adsabs/SciX_UAT_keywords huggingface dataset:
IRIS Observations of Short-term Variability in Moss Associated with Transient Hot Coronal Loops

We observed rapid variability (≲60 s) at the footpoints of transient, hot (∼8-10 MK) coronal loops in active region cores, with the Interface Region Imaging Spectrograph (IRIS). The high spatial (∼0"33) and temporal (≲5-10 s) resolution of IRIS is often crucial for the detection of this variability. We show how, in combination with 1D RADYN loop modeling, these IRIS spectral observations of the transition region (TR) and chromosphere provide powerful diagnostics of the properties of coronal heating and energy transport (thermal conduction or nonthermal electrons, NTEs). Our simulations of nanoflare-heated loops indicate that emission in the Mg II triplet can be used as a sensitive diagnostic for nonthermal particles. In our events, we observe a large variety of IRIS spectral properties (intensity, Doppler shifts, broadening, chromospheric/TR line ratios, Mg II triplet emission) even for different footpoints of the same coronal events. In several events, we find spectroscopic evidence for NTEs (e.g., TR blueshifts and Mg II triplet emission), suggesting that particle acceleration can occur even for very small magnetic reconnection events, which are generally below the detection threshold of hard X-ray instruments that provide direct detection of emission of nonthermal particles.

Keywords: solar corona; solar coronal heating; solar active regions; solar coronal loops; solar transition region; solar ultraviolet emission; solar extreme ultraviolet emission; solar energetic particles; high resolution spectroscopy; solar chromosphere
Excitation of Quasiperiodic Fast-propagating Waves in the Early Stage of the Solar Eruption

We propose a mechanism for the excitation of large-scale quasiperiodic fast-propagating magnetoacoustic (QFP) waves observed on both sides of the coronal mass ejection. Through a series of numerical experiments, we successfully simulated the quasi-static evolution of the equilibrium locations of the magnetic flux rope in response to the change of the background magnetic field, as well as the consequent loss of the equilibrium that eventually gives rise to the eruption. During the eruption, we identified QFP waves propagating radially outward of the flux rope, and tracing their origin reveals that they result from the disturbance within the flux rope. Acting as an imperfect waveguide, the flux rope allows the internal disturbance to escape to the outside successively via its surface, invoking the observed QFP waves. Furthermore, we synthesized the images of QFP waves on the basis of the data given by our simulations and found consistency with observations. This indicates that the leakage of the disturbance outside the flux rope could be a reasonable mechanism for QFP waves.

Keywords: solar coronal mass ejections; solar oscillations; solar activity; solar coronal waves; magnetohydrodynamics; shocks
Laboratory Detection of Cyanoacetic Acid: A Jet-cooled Rotational Study

Herein we present a laboratory rotational study of cyanoacetic acid (CH2(CN)C(O)OH), an organic acid as well as a -CN-bearing molecule, which is a candidate molecular system to be detected in the interstellar medium (ISM). Our investigation aims to provide direct experimental frequencies of cyanoacetic acid to guide its eventual astronomical search in low-frequency surveys. Using different jet-cooled rotational spectroscopic techniques in the time domain, we have determined a precise set of the relevant rotational spectroscopic constants, including the 14N nuclear quadrupole coupling constants for the two distinct structures, cis- and gauche-cyanoacetic acid. We believe this work will potentially allow the detection of cyanoacetic acid in the ISM, whose rotational features have remained unknown until now.

Keywords: catalogs; interstellar molecules; molecular spectroscopy; laboratory astrophysics
Imaging Lunar Craters with the Lucy Long Range Reconnaissance Imager (L'LORRI): A Resolution Test for NASA's Lucy Mission

NASA's Lucy mission is designed to better understand the unique population of Trojan asteroids. Trojans were probably captured in Jupiter's L4 and L5 points early in the solar system's evolution and little altered since then. A critical investigation of Lucy is to use its highest-resolution camera, the Lucy Long Range Reconnaissance Imager (L'LORRI), to image Trojans' surfaces to understand their geology and impact crater populations. Through crater statistics, the population of smaller bodies that produced those impacts, relative age differences across the bodies, and other comparative investigations between bodies can be studied. Mapping the crater population to the minimum diameters needed to achieve Lucy's objectives might require image subsampling and deconvolution ("processing") to improve the spatial resolution, a process whereby multiple, slightly offset images are merged to create a single, better-sampled image and deconvolved with L'LORRI's point-spread function. Lucy's first Earth Gravity Assist (EGA1) provided an opportunity to test this process's accuracy using L'LORRI images of the Moon, whose crater population is well characterized and therefore provides ground-truth testing. Specifically, the lunar crater imaging by L'LORRI during EGA1 allowed us to compare crater statistics derived from raw and processed L'LORRI images with ground-truth statistics derived from higher-resolution lunar imaging from other missions. The results indicate the processing can improve impact crater statistics such that features can be identified and measured to ≈70% the diameter that they can otherwise be reliably mapped on native L'LORRI images. This test's results will be used in the observation designs for the Lucy flyby targets.

Keywords: the moon; jupiter trojans; craters; lunar craters; astronomy image processing; observational astronomy
A New Method to Classify Type IIP/IIL Supernovae Based on Their Spectra

Type IIP and Type IIL supernovae are defined on the basis of their light curves, but the spectral criteria for distinguishing these two types of supernovae (SNe) remain unclear. We propose a spectral classification method. First, we subtract the principal components of different wavelength bands in the spectra based on the functional principal components analysis method. Then, we use support vector machine and artificial neural network to classify these two types of SNe. The best F1_Score of our classifier is 0.871 for SNe IIL, and 0.974 for SNe IIP. We found that by only using the Hα line at 6150-6800 Å for classification, the F1_Score up to 0.961 for Type IIP, and 0.818 for Type IIL SNe can be obtained. These results indicate that the profile of the Hα spectral line is the key to distinguishing the two types of SNe.

Keywords: astronomy data analysis; supernovae
Optical Constants of Ices Important to Planetary Science from Laboratory Reflectance Spectroscopy

Laboratory-derived optical constants are essential for identifying ices and measuring their relative abundances on solar system objects. Almost all optical constants of ices important to planetary science come from experiments with transmission geometries. Here we describe our new experimental setup and the modification of an iterative algorithm in the literature to measure the optical constants of ices from experiments with reflectance geometries. We apply our techniques to CH4 ice and H2O ice samples and find good agreement between our values and those in the literature, except for one CH4 band in the literature that likely suffers from saturation. The work we present here demonstrates that labs with reflectance geometries can generate optical constants essential for the proper analysis of near- and mid-infrared spectra of outer solar system objects such as those obtained with the James Webb Space Telescope.

Keywords: laboratory astrophysics; ice spectroscopy; ice composition; optical constants (ice); physical properties (ice)
A Multispecies Pseudoadiabat for Simulating Condensable-rich Exoplanet Atmospheres

Central stages in the evolution of rocky, potentially habitable planets may play out under atmospheric conditions with a large inventory of nondilute condensable components. Variations in condensate retention and accompanying changes in local lapse rate may substantially affect planetary climate and surface conditions, but there is currently no general theory to effectively describe such atmospheres. In this article, expanding on the work by Li et al., we generalize the single-component moist pseudoadiabat derivation in Pierrehumbert to allow for multiple condensing components of arbitrary diluteness and retained condensate fraction. The introduction of a freely tunable retained condensate fraction allows for a flexible, self-consistent treatment of atmospheres with nondilute condensable components. To test the pseudoadiabat's capabilities for simulating a diverse range of climates, we apply the formula to planetary atmospheres with compositions, surface pressures, and temperatures representing important stages with condensable-rich atmospheres in the evolution of terrestrial planets: a magma ocean planet in a runaway greenhouse state; a post-impact, late-veneer-analog planet with a complex atmospheric composition; and an Archean Earth-like planet near the outer edge of the classical circumstellar habitable zone. We find that variations in the retention of multiple nondilute condensable species can significantly affect the lapse rate and in turn outgoing radiation and the spectral signatures of planetary atmospheres. The presented formulation allows for a more comprehensive treatment of the climate evolution of rocky exoplanets and early Earth analogs.

Keywords: planetary atmospheres; atmospheric composition; astrobiology; exoplanet structure
One-off and Repeating Fast Radio Bursts: A Statistical Analysis

According to the number of detected bursts, fast radio bursts (FRBs) can be classified into two categories, i.e., one-off FRBs and repeating ones. We make a statistical comparison of these two categories based on the first FRB catalog of the Canadian Hydrogen Intensity Mapping Experiment Fast Radio Burst Project. Using the Anderson-Darling, Kolmogorov-Smirnov, and Energy statistic tests, we find significant statistical differences (p-value < 0.001) in the burst properties between the one-off FRBs and the repeating ones. More specifically, after controlling for distance, we find that the peak luminosities of one-off FRBs are, on average, higher than the repeating ones; the pulse temporal widths of repeating FRBs are, on average, longer than the one-off ones. The differences indicate that these two categories could have distinct physical origins. Moreover, we discuss the subpopulations of FRBs and provide statistical evidence to support the existence of subpopulations in one-off FRBs and in repeating ones.

Keywords: high energy astrophysics; radio bursts; radio transient sources
Constraining Inputs to Realistic Kilonova Simulations through Comparison to Observed r-process Abundances

Kilonovae, one source of electromagnetic emission associated with neutron star mergers, are powered by the decay of radioactive isotopes in the neutron-rich merger ejecta. Models for kilonova emission consistent with the electromagnetic counterpart to GW170817 predict characteristic abundance patterns, determined by the relative balance of different types of material in the outflow. Assuming that the observed source is prototypical, this inferred abundance pattern in turn must match r-process abundances deduced by other means, such as what is observed in the solar system. We report on analysis comparing the input mass-weighted elemental compositions adopted in our radiative transfer simulations to the mass fractions of elements in the Sun, as a practical prototype for the potentially universal abundance signature from neutron star mergers. We characterize the extent to which our parameter inference results depend on our assumed composition for the dynamical and wind ejecta and examine how the new results compare to previous work. We find that a dynamical ejecta composition calculated using the FRDM2012 nuclear mass and FRLDM fission models with extremely neutron-rich ejecta (Y e = 0.035) along with moderately neutron-rich (Y e = 0.27) wind ejecta composition yields a wind-to-dynamical mass ratio of M w /M d = 0.47, which best matches the observed AT2017gfo kilonova light curves while also producing the best-matching abundance of neutron capture elements in the solar system, though, allowing for systematics, the ratio may be as high as of order unity.

Keywords: nucleosynthesis; r-process
A Spectroscopic Method Based on the Shapes of Nuclear Deexcitation γ-Ray Lines in Solar Flares

The deexcitation γ-ray lines in solar flares result from energetic ions (e.g., protons, α-particles) interacting with the ambient nuclei in the solar atmosphere. The centroid and width of lines contain a wealth of information on the directionality, composition, and spectra of energetic ions as well as properties of the interaction sites. New calculations for the deexcitation γ-ray line shape analysis were done to study the properties of these ions. We calculate the shapes of the most intense deexcitation γ-ray lines in the solar flares, including the 12C 4.439 MeV, 16O 6.129 MeV, 24Mg 1.369 MeV, and 28Si 1.779 MeV lines, and explore the profiles of these line shapes as a function of the accelerated ion's energy spectra and composition, as well as the heliocentric angle of flare location. The merits of deexcitation γ-ray line shape analysis include (1) only a relatively small number of parameters being required in the fitting process and (2) the characteristics of accelerated ions with joint multi-line shape analysis being well constrained. We conclude that the measurement of the width and centroid of lines is an effective method for determining the properties of flare-accelerated ions.

Keywords: the sun; solar flares; solar gamma-ray emission; solar energetic particles
Chromospheric Recurrent Jets in a Sunspot Group and Their Intergranular Origin

We report on high-resolution observations of recurrent fan-like jets by the Goode Solar Telescope in multiple wavelengths inside a sunspot group. The dynamics behavior of the jets is derived from the Hα line profiles. Quantitative values for one well-identified event have been obtained, showing a maximum projected velocity of 42 km s-1 and a Doppler shift of the order of 20 km s-1. The footpoints/roots of the jets have a lifted center on the Hα line profile compared to the quiet Sun, suggesting a long-lasting heating at these locations. The magnetic field between the small sunspots in the group shows a very high resolution pattern with parasitic polarities along the intergranular lanes accompanied by high-velocity converging flows (4 km s-1) in the photosphere. Magnetic cancellations between the opposite polarities are observed in the vicinity of the footpoints of the jets. Along the intergranular lanes horizontal magnetic field around 1000 G is generated impulsively. Overall, all the kinetic features at the different layers through the photosphere and chromosphere favor a convection-driven reconnection scenario for the recurrent fan-like jets and evidence a site of reconnection between the photosphere and chromosphere corresponding to the intergranular lanes.

Keywords: solar photosphere; solar magnetic fields; solar chromosphere
Variability-selected Intermediate-mass Black Hole Candidates in Dwarf Galaxies from ZTF and WISE

While it is difficult to observe the first black hole seeds in the early universe, we can study intermediate-mass black holes (IMBHs) in local dwarf galaxies for clues about their origins. In this paper we present a sample of variability-selected active galactic nuclei (AGN) in dwarf galaxies using optical photometry from the Zwicky Transient Facility (ZTF) and forward-modeled mid-IR photometry of time-resolved Wide-field Infrared Survey Explorer (WISE) co-added images. We found that 44 out of 25,714 dwarf galaxies had optically variable AGN candidates and 148 out of 79,879 dwarf galaxies had mid-IR variable AGN candidates, corresponding to active fractions of 0.17% ± 0.03% and 0.19% ± 0.02%, respectively. We found that spectroscopic approaches to AGN identification would have missed 81% of our ZTF IMBH candidates and 69% of our WISE IMBH candidates. Only nine candidates have been detected previously in radio, X-ray, and variability searches for dwarf galaxy AGN. The ZTF and WISE dwarf galaxy AGN with broad Balmer lines have virial masses of 105 M ⊙ < M BH < 107 M ⊙, but for the rest of the sample, BH masses predicted from host galaxy mass range between 105.2 M ⊙ < M BH < 107.25 M ⊙. We found that only 5 of 152 previously reported variability-selected AGN candidates from the Palomar Transient Factory in common with our parent sample were variable in ZTF. We also determined a nuclear supernova fraction of 0.05% ± 0.01% yr-1 for dwarf galaxies in ZTF. Our ZTF and WISE IMBH candidates show the promise of variability searches for the discovery of otherwise hidden low-mass AGN.

Keywords: active galactic nuclei; intermediate-mass black holes; dwarf galaxies
Dragon's Lair: On the Large-scale Environment of BL Lac Objects

The most elusive and extreme subclass of active galactic nuclei (AGNs), known as BL Lac objects, shows features that can only be explained as the result of relativistic effects occurring in jets pointing at a small angle with respect to the line of sight. A longstanding issue is the identification of the BL Lac parent population with jets oriented at larger angles. According to the "unification scenario" of AGNs, radio galaxies with low luminosity and an edge-darkened radio morphology are the most promising candidate parent population of BL Lacs. Here we compare the large-scale environment, an orientation-independent property, of well-defined samples of BL Lacs with samples of radio galaxies all lying in the local universe. Our study reveals that BL Lacs and radio galaxies live in significantly different environments, challenging predictions of the unification scenario. We propose a solution to this problem proving that large-scale environments of BL Lacs are statistically consistent with those of compact radio sources, known as FR 0s, and share similar properties. This implies that highly relativistic jets are ubiquitous and are the natural outcome of the accretion of gas into the deep gravitational potential well produced by supermassive black holes.

Keywords: relativistic jets; astrostatistics; active galaxies; radio galaxies; galaxy clusters; bl lacertae objects
An Isotope-labeling Study of CO2 Formation Pathways in Molecular Clouds: Ultraviolet Photolysis of CO-H2O Ice

With the use of reflection-absorption infrared spectroscopy, we investigated the binary ice of CO and H2O at 10 K under ultraviolet irradiation as an analog of the interstellar ice mantle. We employed H2 18O instead of H2 16O to distinguish the formation pathways of CO2, and prepared mixed-ice samples under CO- and H2O-rich conditions as well as bilayered ice, where CO was condensed on H2O ice. After the ultraviolet irradiation onto any sample, we detected infrared absorption bands of C16O2 and C18O16O, which were generated through the CO-CO and CO-H2O reactions, respectively. The additional detection of C18O2 clearly indicated that the photodissociation and regeneration of CO2 also took place in ice. We analyzed the irradiation-time dependence of the C16O2 and C18O16O column densities in CO-rich ice to determine the effective cross sections of the CO2 formation through the CO-CO ( ${\sigma }_{{{\rm{C}}}^{16}{{\rm{O}}}_{2}}$ ) and CO-H2O ( ${\sigma }_{{{\rm{C}}}^{18}{{\rm{O}}}^{16}{\rm{O}}}$ ) reactions simultaneously: ${\sigma }_{{{\rm{C}}}^{16}{{\rm{O}}}_{2}}$ = 3 × 10-21 cm2 and ${\sigma }_{{{\rm{C}}}^{18}{{\rm{O}}}^{16}{\rm{O}}}$ = 5 × 10-18 cm2. Despite the rather small value of ${\sigma }_{{{\rm{C}}}^{16}{{\rm{O}}}_{2}}$ compared to ${\sigma }_{{{\rm{C}}}^{18}{{\rm{O}}}^{16}{\rm{O}}}$ , the former reaction was found to be nonnegligible in terms of the CO2 yield, even at the H2O-rich condition.

Keywords: molecular clouds; astrochemistry; laboratory astrophysics; interstellar dust; carbon dioxide
High-energy Emission Component, Population, and Contribution to the Extragalactic Gamma-Ray Background of Gamma-Ray-emitting Radio Galaxies

In this study, we systematically studied the X-ray to GeV gamma-ray spectra of 61 Fermi Large Area Telescope detected radio galaxies. We found an anticorrelation between peak frequency and peak luminosity in the high-energy spectral component of radio galaxies, similar to blazars. With this sample, we also constructed a gamma-ray luminosity function (GLF) of gamma-ray-loud radio galaxies. We found that blazar-like GLF shapes can reproduce their redshift and luminosity distribution, but the log N-log S relation prefers models with more low-z radio galaxies. Utilizing our latest GLF, the contribution of radio galaxies to the extragalactic gamma-ray background is found to be 1%-10%. We further investigated the nature of gamma-ray-loud radio galaxies. Compared to radio or X-ray flux-limited radio galaxy samples, the gamma-ray-selected sample tends to lack high radio power galaxies like FR II radio galaxies. We also found that only ~10% of radio galaxies are GeV gamma-ray loud. Radio galaxies may contribute to the cosmic MeV gamma-ray background comparable to blazars if gamma-ray-quiet radio galaxies have X-ray to gamma-ray spectra like Cen A, with a small gamma-ray-to-X-ray flux ratio.

Keywords: galaxy jets
Reconstructing Synoptic Maps of Solar Wind Radial Velocity between 20 and 60 R ⊙ Based on STEREO/HI1 Images

Previously, we developed a correlation-aided reconstruction method to recognize and locate solar wind transients observed by the Heliospheric Imager-1 (HI1) on board the Solar Terrestrial Relations Observatory and then developed a technique to infer the radial velocity distribution in each solar wind transient. Considering that the common field of view of HI1 may cover the full longitudes through the solar rotation, we further apply these methods to small-scale transients (STs) in a complete Carrington rotation to reconstruct a synoptic map of the solar wind radial velocity. Our test suggests that the reconstructed synoptic map is in agreement with the preset synthetic STs in latitude, longitude, and radial velocity. Then, Carrington rotation 2095 between 2010 March 26 and April 22 is selected to demonstrate the new technique. The derived synoptic map shows that the solar wind radial velocity corresponding to STs is in the range of 250-550 km s-1 between 20 and 60 R ⊙ in the low-to-middle latitudes. We extrapolate the in situ observation near 1 au to 20 R ⊙ and find that it matches the synoptic velocity map well. The magnetohydrodynamic simulations of the solar wind radial velocity are consistent with the synoptic map near the heliospheric current sheet (HCS) but usually overestimate the velocity values for STs far away from the HCS. We expect that this technique will be a powerful tool to learn about and monitor the solar wind in the inner heliosphere, where the number of human probes is limited.

Keywords: solar wind