7) species. CO2 is by far the most abundant reaction product in all the experiments. The destruction cross section of CO peaks at about 250 eV, decreases with the energy of the electrons and is more than one order of magnitude higher than for gas-phase CO ionization. The production cross section of carbon dioxide has been also derived and is characterized by the competition between chemistry and desorption. Desorption of CO and of new species during the radiolysis follows the electron distribution in the ice. Low-energy electrons having short penetration depths induce significant desorption. Finally, as the ice thickness approaches the electron penetration depth the abundance of the products starts to saturate. Implications on the atmospheric photochemistry of cold planets hosting surface CO ices are also discussed.

Keywords: astrochemistry; protoplanetary disks; laboratory astrophysics
The Peculiar Ejecta Rings in the O-Rich Supernova Remnant Puppis A: Evidence of a Binary Interaction?

Near the center of the Puppis A supernova remnant a series of nested, optically emitting rings of high-velocity ejecta (known as "the Swirl") were identified several decades ago by Winkler et al. To date, no follow-up observations of these rings have been published, and their physical origin has remained a mystery. We present results of integral field spectroscopy of the Swirl using the Wide Field Integral Spectrograph on the 2.3 m telescope at Siding Spring Observatory in Australia. The outermost ring exhibits a nitrogen-rich spectrum blueshifted to 1350 km s-1, with smaller blueshifted rings within the first exhibiting mostly oxygen-rich spectra moving at 1000 and 750 km s-1. The structures are connected by material of intermediate velocity and variable composition, including sulfur-rich material. The Swirl is turbulent and shock-excited, and contains as much as 0.5 M ⊙ of metal-rich material. The chemical composition and exclusively blueshifted radial velocities of the Swirl are consistent with progressively deeper nucleosynthetic layers in a massive progenitor star. We suggest the possibility that the Swirl marks a "funnel" carved into the supernova ejecta by a close, massive binary companion at the moment of explosion.

Keywords: supernova remnants
L-band Integral Field Spectroscopy of the HR 8799 Planetary System

Understanding the physical processes sculpting the appearance of young gas-giant planets is complicated by degeneracies confounding effective temperature, surface gravity, cloudiness, and chemistry. To enable more detailed studies, spectroscopic observations covering a wide range of wavelengths are required. Here we present the first L-band spectroscopic observations of HR 8799 d and e and the first low-resolution wide-bandwidth L-band spectroscopic measurements of HR 8799 c. These measurements were facilitated by an upgraded LMIRCam/ALES instrument at the Large Binocular Telescope, together with a new apodizing phase plate coronagraph. Our data are generally consistent with previous photometric observations covering similar wavelengths, yet there exists some tension with narrowband photometry for HR 8799 c. With the addition of our spectra, each of the three innermost observed planets in the HR 8799 system has had its spectral energy distribution measured with integral field spectroscopy covering ~0.9-4.1 μm. We combine these spectra with measurements from the literature and fit synthetic model atmospheres. We demonstrate that the bolometric luminosity of the planets is not sensitive to the choice of model atmosphere used to interpolate between measurements and extrapolate beyond them. Combining luminosity with age and mass constraints, we show that the predictions of evolutionary models are narrowly peaked for effective temperature, surface gravity, and planetary radius. By holding these parameters at their predicted values, we show that more flexible cloud models can provide good fits to the data while being consistent with the expectations of evolutionary models.

Keywords: exoplanet detection methods; exoplanet evolution; exoplanet atmospheres
Source Region and Launch Characteristics of Magnetic-arch-blowout Solar Coronal Mass Ejections Driven by Homologous Compact-flare Blowout Jets

We study the formation of four coronal mass ejections (CMEs) originating from homologous blowout jets. All of the blowout jets originated from NOAA Active Region (AR) 11515 on 2012 July 2, within a time interval of ≈14 hr. All of the CMEs were wide (angular widths ≈ 95°–150°), and propagated with speeds ranging between ≈300 and 500 km s‑1 in LASCO coronagraph images. Observations at various EUV wavelengths in Solar Dynamics Observatory/Atmospheric Imaging Assembly images reveal that in all the cases, the source region of the jets lies at the boundary of the leading part of AR 11515 that hosts a small filament before each event. Coronal magnetic field modeling based on nonlinear force-free extrapolations indicates that in each case, the filament is contained inside of a magnetic flux rope that remains constrained by overlying compact loops. The southern footpoint of each filament is rooted in the negative polarity region where the eruption onsets occur. This negative polarity region undergoes continuous flux changes, including emergence and cancellation with opposite polarity in the vicinity of the flux rope, and the EUV images reveal brightening episodes near the filament's southeastern footpoint before each eruption. Therefore, these flux changes are likely the cause of the subsequent eruptions. These four homologous eruptions originate near adjacent feet of two large-scale loop systems connecting from that positive polarity part of the AR to two remote negative polarity regions, and result in large-scale consequences in the solar corona.

Keywords: solar coronal mass ejections; solar active regions; solar active region filaments; solar flares; solar coronal transients; solar magnetic fields
Irradiated Disks May Settle into Staircases

Much of a protoplanetary disk is thermally controlled by irradiation from the central star. Such a disk, long thought to have a smoothly flaring shape, is unstable due to the so-called irradiation instability. But what is the outcome of such an instability? In particular, is it possible that such a disk settles into a shape that is immune to the instability? We combine Athena++ with a simplified thermal treatment to show that passively heated disks settle into a staircase shape. Here, the disk is punctuated by bright rings and dark gaps, with the bright rings intercepting the lion's share of stellar illumination, and the dark gaps are hidden in their shadows. The optical surface of such a disk (the height at which starlight is absorbed) resembles a staircase. Although our simulations do not have realistic radiative transfer, we use the RADMC-3D code to show that this steady state is in good thermal equilibrium. It is possible that realistic disks reach such a state via ways not captured by our simulations. In contrast to our results here, two previous studies have claimed that irradiated disks stay smooth. We show here that they err on different issues. The staircase state, if confirmed by more sophisticated radiative hydrodynamic simulations, has a range of implications for disk evolution and planet formation.

Keywords: protoplanetary disks; circumstellar disks; radiative transfer
CO Excitation and its Connection to Star Formation at 200 pc in NGC 1365

We report high-resolution (2″ ~ 200 pc) mappings of the central region of the nearby barred spiral galaxy NGC 1365 in the CO(1-0) and CO(2-1) emission lines. The 2-1/1-0 ratio of integrated intensities shows a large scatter (0.15) with a median value of 0.67. We also calculate the ratio of velocity dispersions and peak temperatures and find that in most cases the velocity dispersion ratio is close to unity and thus the peak temperature ratio is comparable to the integrated intensity ratio. This result indicates that both CO(1-0) and CO(2-1) lines trace similar components of molecular gas, with their integrated intensity (or peak temperature) ratios reflecting the gas density and/or temperature. Similar to recent kiloparsec-scale studies, these ratios show a positive correlation with a star formation rate indicator (here we use an extinction-corrected Hα map), suggesting that molecular gas associated with recent star formation is denser and/or warmer. We also find that some CO spectra show two peaks owing to complicated kinematics, and such two components likely trace molecular gas at different conditions. This result demonstrates the importance of spectral fitting to measure integrated intensities and their ratios more accurately.

Keywords: barred spiral galaxies; co line emission; molecular gas; star formation