adsabs/SciX_UAT_keywords huggingface dataset:
A Solar Magnetic-fan Flaring Arch Heated by Nonthermal Particles and Hot Plasma from an X-Ray Jet Eruption

We have investigated an M1.3 limb flare, which develops as a magnetic loop/arch that fans out from an X-ray jet. Using Hinode/EIS, we found that the temperature increases with height to a value of over 107 K at the loop top during the flare. The measured Doppler velocity (redshifts of 100-500 km s-1) and the nonthermal velocity (≥100 km s-1) from Fe XXIV also increase with loop height. The electron density increases from 0.3 × 109 cm-3 early in the flare rise to 1.3 × 109 cm-3 after the flare peak. The 3D structure of the loop derived with Solar TErrestrial RElations Observatory/EUV Imager indicates that the strong redshift in the loop-top region is due to upflowing plasma originating from the jet. Both hard X-ray and soft X-ray emission from the Reuven Ramaty High Energy Solar Spectroscopic Imager were only seen as footpoint brightenings during the impulsive phase of the flare, then, soft X-ray emission moved to the loop top in the decay phase. Based on the temperature and density measurements and theoretical cooling models, the temperature evolution of the flare arch is consistent with impulsive heating during the jet eruption followed by conductive cooling via evaporation and minor prolonged heating in the top of the fan loop. Investigating the magnetic field topology and squashing factor map from Solar Dynamics Observatory/HMI, we conclude that the observed magnetic-fan flaring arch is mostly heated from low atmospheric reconnection accompanying the jet ejection, instead of from reconnection above the arch as expected in the standard flare model.

Keywords: solar flare spectra; solar flares; solar extreme ultraviolet emission; solar x-ray emission; spectroscopy
On the Energy Dispersion of Magnetic Rossby Waves

The energy dispersion of magnetic Rossby waves has been investigated by applying the two-dimensional incompressible magnetohydrodynamic (MHD) equations in both uniform basic flow and basic magnetic field. The dispersion relation suggests that the magnetic Rossby waves can be divided into fast- and slow-propagating modes, respectively. The fast-propagating mode propagates eastward and is similar to the fast Alfvén waves. The energy dispersion speed is faster than the phase speed, which means the perturbation energy can lead the perturbations themselves to arrive downstream. The slow-propagating waves with smaller (larger) horizontal scales are similar to those of the slow Alfvén waves (Rossby waves). The zonal group velocity is slower than the zonal phase speed for the slow-propagating magnetic Rossby waves. For the slow-propagating waves that propagate eastward, this means that the perturbation energy may trigger new perturbations that are located upstream of the perturbations themselves. The group velocity vector is basically same as (opposite of) the wavevector for the fast-propagating (slow-propagating) magnetic Rossby waves that propagate eastward. The endpoints of the group velocity vectors and the wavevector multiplying a factor are located on a cycle in the wavenumber space. Due to the uniform basic flow and the uniform basic magnetic field, the energy dispersion paths (called rays) are straight lines. Along the straight-line rays, the wave action, wave energy, and amplitude keep their initial values, and the wave neither develops nor decays.

Keywords: magnetohydrodynamics; internal waves; solar atmospheric motions; astrophysical fluid dynamics; planetary atmospheres
A Systematic View of Ten New Black Hole Spins

The launch of NuSTAR and the increasing number of binary black hole (BBH) mergers detected through gravitational wave observations have exponentially advanced our understanding of BHs. Despite the simplicity owed to being fully described by their mass and angular momentum, BHs have remained mysterious laboratories that probe the most extreme environments in the universe. While significant progress has been made in the recent decade, the distribution of spin in BHs has not yet been understood. In this work, we provide a systematic analysis of all known BHs in X-ray binary systems (XBs) that have previously been observed by NuSTAR, but have not yet had a spin measurement made using the "relativistic reflection" method obtained from those data. By looking at all the available archival NuSTAR data of these sources, we measure 10 new BH spins: IGR J17454-2919 - $a={0.97}_{-0.17}^{+0.03};$ GRS 1758-258 - $a={0.991}_{-0.019}^{+0.007};$ MAXI J1727-203 - $a={0.986}_{-0.159}^{+0.012};$ MAXI J0637-430 - a = 0.97 ± 0.02; Swift J1753.5-0127 - $a={0.997}_{-0.003}^{+0.001};$ V4641 Sgr - $a={0.86}_{-0.06}^{+0.04};$ 4U 1543-47 - $a={0.98}_{-0.02}^{+0.01};$ 4U 1957+11 - $a={0.95}_{-0.04}^{+0.02};$ H 1743-322 - $a={0.98}_{-0.02}^{+0.01};$ and MAXI J1820+070 - $a={0.988}_{-0.028}^{+0.006}$ (all uncertainties are at the 1σ confidence level). We discuss the implications of our measurements on the entire distribution of stellar-mass BH spins in XBs, and we compare them with the spin distribution in BBHs, finding that the two distributions are clearly in disagreement. Additionally, we discuss the implications of this work on our understanding of how the "relativistic reflection" spin measurement technique works, and discuss possible sources of systematic uncertainty that can bias our measurements.

Keywords: black holes; stellar mass black holes; astrophysical black holes; accretion; x-ray binary stars
Resolved Neutral Outflow from a Lensed Dusty Star-forming Galaxy at z = 2.09

We report the detection of a massive neutral gas outflow in the z = 2.09 gravitationally lensed dusty star-forming galaxy HATLAS J085358.9+015537 (G09v1.40), seen in absorption with the OH+(11-10) transition using spatially resolved (0"5 × 0"4) Atacama Large Millimeter/submillimeter Array (ALMA) observations. The blueshifted OH+ line is observed simultaneously with the CO(9-8) emission line and underlying dust continuum. These data are complemented by high-angular-resolution (0"17 × 0"13) ALMA observations of CH+(1-0) and underlying dust continuum, and Keck 2.2 μm imaging tracing the stellar emission. The neutral outflow, dust, dense molecular gas, and stars all show spatial offsets from each other. The total atomic gas mass of the observed outflow is 6.7 × 109M⊙, >25% as massive as the gas mass of the galaxy. We find that a conical outflow geometry best describes the OH+ kinematics and morphology and derive deprojected outflow properties as functions of possible inclination (0°38-64°). The neutral gas mass outflow rate is between 83 and 25,400 M⊙ yr-1, exceeding the star formation rate (788 ± 300 M⊙ yr-1) if the inclination is >3°6 (mass-loading factor = 0.3-4.7). Kinetic energy and momentum fluxes span (4.4-290) × 109 L⊙ and (0.1-3.7) × 1037 dyne, respectively (energy-loading factor = 0.013-16), indicating that the feedback mechanisms required to drive the outflow depend on the inclination assumed. We derive a gas depletion time between 29 and 1 Myr, but find that the neutral outflow is likely to remain bound to the galaxy unless the inclination is small and may be reaccreted if additional feedback processes do not occur.

Keywords: starburst galaxies; galaxy evolution; galaxy processes; high-redshift galaxies; interstellar absorption; strong gravitational lensing
Microgalaxies in LCDM

A fundamental prediction of the Lambda cold dark matter cosmology is the centrally divergent cuspy density profile of dark matter haloes. Density cusps render cold dark matter haloes resilient to tides, and protect dwarf galaxies embedded in them from full tidal disruption. The hierarchical assembly history of the Milky Way may therefore give rise to a population of "microgalaxies"; i.e., heavily stripped remnants of early accreted satellites, which can reach arbitrarily low luminosity. Assuming that the progenitor systems are dark matter dominated, we use an empirical formalism for tidal stripping to predict the evolution of the luminosity, size, and velocity dispersion of such remnants, tracing their tidal evolution across multiple orders of magnitude in mass and size. The evolutionary tracks depend sensitively on the progenitor distribution of stellar binding energies. We explore three cases that likely bracket most realistic models of dwarf galaxies: one where the energy distribution of the most tightly bound stars follows that of the dark matter, and two where stars are defined by either an exponential density or surface brightness profile. The tidal evolution in the size–velocity dispersion plane is quite similar for these three models, although their remnants may differ widely in luminosity. Microgalaxies are therefore best distinguished from globular clusters by the presence of dark matter; either directly, by measuring their velocity dispersion, or indirectly, by examining their tidal resilience. Our work highlights the need for further theoretical and observational constraints on the stellar energy distribution in dwarf galaxies.

Keywords: cold dark matter; dwarf spheroidal galaxies; low surface brightness galaxies; n-body simulations; star clusters; tidal disruption
Neutral Iron Emission Lines from the Dayside of KELT-9b: The GAPS Program with HARPS-N at TNG XX

We present the first detection of atomic emission lines from the atmosphere of an exoplanet. We detect neutral iron lines from the dayside of KELT-9b (Teq ∼ 4000 K). We combined thousands of spectrally resolved lines observed during one night with the HARPS-N spectrograph (R ∼ 115,000), mounted at the Telescopio Nazionale Galileo. We introduce a novel statistical approach to extract the planetary parameters from the binary mask cross-correlation analysis. We also adapt the concept of contribution function to the context of high spectral resolution observations, to identify the location in the planetary atmosphere where the detected emission originates. The average planetary line profile intersected by a stellar G2 binary mask was found in emission with a contrast of 84 ± 14 ppm relative to the planetary plus stellar continuum (40% ± 5% relative to the planetary continuum only). This result unambiguously indicates the presence of an atmospheric thermal inversion. Finally, assuming a modeled temperature profile previously published, we show that an iron abundance consistent with a few times the stellar value explains the data well. In this scenario, the iron emission originates at the 10-3-10-5 bar level.

Keywords: exoplanet atmospheres; exoplanet atmospheric composition; high resolution spectroscopy
The Planetary Ephemeris Program: Capability, Comparison, and Open Source Availability

We describe for the first time in scientific literature the Planetary Ephemeris Program (PEP), an open-source general-purpose astrometric data-analysis program. We discuss, in particular, the implementation of pulsar timing analysis, which was recently upgraded in PEP to handle more options. This implementation was done independently of other pulsar programs, with minor exceptions that we discuss. We illustrate the implementation of this capability by comparing the postfit residuals from the analyses of time-of-arrival observations by both PEP and TEMPO2. The comparison shows substantial agreement: 22 ns rms differences for 1065 pulse time-of-arrival measurements for the millisecond pulsar in a binary system, PSR J1909-3744 (pulse period 2.947108 ms; full width half maximum of pulse 43 μs), for epochs in the interval from 2002 December to 2011 February.

Keywords: publicly available software; astronomy software; open source software
Electromagnetic Cascade Emission from Neutrino-coincident Tidal Disruption Events

The potential association between Tidal Disruption Events and high-energy astrophysical neutrinos implies the acceleration of cosmic rays. These accelerated particles will initiate electromagnetic (EM) cascades spanning from keV to GeV energies via the processes related to neutrino production. We model the EM cascade and neutrino emissions by numerically solving the time-dependent transport equations, and discuss the implications for AT2019dsg and AT2019fdr in the X-ray and γ-ray bands. We show that the γ-ray constraints from Fermi can constrain the size of the radiation zone and the maximum energy of injected protons, and that the corresponding expected neutrino event numbers in follow-up searches are limited to be less than about 0.1. Depending on the efficiency of p γ interactions and the time at which the target photons peak, the X-ray and γ-ray signals can be expected closer to the peak of the optical-ultraviolet luminosity or to the time of the neutrino production.

Keywords: tidal disruption; radiative processes; neutrino astronomy
Techniques for Constraining the Abundance of Nonplanetary Substellar Objects

An interesting problem of relativistic astrophysics is the possible existence of non planetary Compact SubStellar Objects (CSSOs), such as black holes, but also non-standard objects such as boson stars. The challenge is to detect and distinguish them from ordinary planets. Here we present a new approach to this problem, which consists in detecting directly these CSSOs using exoplanet searches by transits, radial velocity measurements and astrometry and comparing the results to standard planet models.

Keywords: black holes
SDSS-IV/MaNGA: Can Impulsive Gaseous Inflows Explain Steep Oxygen Abundance Profiles and Anomalously Low-Metallicity Regions?

Gaseous inflows are necessary suppliers of galaxies' star-forming fuel, but are difficult to characterize at the survey scale. We use integral-field spectroscopic measurements of gas-phase metallicity and single-dish radio measurements of total atomic gas mass to estimate the magnitude and frequency of gaseous inflows incident on star-forming galaxies. We reveal a mutual correlation between steep oxygen abundance profiles between 0.25 and 1.5 Re, increased variability of metallicity between 1.25 and 1.75 Re, and elevated H I content at fixed total galaxy stellar mass. Employing a simple but intuitive inflow model, we find that galaxies with total stellar mass less than 1010.1 M⊙ have local oxygen abundance profiles consistent with reinvigoration by inflows. Approximately 10%-25% of low-mass galaxies possess signatures of recent accretion, with estimated typical enhancements of approximately 10%-90% in local gas mass surface density. Higher-mass galaxies have limited evidence for such inflows. The large diversity of H I mass implies that inflow-associated gas ought to reside far from the star-forming disk. We therefore propose that a combination of high H I mass, steep metallicity profile between 0.25 and 1.5 Re, and wide metallicity distribution function between 1.25 and 1.75 Re be employed to target possible hosts of inflowing gas for high-resolution radio follow-up.

Keywords: disk galaxies; galaxies; galactic and extragalactic astronomy; galaxy chemical evolution; galaxy evolution; chemical enrichment; neutral hydrogen clouds
Free-floating or Wide-orbit? Keck Adaptive-optics Observations of Free-floating Planet Candidates Detected with Gravitational Microlensing

Recent detections of extremely short-timescale microlensing events imply the existence of a large population of Earth- to Neptune-mass planets that appear to have no host stars. However, it is currently unknown whether these objects are truly free-floating planets or whether they are in wide orbits around a distant host star. Here, we present an analysis of high-resolution imaging observations of five free-floating planet candidates collected with the Keck telescope. If these candidates were actually wide-orbit planets, then the light of the host would appear at a separation of 40-60 mas from the microlensing source star. No such stars are detected. We carry out injection and recovery simulations to estimate the sensitivity to putative host stars at different separations. Depending on the object, the presented observations rule out 11%-36% of potential hosts assuming that the probability of hosting a planet does not depend on the host mass. The results are sensitive to the latter assumption, and the probability of detecting the host star in the analyzed images may be a factor of 1.9 ± 0.1 larger, if the exoplanet hosting probability scales as the first power of the host star mass, as suggested by recent studies of planetary microlensing events. We argue that deeper observations, for example with JWST, are needed to confidently confirm or refute the free-floating planet hypothesis.

Keywords: gravitational microlensing; free floating planets; high-resolution microlensing event imaging
Optical Counterpart to the Ultraluminous X-Ray Source in the UGC 6456 Galaxy

We report the identification of the optical counterpart to the transient ultraluminous X-ray source in the blue dwarf galaxy UGC 6456 (VII Zw 403). The source is highly variable in both the X-ray (by a factor of at least 100, 0.3-10 keV) and optical (by a factor of three, V-band) ranges. The peak X-ray luminosity of UGC 6456 ultraluminous X-ray source (ULX) exceeds 1040 erg s-1; the absolute magnitude when the source is optically bright is MV = -8.24 ± 0.11, which makes this source one of the brightest ULXs in the optical range. We found a correlation between the optical and X-ray fluxes (with a coefficient of 0.9 ± 0.3), which may indicate that the optical emission is produced by re-processing of the X-rays in outer parts of the optically thick wind coming from the supercritical accretion disk. Optical spectra of UGC 6456 ULX show broad and variable hydrogen and helium emission lines, which also confirms the presence of the strong wind.

Keywords: accretion; x-ray binary stars; x-ray point sources; x-ray identification
Modeling the Saturation of the Bell Instability Using Hybrid Simulations

The nonresonant streaming instability (Bell instability) plays a pivotal role in the acceleration and confinement of cosmic rays (CRs), yet the exact mechanism responsible for its saturation and the magnitude of the final amplified magnetic field have not been assessed from first principles. Using a survey of hybrid simulations (with kinetic ions and fluid electrons), we study the evolution of the Bell instability as a function of the parameters of the CR population. We find that at saturation, the magnetic pressure in the amplified field is comparable with the initial CR anisotropic pressure, rather than with the CR energy flux, as previously argued. These results provide a predictive prescription for the total magnetic field amplification expected in the many astrophysical environments where the Bell instability is important.

Keywords: cosmic rays; galactic cosmic rays; particle astrophysics; cosmic ray sources; high-energy cosmic radiation; high energy astrophysics; plasma astrophysics
Protostellar Chimney Flues: Are Jets and Outflows Lifting Submillimeter Dust Grains from Disks into Envelopes?

Low dust opacity spectral indices (β < 1) measured in the inner envelopes of class 0/I young stellar objects (age ~104-5 yr) have been interpreted as the presence of (sub-)millimeter dust grains in these environments. The density conditions and the lifetimes of collapsing envelopes have proven unfavorable for the growth of solids up to millimeter sizes. As an alternative, magnetohydrodynamical simulations suggest that protostellar jets and outflows might lift grains from circumstellar disks and diffuse them in the envelope. We reframe available data for the CALYPSO sample of Class 0/I sources and show tentative evidence for an anticorrelation between the value of β 1-3 mm measured in the inner envelope and the mass-loss rate of their jets and outflows, supporting a connection between the two. We discuss the implications that dust transport from the disk to the inner envelope might have for several aspects of planet formation. Finally, we urge for more accurate measurements of both correlated quantities and the extension of this work to larger samples, necessary to further test the transport scenario.

Keywords: interstellar medium; planet formation; circumstellar dust; stellar jets; stellar winds; millimeter astronomy
Bayesian Inference in Single-line Spectroscopic Binaries with a Visual Orbit

We present a Bayesian inference methodology for the estimation of orbital parameters on single-line spectroscopic binaries with astrometric data, based on the No-U-Turn sampler Markov chain Monte Carlo algorithm. Our approach is designed to provide a precise and efficient estimation of the joint posterior distribution of the orbital parameters in the presence of partial and heterogeneous observations. This scheme allows us to directly incorporate prior information about the system-in the form of a trigonometric parallax, and an estimation of the mass of the primary component from its spectral type-to constrain the range of solutions, and to estimate orbital parameters that cannot be usually determined (e.g., the individual component masses), due to the lack of observations or imprecise measurements. Our methodology is tested by analyzing the posterior distributions of well-studied double-line spectroscopic binaries treated as single-line binaries by omitting the radial velocity data of the secondary object. Our results show that the system's mass ratio can be estimated with an uncertainty smaller than 10% using our approach. As a proof of concept, the proposed methodology is applied to 12 single-line spectroscopic binaries with astrometric data that lacked a joint astrometric-spectroscopic solution, for which we provide full orbital elements. Our sample-based methodology allows us also to study the impact of different posterior distributions in the corresponding observations space. This novel analysis provides a better understanding of the effect of the different sources of information on the shape and uncertainty in the orbit and radial velocity curve.

Keywords: binary stars; astrometric binary stars; spectroscopic binary stars; bayesian statistics; markov chain monte carlo; trigonometric parallax; stellar parallax; visual binary stars; prior distribution; posterior distribution; mass ratio; stellar masses
WISEA J083011.95+283716.0: A Missing Link Planetary-mass Object

We present the discovery of WISEA J083011.95+283716.0, the first Y-dwarf candidate identified through the "Backyard Worlds: Planet 9" citizen science project. We identified this object as a red, fast-moving source with a faint W2 detection in multiepoch AllWISE and unWISE images. We have characterized this object with Spitzer and Hubble Space Telescope's (HST) follow-up imaging. With mid-infrared detections in Spitzer's ch1 and ch2 bands and flux upper limits in HST F105W and F125W filters, we find that this object is both very faint and has extremely red colors (ch1 - ch2 = 3.25 ± 0.23 mag, F125W - ch2 ≥ 9.36 mag), consistent with a Teff ∼ 300 K source, as estimated from the known Y-dwarf population. A preliminary parallax provides a distance of ${11.1}_{-1.5}^{+2.0}$ pc, leading to a slightly warmer temperature of ∼350 K. The extreme faintness and red HST and Spitzer colors of this object suggest that it may be a link between the broader Y-dwarf population and the coldest known brown dwarf WISE J0855-0714, and may highlight our limited knowledge of the true spread of Y-dwarf colors. We also present four additional "Backyard Worlds: Planet 9" late-T brown dwarf discoveries within 30 pc.

Keywords: brown dwarfs; y dwarfs; hst photometry; hubble space telescope; near infrared astronomy; infrared telescopes; infrared astronomy; infrared photometry; infrared sources; space telescopes; proper motions; parallax