adsabs/SciX_UAT_keywords huggingface dataset:
Properties of Short GRB Pulses in the Fourth BATSE Catalog: Implications for the Structure and Evolution of the Jetted Outflows

Considering the shortage of comparative studies on pulse temporal characteristics between single-peaked short gamma-ray bursts (sGRBs) and double-peaked sGRBs, we examine the pulse properties of a sample of 100 BATSE sGRBs using the BATSE Time-Tagged Event data with a 5 ms resolution. A total of 243 individual pulses of the single-peaked, double-peaked, and triple-peaked sGRBs are fitted to find statistical properties such as the pulse asymmetry, amplitude, peak time, and pulse width, etc. For the double-peaked sGRBs, according to the overlapping ratio between two adjacent peaks, we first define two kinds of double-peaked sGRBs as M-loose and M-tight types and find that most of the first pulses are similar to the single-peaked ones. We study the dependence of the FWHM on the photon energy among different energy bands. Interestingly, it is found that a power-law relation with an index of -0.4 does exist between the FWHM and the photon energy for the single- and double-peaked sGRBs. More interestingly, we notice that the power-law relation with a positive index also exists for several special short bursts. In view of the three typical timescales of pulses, namely the angular spreading timescale, the dynamic timescale, and the cooling timescale, we propose that the diverse power-law indexes together with the profile evolution of the GRB pulse can be used as an effective probe to diagnose the structure and evolution of the relativistically jetted outflows.

Keywords: gamma-ray bursts
Some Die Filthy Rich: The Diverse Molecular Gas Contents of Post-starburst Galaxies Probed by Dust Absorption

Quenched post-starburst galaxies (QPSBs) are a rare but important class of galaxies that show signs of rapid cessation or recent rejuvenation of star formation. A recent observation shows that about half of QPSBs have large amounts of cold gas. This molecular CO sample is, however, too small and is not without limitations. Our work aims to verify previous results by applying a new method to study a uniformly selected sample, more than 10 times larger. In particular, we present detailed analysis of Hα/Hβ ratios of face-on QPSBs at z = 0.02-0.15 and with ${M}_{\star }={10}^{10}-{10}^{11}\,{M}_{\odot }$ . We interpret the Hα/Hβ ratios by applying our recent gas mass calibration, which is based on non-PSB galaxies but predicts gas masses that are consistent with CO observations of ∼100 PSBs. We estimate the molecular gas by either using PSBs with well-measured Hα/Hβ ratios or measuring them from stacked spectra. Our analysis reveals that QPSBs have a wide range of Hα/Hβ ratios and molecular gas fractions that overlap with the typical gas fractions of star-forming or quiescent galaxies: Hα/Hβ ≈ 3-8 and ${f}_{{{\rm{H}}}_{2}}\approx 1 \% \mbox{--}20 \% $ with median ${f}_{{{\rm{H}}}_{2}}\approx 4 \% \mbox{--}6 \% $ , which correspond to ${M}_{{{\rm{H}}}_{2}}\approx (1\mbox{--}3)\times {10}^{9}\,{M}_{\odot }$ . Our results indicate that large reservoirs of cold gas are still present in significant numbers of QPSBs and that they arguably were not removed or destroyed by feedback from active galactic nuclei.

Keywords: interstellar medium; interstellar molecules; agn host galaxies; starburst galaxies; interstellar dust extinction; seyfert galaxies; galaxy evolution
Young Stellar Objects, Accretion Disks, and Their Variability with Rubin Observatory LSST

Vera C. Rubin Observatory, through the Legacy Survey of Space and Time (LSST), will allow us to derive a panchromatic view of variability in young stellar objects (YSOs) across all relevant timescales. Indeed, both short-term variability (on timescales of hours to days) and long-term variability (months to years), predominantly driven by the dynamics of accretion processes in disk-hosting YSOs, can be explored by taking advantage of the multiband filters option available in Rubin LSST, in particular the u, g, r, i filters that enable us to discriminate between photospheric stellar properties and accretion signatures. The homogeneity and depth of sky coverage that will be achieved with LSST will provide us with a unique opportunity to characterize the time evolution of disk accretion as a function of age and varying environmental conditions (e.g., field crowdedness, massive neighbors, metallicity) by targeting different star-forming regions. In this contribution to the Rubin LSST Survey Strategy Optimization Focus Issue, we discuss how implementing a dense observing cadence to explore short-term variability in YSOs represents a key complementary effort to the Wide-Fast-Deep observing mode that will be used to survey the sky over the full duration of the main survey (≈10 yr). The combination of these two modes will be vital to investigate the connection between the inner-disk dynamics and longer-term eruptive variability behaviors, such as those observed on EX Lupi-type objects.

Keywords: stellar accretion disks; circumstellar disks; classical t tauri stars; light curves; low mass stars; photometry; t tauri stars; variable stars; young star clusters; young stellar objects
Molecular Outflow in the Reionization-epoch Quasar J2054-0005 Revealed by OH 119 μm Observations

Molecular outflows are expected to play a key role in galaxy evolution at high redshift. To study the impact of outflows on star formation at the epoch of reionization, we performed sensitive Atacama Large Millimeter/submillimeter Array observations of OH 119 μm toward J2054-0005, a luminous quasar at z = 6.04. The OH line is detected and exhibits a P-Cygni profile that can be fitted with a broad blueshifted absorption component, providing unambiguous evidence of an outflow, and an emission component at near-systemic velocity. The mean and terminal outflow velocities are estimated to be v out ≈ 670 and 1500 km s‑1, respectively, making the molecular outflow in this quasar one of the fastest at the epoch of reionization. The OH line is marginally spatially resolved for the first time in a quasar at z > 6, revealing that the outflow extends over the central 2 kpc region. The mass outflow rate is comparable to the star formation rate ( ${\dot{M}}_{\mathrm{out}}/\mathrm{SFR}\sim 2$ ), indicating rapid (∼107 yr) quenching of star formation. The mass outflow rate in a sample of star-forming galaxies and quasars at 4 < z < 6.4 exhibits a positive correlation with the total infrared luminosity, although the scatter is large. Owing to the high outflow velocity, a large fraction (up to ∼50%) of the outflowing molecular gas may be able to escape from the host galaxy into the intergalactic medium.

Keywords: quasars; high-redshift galaxies; galactic winds; stellar feedback
Machine Learning Applied to X-Ray Spectra: Separating Stars in Orion Nebula Cluster from Active Galactic Nuclei in CDFS

Modern X-ray telescopes have detected hundreds of thousands of X-ray sources in the universe. However, current methods to classify these sources using the X-ray data themselves suffer problems-detailed X-ray spectroscopy of individual sources is too time consuming, while hardness ratios often lack accuracy, and can be difficult to use effectively. These methods fail to use the power of X-ray CCD detectors to identify X-ray emission lines and distinguish line-dominated spectra (from chromospherically active stars, supernova remnants, etc.) from continuum-dominated ones (e.g., compact objects or active galactic nuclei, AGN). In this paper, we probe the use of artificial neural networks (ANN) in differentiating Chandra spectra of young stars in the Chandra Orion Ultradeep Project (COUP) survey from AGN in the Chandra Deep Field South (CDFS) survey. We use these surveys to generate 100,000 artificial spectra of stars and AGN, and train our ANN models to separate the two kinds of spectra. We find that our methods reach an accuracy of ~92% in classifying simulated spectra of moderate-brightness objects in typical exposures, but their performance decreases on the observed COUP and CDFS spectra (~91%), due in large part to the relatively high background of these long-exposure data sets. We also investigate the performance of our methods with changing properties of the spectra such as the net source counts, the relative contribution of background, the absorption column of the sources, etc. We conclude that these methods have substantial promise for application to large X-ray surveys.

Keywords: x-ray surveys; x-ray identification; x-ray stars; x-ray active galactic nuclei; neural networks
Oscillation Mode Variability in Evolved Compact Pulsators from Kepler Photometry. II. Comparison of Modulation Patterns between Raw and Corrected Flux

We present the second results of an ensemble and systematic survey of oscillation mode variability in compact pulsators observed with the original Kepler mission. Two types of flux calibrations, raw and corrected, collected on two hot B subdwarf stars, KIC 2438324 and KIC 11179657, are thoroughly examined with the goal of evaluating the difference in patterns when oscillation modes modulate in amplitude (AM) and frequency (FM). We concentrate on AMs and FMs occurring in seven multiplet components in each star as representative frequencies. The analysis shows that FM measurements are independent of the flux calibration we choose. However, if flux contamination by nearby stars is large, AMs may be significantly different between raw and corrected flux. In addition, AMs suffer, to some extent, from a systematic modulation pattern, which is most likely induced by instrumental effects and differs from one star to another. Our results indicate that stars with no contamination are better candidates to quantitatively compare modulation patterns with theory and should be given a higher priority for such studies, since light contamination will destroy real AM patterns.

Keywords: photometry; stellar oscillations; b subdwarf stars; pulsation modes; pulsation frequency method
Could the Local Cavity be an Irregularly Shaped Strömgren Sphere?

Extending for 50-200 pc in all directions from the Sun, the Local Cavity has been characterized as an old supernova bubble consisting of low-density million-degree plasma heated by supernova shocks. We summarize the arguments for and against this model and conclude that hydrogen in the Local Cavity is fully ionized, and the plasma near the Galactic plane is mostly warm (10,000-20,000 K) rather than hot (106 K). The brightest extreme-ultraviolet source detected in the EUVE all-sky survey is the star ϵ CMa. Its EUV radiation photoionizes the outer layers of the Local Interstellar Cloud and other nearby warm interstellar clouds despite the star's 124 pc distance. Pulsar dispersion measures indicate an electron density of 0.012 cm-3 in the Local Cavity itself. At this density the Strömgren sphere of ϵ CMa is as large as the Local Cavity. We propose that the Local Cavity is an irregularly shaped Strömgren sphere containing a small percentage of hot gas likely in many filamentary structures. We also propose that shocks from recent supernovae encountered pre-existing Strömgren sphere gas, and that the partially ionized Local Interstellar Cloud and other nearby clouds could have been formed when supernova shocks encountered regions with relatively weak magnetic fields producing compression, higher density, and recombining hydrogen. * Based on observations made with the NASA/ESA Hubble Space Telescope obtained from the Data Archive at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS AR-09525.01A. These observations are associated with programs #12475, 12596.

Keywords: diffuse x-ray background; interstellar medium; interstellar dynamics; interstellar magnetic fields; strömgren spheres; supernova remnants; ultraviolet sources
A Mildly Relativistic Outflow from the Energetic, Fast-rising Blue Optical Transient CSS161010 in a Dwarf Galaxy

We present X-ray and radio observations of the Fast Blue Optical Transient CRTS-CSS161010 J045834-081803 (CSS161010 hereafter) at t = 69-531 days. CSS161010 shows luminous X-ray (LX ∼ 5 × 1039 erg s-1) and radio (Lν ∼ 1029 erg s-1 Hz-1) emission. The radio emission peaked at ∼100 days post-transient explosion and rapidly decayed. We interpret these observations in the context of synchrotron emission from an expanding blast wave. CSS161010 launched a mildly relativistic outflow with velocity Γβc ≥ 0.55c at ∼100 days. This is faster than the non-relativistic AT 2018cow (Γβc ∼ 0.1c) and closer to ZTF18abvkwla (Γβc ≥ 0.3c at 63 days). The inferred initial kinetic energy of CSS161010 (Ek ≳ 1051 erg) is comparable to that of long gamma-ray bursts, but the ejecta mass that is coupled to the mildly relativistic outflow is significantly larger ( $\sim 0.01\mbox{--}0.1\,{M}_{\odot }$ ). This is consistent with the lack of observed γ-rays. The luminous X-rays were produced by a different emission component to the synchrotron radio emission. CSS161010 is located at ∼150 Mpc in a dwarf galaxy with stellar mass M* ∼ 107 M⊙ and specific star formation rate sSFR ∼ 0.3 Gyr-1. This mass is among the lowest inferred for host galaxies of explosive transients from massive stars. Our observations of CSS161010 are consistent with an engine-driven aspherical explosion from a rare evolutionary path of a H-rich stellar progenitor, but we cannot rule out a stellar tidal disruption event on a centrally located intermediate-mass black hole. Regardless of the physical mechanism, CSS161010 establishes the existence of a new class of rare (rate < 0.4% of the local core-collapse supernova rate) H-rich transients that can launch mildly relativistic outflows.

Keywords: supernovae; accretion; black holes; x-ray transient sources; radio transient sources
Thermonuclear 19F(p, α)16O Reaction Rate Revised and Astrophysical Implications

We have calculated the thermonuclear 19F(p, αγ)16O reaction rate in a wide temperature region of 0.001-10 GK by re-evaluating the available experimental data. Together with recently evaluated 19(p, α0)16O and 19(p, απ)16O data, we have derived a new total reaction rate of 19F(p, α)16O using a Monte Carlo technique. The present rate is larger than the NACRE recommended one by factors of 36.4, 2.3, and 1.7 at temperatures of 0.01, 0.05, and 0.1 GK, respectively. This is because we have considered the enhanced low-energy astrophysical S factors in the (p, αγ) channel, owing to the interference effect between an 11 keV resonance and the well-known 323 keV resonance. It shows that the (p, αγ) channel dominates the total rate over the entire temperature region, except for a narrow region of 0.05-0.12 GK where the (p, α0) channel dominates, contrary to the previous conclusion. We have investigated the impact of the 19F(p, α)16O reaction rate using a simple parametric model of extra mixing in low-mass AGB stars, which would lower the fluorine abundance produced and observed in these stars. However, models considering different temperature profiles and more sophisticated approaches, such as extra mixing induced by magnetic fields, are needed to verify the results of our preliminary tests. Interestingly, our new rate has a strong impact on destruction of 19F in the CNO cycle at low temperatures of 0.02-0.03 GK, and this general behavior needs to be analyzed further.

Keywords: helium burning; reaction rates; s-process; massive stars; asymptotic giant branch stars; stellar nucleosynthesis
The SSDC Role in the LICIACube Mission: Data Management and the MATISSE Tool

Light Italian Cubesat for Imaging of Asteroids (LICIACube) is an Italian mission managed by the Italian Space Agency (ASI) and part of the NASA Double Asteroid Redirection Test (DART) planetary defense mission. Its main goals are to document the effects of the DART impact on Dimorphos, the secondary member of the (65803) Didymos binary asteroid system, characterizing the shape of the target body and performing dedicated scientific investigations on it. Within this framework, the mission Science Operations Center will be managed by the Space Science Data Center (ASI-SSDC), which will have the responsibility of processing, archiving, and disseminating the data acquired by the two LICIACube onboard cameras. In order to better accomplish this task, SSDC also plans to use and modify its scientific webtool Multi-purpose Advanced Tool for Instruments for the solar system Exploration (MATISSE), making it the primary tool for the LICIACube data analysis, thanks to its advanced capabilities for searching and visualizing data, particularly useful for the irregular shapes common to several small bodies.

Keywords: asteroids
Identification and Mitigation of a Vibrational Telescope Systematic with Application to Spitzer

We observed Proxima Centauri with the Spitzer Space Telescope Infrared Array Camera five times in 2016 and 2017 to search for transits of Proxima Centauri b. Following standard analysis procedures, we found three asymmetric, transit-like events that are now understood to be vibrational systematics. This systematic is correlated with the width of the point-response function (PRF), which we measure with rotated and nonrotated-Gaussian fits with respect to the detector array. We show that the systematic can be removed with a novel application of an adaptive elliptical-aperture photometry technique, and compare the performance of this technique with fixed and variable circular-aperture photometry, using both BiLinearly Interpolated Subpixel Sensitivity (BLISS) maps and nonbinned Pixel-Level Decorrelation (PLD). With BLISS maps, elliptical photometry results in a lower standard deviation of normalized residuals, and reduced or similar correlated noise when compared to circular apertures. PLD prefers variable, circular apertures, but generally results in more correlated noise than BLISS. This vibrational effect is likely present in other telescopes and Spitzer observations, where correction could improve results. Our elliptical apertures can be applied to any photometry observations, and may be even more effective when applied to more circular PRFs than Spitzer's.

Keywords: astronomy data analysis; photometry; light curves
JWST MIRI Flight Performance: Detector Effects and Data Reduction Algorithms

The detectors in the Mid-Infrared Instrument (MIRI) of the James Webb Space Telescope (JWST) are arsenic-doped silicon impurity band conduction (Si:As IBC) devices and are direct descendants of the Spitzer IRAC long wavelength arrays (channels 3 and 4). With appropriate data processing, they can provide excellent performance. In this paper we discuss the various non-ideal behaviors of these detectors that need to be addressed to realize their potential. We have developed a set of algorithms toward this goal, building on experience with previous similar detector arrays. The MIRI-specific stage 1 pipeline algorithms, of a three stage JWST calibration pipeline, were developed using pre-flight tests on the flight detectors and flight spares and have been refined using flight data. This paper describes these algorithms, which are included in the first stage of the JWST Calibration Pipeline for the MIRI instrument.

Keywords: astronomy data reduction; astronomy software
Turbulent Gas-rich Disks at High Redshift: Bars and Bulges in a Radial Shear Flow

Recent observations of high-redshift galaxies (z ≲ 7) reveal that a substantial fraction have turbulent, gas-rich disks with well-ordered rotation and elevated levels of star formation. In some instances, disks show evidence of spiral arms, with bar-like structures. These remarkable observations have encouraged us to explore a new class of dynamically self-consistent models using our AGAMA/RAMSES hydrodynamic N-body simulation framework that mimic a plausible progenitor of the Milky Way at high redshift. We explore disk gas fractions of f gas = 0%, 20%, 40%, 60%, 80%, and 100% and track the creation of stars and metals. The high gas surface densities encourage vigorous star formation, which in turn couples with the gas to drive turbulence. We explore three distinct histories: (i) there is no ongoing accretion and the gas is used up by the star formation, (ii) the star-forming gas is replenished by cooling in the hot halo gas, and (iii) in a companion paper, we revisit these models in the presence of a strong perturbing force. At low f disk (≲0.3), where f disk is the baryon mass fraction of the disk relative to dark matter within 2.2 R disk, a bar does not form in a stellar disk; this remains true even when gas dominates the inner disk potential. For a dominant baryon disk (f disk ≳ 0.5) at all gas fractions, the turbulent gas forms a strong radial shear flow that leads to an intermittent star-forming bar within about 500 Myr; turbulent gas speeds up the formation of bars compared to gas-free models. For f gas ≲ 60%, all bars survive, but for higher gas fractions, the bar devolves into a central bulge after 1 Gyr. The star-forming bars are reminiscent of recent discoveries in high-redshift Atacama Large Millimeter/submillimeter Array observations of gaseous disks.

Keywords: spiral galaxies; galaxy evolution; disk galaxies; active galaxies; primordial galaxies; protogalaxies; starburst galaxies; post-starburst galaxies; late-type galaxies; high-redshift galaxies
The Delayed Radio Emission in the Black Hole X-Ray Binary MAXI J1348-630

We explore the coupling between the accretion flow and the jet in black hole X-ray binary MAXI J1348-630 by analyzing the X-ray and radio observations during its 2019 outburst. We measure the time delay between the radio and Comptonization fluxes with the interpolated cross-correlation function. For the first time, we find that the radio emission lags behind the X-ray Comptonization emission by about 3 days during the rising phase covering the rising hard state and the following soft state. Such a long radio delay indicates that the Comptonization emission most likely originates from the advection-dominated accretion flow rather than the jet in this source. The Comptonization luminosity L C in 0.1–100 keV and the radio luminosity L R at 5.5 GHz, after considering the radio delay of ∼3 days, follow the correlation with a slope β = 3.04 ± 0.93, which is much steeper than the previously reported β = 0.6 or 1.40 using the total luminosity in the limited band (e.g., 1–10 keV) in the literature. This highlights the necessity of considering (1) the time delay, (2) the spectral decomposition, and (3) the broad energy band, in the radio–X-ray correlation analysis. As the jet reappears during the decaying phase (covering the soft state and the following decaying hard state) and the mini-outburst, the Componization and the radio emission appear to be almost simultaneous. And, the radio-Compton correlation during the mini-outburst becomes shallow with the correlation slope β = 1.11 ± 0.15. These indicate an intrinsic difference in the accretion–jet coupling physics between the main outburst and the mini-outburst.

Keywords: astrophysical black holes; stellar mass black holes; accretion; jets
Reconstruction of Electron Vortex in Space Plasmas

Space plasmas are turbulent and maintain different types of critical points or flow nulls. Electron vortex, as one type of flow null structure, is crucial in the energy cascade in turbulent plasmas. However, due to the limited time resolution of the spacecraft observations, one can never analyze the three-dimensional properties of the electron vortex. In the present study, with the advancement of the FOTE-V method and the unprecedented high-resolution measurements from four Magnetospheric Multiscale spacecraft, we successfully identify the electron vortex and then reconstruct its three-dimensional topology of the surrounding electron flow field. The results of the reconstruction show that the configuration of the electron vortex is elliptical. Comparison between the observation and reconstruction scales of the vortex indicates the reliable reconstruction of the flow velocity. Our study sheds light on the understanding of the topology and property of the electron vortex and its relationship with kinetic-scale magnetic holes.

Keywords: plasma physics; space plasmas; plasma astrophysics