adsabs/SciX_UAT_keywords huggingface dataset:
Results of the Photometric LSST Astronomical Time-series Classification Challenge (PLAsTiCC)

Next-generation surveys like the Legacy Survey of Space and Time (LSST) on the Vera C. Rubin Observatory (Rubin) will generate orders of magnitude more discoveries of transients and variable stars than previous surveys. To prepare for this data deluge, we developed the Photometric LSST Astronomical Time-series Classification Challenge (PLAsTiCC), a competition that aimed to catalyze the development of robust classifiers under LSST-like conditions of a nonrepresentative training set for a large photometric test set of imbalanced classes. Over 1000 teams participated in PLAsTiCC, which was hosted in the Kaggle data science competition platform between 2018 September 28 and 2018 December 17, ultimately identifying three winners in 2019 February. Participants produced classifiers employing a diverse set of machine-learning techniques including hybrid combinations and ensemble averages of a range of approaches, among them boosted decision trees, neural networks, and multilayer perceptrons. The strong performance of the top three classifiers on Type Ia supernovae and kilonovae represent a major improvement over the current state of the art within astronomy. This paper summarizes the most promising methods and evaluates their results in detail, highlighting future directions both for classifier development and simulation needs for a next-generation PLAsTiCC data set.

Keywords: astrostatistics; observational cosmology; transient detection; astronomy software
The Evolution of Compressible Solar Wind Turbulence in the Inner Heliosphere: PSP, THEMIS, and MAVEN Observations

The first computations of the compressible energy transfer rate from ~0.2 up to ~1.7 au is obtained using Parker Solar Probe (PSP), Time History of Events and Macroscale Interactions during Substorms (THEMIS), and Mars Atmosphere and Volatile EvolutioN (MAVEN) observations. Using a recently derived exact relation for isothermal magnetohydrodynamics turbulence, the compressible energy cascade rate, εC, is computed for hundred of events at different heliocentric distances, for time intervals when the spacecrafts were in the pristine solar wind. The observational results show moderate increases of εC with respect to the incompressible cascade rate, εI. Depending on the level of compressibility in the plasma, which reaches up to 25% at PSP's perihelion, the different terms in the exact compressible relation are shown to have different impacts on the total cascade rate, εC. Finally, the observational results are connected with the local ion temperature and the solar wind heating problem.

Keywords: solar wind; fast solar wind; slow solar wind; interplanetary physics
Constraints on the Physics of the Prompt Emission from Distant and Energetic Gamma-Ray Burst GRB 220101A

The emission region of γ-ray bursts (GRBs) is poorly constrained. The uncertainty on the size of the dissipation site spans over 4 orders of magnitude (1012-1017 cm) depending on the unknown energy composition of the GRB jets. The joint multiband analysis from soft X-rays to high energies (up to ~1 GeV) of one of the most energetic and distant GRBs, GRB 220101A (z = 4.618), allows us to make an accurate distinction between prompt and early afterglow emissions. The enormous amount of energy released by GRB 220101A (E iso ≈ 3 × 1054 erg) and the spectral cutoff at ${E}_{\mathrm{cutoff}}={85}_{-26}^{+16}$ MeV observed in the prompt emission spectrum constrain the parameter space of the GRB dissipation site. We put stringent constraints on the prompt emission site, requiring 700 < Γ0 < 1160 and R γ ~ 4.5 × 1013 cm. Our findings further highlight the difficulty of finding a simple self-consistent picture in the electron-synchrotron scenario, favoring instead a proton-synchrotron model, which is also consistent with the observed spectral shape. Deeper measurements of the time variability of GRBs, together with accurate high-energy observations (MeV-GeV), would unveil the nature of the prompt emission.

Keywords: gamma-ray bursts
Antisymmetric Cross-correlation between H I and CO Line Intensity Maps as a New Probe of Cosmic Reionization

Intensity mapping of the H I 21 cm line and the CO 2.61 mm line from the epoch of reionization has emerged as powerful, complementary, probes of the high-redshift universe. However, both maps and their cross-correlation are dominated by foregrounds. We propose a new analysis by which the signal is unbiased by foregrounds, i.e., it can be measured without foreground mitigation. We construct the antisymmetric part of two-point cross-correlation between intensity maps of the H I 21 cm line and the CO 2.61 mm line, arising because the statistical fluctuations of two fields have different evolution in time. We show that the sign of this new signal can distinguish model independently whether inside-out reionization happens during some interval of time. More importantly, within the framework of the excursion-set model of reionization, we demonstrate that the slope of the dipole of H I-CO cross-power spectrum at large scales is linear to the rate of change of global neutral fraction of hydrogen in a manner independent of reionization parameters, until the slope levels out near the end of reionization, but this trend might possibly depend on the framework of reionization modeling. The H I-CO dipole may be a smoking-gun probe for the speed of reionization, or "standard speedometer" for cosmic reionization. Observations of this new signal will unveil the global reionization history from the midpoint to near the completion of reionization.

Keywords: reionization; h i line emission; co line emission; line intensities; astrostatistics techniques; large-scale structure of the universe; two-point correlation function
Evidence of a Clear Atmosphere for WASP-62b: The Only Known Transiting Gas Giant in the JWST Continuous Viewing Zone

Exoplanets with cloud-free, haze-free atmospheres at the pressures probed by transmission spectroscopy represent a valuable opportunity for detailed atmospheric characterization and precise chemical abundance constraints. We present the first optical to infrared (0.3-5 μm) transmission spectrum of the hot Jupiter WASP-62b, measured with Hubble/STIS and Spitzer/IRAC. The spectrum is characterized by a 5.1σ detection of Na I absorption at 0.59 μm, in which the pressure-broadened wings of the Na D-lines are observed from space for the first time. A spectral feature at 0.4 μm is tentatively attributed to SiH at 2.1σ confidence. Our retrieval analyses are consistent with a cloud-free atmosphere without significant contamination from stellar heterogeneities. We simulate James Webb Space Telescope (JWST) observations, for a combination of instrument modes, to assess the atmospheric characterization potential of WASP-62b. We demonstrate that JWST can conclusively detect Na, H2O, FeH, NH3, CO, CO2, CH4, and SiH within the scope of its Early Release Science (ERS) program. As the only transiting giant planet currently known in the JWST Continuous Viewing Zone, WASP-62b could prove a benchmark giant exoplanet for detailed atmospheric characterization in the James Webb era.

Keywords: exoplanet atmospheres; planetary atmospheres; exoplanet atmospheric composition
The Radial Acceleration Relation in CLASH Galaxy Clusters

The radial acceleration relation (RAR) in galaxies describes a tight empirical scaling law between the total acceleration ${g}_{\mathrm{tot}}(r)={{GM}}_{\mathrm{tot}}(\lt r)/{r}^{2}$ observed in galaxies and that expected from their baryonic mass ${g}_{\mathrm{bar}}(r)={{GM}}_{\mathrm{bar}}(\lt r)/{r}^{2}$, with a characteristic acceleration scale of ${g}_{\dagger }\simeq 1.2\times {10}^{-10}$ m s-2. Here, we examine if such a correlation exists in galaxy clusters using weak-lensing, strong-lensing, and X-ray data sets available for 20 high-mass clusters targeted by the Cluster Lensing And Supernova survey with Hubble (CLASH). By combining our CLASH data with stellar mass estimates for the brightest cluster galaxies (BCGs) and accounting for the stellar baryonic component in clusters, we determine, for the first time, an RAR on BCG-cluster scales. The resulting RAR is well described by a tight power-law relation, ${g}_{\mathrm{tot}}\propto {g}_{\mathrm{bar}}^{{0.51}_{-0.05}^{+0.04}}$, with lognormal intrinsic scatter of ${14.7}_{-2.8}^{+2.9} \% $ . The slope is consistent with the low acceleration limit of the RAR in galaxies, ${g}_{\mathrm{tot}}=\sqrt{{g}_{\dagger }\,{g}_{\mathrm{bar}}}$, whereas the intercept implies a much higher acceleration scale of ${g}_{\unicode{x02021}}=(2.02\pm 0.11)\times {10}^{-9}$ m s-2, indicating that there is no universal RAR that holds on all scales from galaxies to clusters. We find that the observed RAR in CLASH clusters is consistent with predictions from a semianalytical model developed in the standard ΛCDM framework. Our results also predict the presence of a baryonic Faber-Jackson relation ( ${\sigma }_{V}^{4}\propto {M}_{\mathrm{bar}}$ ) on cluster scales.

Keywords: galaxy clusters; intracluster medium; gravitational lensing; dark matter; cosmology; x-ray astronomy
The Energy-dependent Gamma-Ray Light Curves and Spectra of the Vela Pulsar in the Dissipative Magnetospheres

We study the pulsar energy-dependent γ-ray light curves and spectra from curvature radiation in the dissipative magnetospheres. The dissipative magnetospheres with the combined force-free (FFE) and Aristotelian are computed by a pseudo-spectral method with a high-resolution simulation in the rotating coordinate system, which produces a near-FFE field structure with the dissipative region only near the equatorial current sheet outside the light cylinder. We use the test-particle trajectory method to compute the energy-dependent γ-ray light curves and phase-average and phase-resolved spectra by including both the accelerating electric field and radiation reaction. The predicted energy-dependent γ-ray light curves and spectra are then compared with those of the Vela pulsar observed by Fermi. Our results can generally reproduce the observed trends of the energy-dependent γ-ray light curves and spectra for the Vela pulsar.

Keywords: pulsars; magnetic fields; gamma-rays
Identification of Prebiotic Molecules Containing Peptide-like Bonds in a Hot Molecular Core, G10.47+0.03

After hydrogen, oxygen, and carbon, nitrogen is one of the most chemically active species in the interstellar medium. Nitrogen-bearing molecules are very important as they are actively involved in the formation of biomolecules. Therefore, it is essential to look for nitrogen-bearing species in various astrophysical sources, specifically around high-mass star-forming regions where the evolutionary history is comparatively poorly understood. In this paper, we report on the observation of three potential prebiotic molecules, namely, isocyanic acid (HNCO), formamide (NH2CHO), and methyl isocyanate (CH3NCO), which contain peptide-like bonds (-NH-C(=O)-) in a hot molecular core, G10.47 + 0.03 (hereafter, G10). Along with the identification of these three complex nitrogen-bearing species, we speculate on their spatial distribution in the source and discuss their possible formation pathways under such conditions. A rotational diagram method under local thermodynamic equilibrium has been employed to estimate the excitation temperature and the column density of the observed species. The Markov Chain Monte Carlo method was used to obtain the best-suited physical parameters of G10 as well as line properties of some species. We also determined the hydrogen column density and the optical depth for a different continuum observed in various frequency ranges. Finally, based on these observational results, we have constructed a chemical model to explain the observational findings. We found that HNCO, NH2CHO, and CH3NCO are chemically linked with each other.

Keywords: pre-biotic astrochemistry; interstellar medium; astronomy data analysis; radiative transfer simulations; chemical abundances; massive stars; high mass x-ray binary stars; protostars
Application of the Tianwen-1 DOR Signals Observed by Very Long Baseline Interferometry Radio Telescopes in the Study of Solar Wind Plasma and a Coronal Mass Ejection

The Tianwen-1 (TW1) Mars probe experienced solar conjunction for the first time in 2021. The China VLBI Network (CVN) observes the differential one-way ranging (DOR) signals of TW1 throughout its phase. This paper explores the application of CVN observation data to study the solar wind plasma. First, the frequency and phase of the DOR carrier and sidetones at each station are calculated using the Doppler method. Then, the variations in both the differential phase delays (DPD) and the total electron content (TEC) are calculated using the phase of the sidetones. We also statistically analyze the fluctuations in the Delta-DOR (ΔDOR) group delay. The results indicate that the fluctuations of the frequency, phase, ΔDOR group delay, delay rate, and TEC variations of the TW1 signals increase with the decrease of the heliocentric distance. On 2021 November 2, a coronal mass ejection (CME) passed across the ray paths of the telescope beams, when the heliocentric distance and heliographic latitude of the projected position of Mars were 30.6 Rs and 3°, respectively. Our data catch the impact of the CME on the DOR signals. The change of the DPD reaches 170 ps, which is equivalent to 986 TECU. We utilize the cross correlation to analyze the frequency fluctuations at multiple stations, and obtain the propagation direction and velocity variations of the CME. Our analysis indicates that multifrequency DOR signals observed by very long baseline interferometry stations have great application to characterize the electron density variations and propagation of the solar wind plasma.

Keywords: solar wind; solar coronal mass ejections; very long baseline interferometry; deep space probes
Short GRB Host Galaxies. I. Photometric and Spectroscopic Catalogs, Host Associations, and Galactocentric Offsets

We present a comprehensive optical and near-infrared census of the fields of 90 short gamma-ray bursts (GRBs) discovered in 2005-2021, constituting all short GRBs for which host galaxy associations are feasible (≈60% of the total Swift short GRB population). We contribute 274 new multi-band imaging observations across 58 distinct GRBs and 26 spectra of their host galaxies. Supplemented by literature and archival survey data, the catalog contains 542 photometric and 42 spectroscopic data sets. The photometric catalog reaches 3σ depths of ≳24-27 mag and ≳23-26 mag for the optical and near-infrared bands, respectively. We identify host galaxies for 84 bursts, in which the most robust associations make up 56% (50/90) of events, while only a small fraction, 6.7%, have inconclusive host associations. Based on new spectroscopy, we determine 18 host spectroscopic redshifts with a range of z ≈ 0.15-1.5 and find that ≈23%-41% of Swift short GRBs originate from z > 1. We also present the galactocentric offset catalog for 84 short GRBs. Taking into account the large range of individual measurement uncertainties, we find a median of projected offset of ≈7.7 kpc, for which the bursts with the most robust associations have a smaller median of ≈4.8 kpc. Our catalog captures more high-redshift and low-luminosity hosts, and more highly offset bursts than previously found, thereby diversifying the population of known short GRB hosts and properties. In terms of locations and host luminosities, the populations of short GRBs with and without detectable extended emission are statistically indistinguishable. This suggests that they arise from the same progenitors, or from multiple progenitors, which form and evolve in similar environments. All of the data products are available on the Broadband Repository for Investigating Gamma-Ray Burst Host Traits website.

Keywords: stellar populations; gamma-ray bursts; gravitational wave sources
Comparison of Radioastronomical Estimates of the Coronal and Solar Wind Magnetic Field with Measurements from Parker Solar Probe

The Parker Solar Probe (PSP) spacecraft is measuring plasma properties of the solar wind to heliocentric distances as small as 0.125 au or 26.9 solar radii. One of the most important plasma parameters is the strength of the magnetic field. A variety of radioastronomical remote sensing measurements also provide information on the magnetic field, from the solar surface to heliocentric distances of about 10 solar radii. In this paper, we compare radioastronomical estimates from one technique, Faraday rotation of background radio sources, with the PSP measurements. The extrapolated radioastronomical values are in good agreement with the measurements at the first and second perihelion passages in 2018 and 2019. Future radio measurements could therefore complement PSP measurements as it approaches the ultimate perihelion of 9.8 solar radii.

Keywords: solar corona; solar wind; solar magnetic fields
Activity and Rotation of Nearby Field M Dwarfs in the TESS Southern Continuous Viewing Zone

The evolution of magnetism in late-type dwarfs remains murky, as we can only weakly predict levels of activity for M dwarfs of a given mass and age. We report results from our spectroscopic survey of M dwarfs in the Southern Continuous Viewing Zone (CVZ) of the Transiting Exoplanet Survey Satellite (TESS). As the TESS CVZs overlap with those of the James Webb Space Telescope, our targets constitute a legacy sample for studies of nearby M dwarfs. For 122 stars, we obtained at least one R ≈ 2000 optical spectrum with which we measure chromospheric Hα emission, a proxy for magnetic field strength. The fraction of active stars is consistent with what is expected for field M dwarfs; as in previous studies, we find that late-type M dwarfs remain active for longer than their early-type counterparts. While the TESS light curves for ≈20% of our targets show modulations consistent with rotation, TESS systematics are not well enough understood for confident measurements of rotation periods (P rot) longer than half the length of an observing sector. We report periods for 12 stars for which we measure P rot ≲ 15 days or find confirmation for the TESS-derived P rot in the literature. Our sample of 21 P rot, which includes periods from the literature, is consistent with our targets being spun-down field stars. Finally, we examine the Hα-to-bolometric luminosity distribution for our sample. Two stars are rotating fast enough to be magnetically saturated, but are not, hinting at the possibility that fast rotators may appear inactive in Hα.

Keywords: low mass stars; stellar activity; stellar rotation
Effects of Gravitational-wave Radiation of Eccentric Neutron Star-White Dwarf Binaries on the Periodic Activity of Fast Radio Burst Sources

We revisit the eccentric neutron star (NS)-white dwarf (WD) binary model for the periodic activity of fast radio burst (FRB) sources, by including the effects of gravitational-wave (GW) radiation. In this model, the WD fills its Roche lobe at the periastron and mass transfer occurs from the WD to the NS. The accreted materials can be fragmented and arrive at the NS episodically, resulting in multiple bursts through curvature radiation. Consequently, the WD may be kicked away owing to the conservation of angular momentum. To initiate the next mass transfer, the WD has to refill its Roche lobe through GW radiation. In this scenario, whether the periodic activity can show up relies on three timescales, i.e., the orbital period P orb, the timescale T GW for the Roche lobe to be refilled, and the time span T frag for all the episodic events corresponding to each mass-transfer process. Only when the two conditions T GW ≲ P orb and T frag < P orb are both satisfied, the periodic activity will manifest itself and the period should be equal to P orb. In this spirit, the periodic activity is more likely to show up for relatively long periods (P orb ≳ several days). Thus, it is reasonable that FRBs 180916 and 121102, the only two sources having been claimed to manifest periodic activity, both correspond to relatively long periods.

Keywords: compact binary stars; white dwarf stars; neutron stars; radio transient sources
Let's Sweep: The Effect of Evolving J 2 on the Resonant Structure of a Three-planet System

Short and ultrashort period planets are peculiar types of exoplanets with periods as short as a few days or less. Although it is challenging to detect them, already several have been observed, with many additional candidates. If these planets have formation pathways similar to their longer-period counterparts, they are predicted to reside in multiplanet systems. Thus, gravitational perturbation from potential planetary neighbors may affect their orbital configuration. However, due to their close proximity to their host star, they are also subject to general relativity precession and torques from the stellar spin quadrupole moment (J 2). Here we show that an evolving J 2 due to magnetic braking affects the magnitude and location of secular resonances of the short-period planet in a multiplanet system, thus driving the short-period planet into and out of a secular resonance, exciting the planet's eccentricity and inclination. The high inclination can hinder transit observation and, in some cases, the high eccentricity may result in an unstable configuration. We propose that evolving J 2 in a multiplanet system can be critical to understanding the detectability and stability of short-period planets.

Keywords: exoplanet dynamics; exoplanet evolution; exoplanet formation; planetary system formation
Electron Reacceleration via Ion Cyclotron Waves in the Intracluster Medium

In galaxy clusters, the intracluster medium (ICM) is expected to host a diffuse, long-lived, and invisible population of "fossil" cosmic-ray electrons (CRe) with 1-100 MeV energies. These CRe, if reaccelerated by 100× in energy, can contribute synchrotron luminosity to cluster radio halos, relics, and phoenices. Reacceleration may be aided by CRe scattering upon the ion-Larmor-scale waves that spawn when ICM is compressed, dilated, or sheared. We study CRe scattering and energy gain due to ion cyclotron (IC) waves generated by continuously driven compression in 1D fully kinetic particle-in-cell simulations. We find that pitch-angle scattering of CRe by IC waves induces energy gain via magnetic pumping. In an optimal range of IC-resonant momenta, CRe may gain up to ~10%-30% of their initial energy in one compression/dilation cycle with magnetic field amplification ~3-6×, assuming adiabatic decompression without further scattering and averaging over initial pitch angle.

Keywords: intracluster medium; plasma astrophysics; cosmic rays; non-thermal radiation sources