adsabs/SciX_UAT_keywords huggingface dataset:
Observation of Gamma Rays up to 320 TeV from the Middle-aged TeV Pulsar Wind Nebula HESS J1849-000

Gamma rays from HESS J1849-000, a middle-aged TeV pulsar wind nebula (PWN), are observed by the Tibet air shower array and the muon detector array. The detection significance of gamma rays reaches 4.0σ and 4.4σ levels above 25 TeV and 100 TeV, respectively, in units of the Gaussian standard deviation σ. The energy spectrum measured between 40 TeV < E < 320 TeV for the first time is described with a simple power-law function of ${dN}/{dE}={(2.86\pm 1.44)\times {10}^{-16}(E/40\,\mathrm{TeV})}^{-2.24\pm 0.41}\,{\mathrm{TeV}}^{-1}\,{\mathrm{cm}}^{-2}\,{{\rm{s}}}^{-1}$ . The gamma-ray energy spectrum from the sub-TeV (E < 1 TeV) to sub-PeV (100 TeV < E < 1 PeV) ranges, including the results of previous studies, can be modeled with the leptonic scenario, i.e., inverse Compton scattering by high-energy electrons accelerated by the PWN of PSR J1849-0001. On the other hand, the gamma-ray energy spectrum can also be modeled with the hadronic scenario in which gamma rays are generated from the decay of neutral pions produced by collisions between accelerated cosmic-ray protons and the ambient molecular cloud found in the gamma-ray-emitting region. The cutoff energy of cosmic-ray protons E p,cut is estimated as ${\mathrm{log}}_{10}({E}_{{\rm{p}},\mathrm{cut}}/\mathrm{TeV})={3.73}_{-0.66}^{+2.98}$ , suggesting that protons are accelerated up to the PeV energy range. Our study thus proposes that HESS J1849-000 should be further investigated as a new candidate as a Galactic PeV cosmic-ray accelerator, or "PeVatron."

Keywords: galactic cosmic rays; pulsar wind nebulae; gamma-ray sources; gamma-ray astronomy; gamma-ray observatories
Kinematical Fluctuations Vary with Galaxy Surface Mass Density

The Galaxy inner parts are generally considered to be optically symmetric, as well as kinematically symmetric for most massive early-type galaxies. At the lower-mass end, many galaxies contain lots of small patches in their velocity maps, causing their kinematics to be nonsmooth in small scales and far from symmetry. These small patches can easily be mistaken for measurement uncertainties and have not been well discussed. We used the comparison of observations and numerical simulations to demonstrate the small patches existence beyond uncertainties. For the first time we have found that the fluctuation degrees have an approximate inverse loglinear relation with the galaxy stellar surface mass densities. This tight relation among galaxies that do not show obvious optical asymmetry that traces environmental perturbations indicates that stellar motion in galaxies has inherent asymmetry besides external environment influences. The degree of the kinetic asymmetry is closely related to and constrained by the intrinsic properties of the host galaxy.

Keywords: galaxy kinematics; galaxy dynamics; galaxy structure; dark matter
The Surface of (16) Psyche from Thermal Emission and Polarization Mapping

The asteroid (16) Psyche is the largest of the M-type asteroids, which have been hypothesized to be the cores of disrupted planetesimals and the parent bodies of the iron meteorites. While recent evidence has collected against a pure metal composition for Psyche, its spectrum and radar properties remain anomalous. We observed (16) Psyche in thermal emission with the Atacama Large Millimeter/submillimeter Array at a resolution of 30 km over two-thirds of its rotation. The diurnal temperature variations are at the ~10 K level over most of the surface and are best fit by a smooth surface with a thermal inertia of 280 ± 100 J m-2 K-1 s-1/2. We measure a millimeter emissivity of 0.61 ± 0.02, which we interpret via a model that treats the surface as a porous mixture of silicates and metals, where the latter may take the form of iron sulfides/oxides or, alternatively, conducting metallic inclusions. The emissivity indicates a metal content of no less than 20% and potentially much higher, but the polarized emission that should be present for a surface with ≥20% metal content is almost completely absent. This requires a highly scattering surface, which may be due to the presence of reflective metallic inclusions. If such is the case, a consequence is that metal-rich asteroids may produce less polarized emission than metal-poor asteroids, exactly the opposite prediction from standard theory, arising from the dominance of scattering over the bulk material properties.

Keywords: solar system; solar system astronomy; asteroids; asteroid surfaces; small solar system bodies; radio interferometry
No Significant Redshift Evolution in the Intrinsic Scatter of the M •–M ⋆ Relation for Overmassive Black Holes

In the local Universe, the ratio between the mass of a central black hole and the stellar mass of its host galaxy is ∼0.1%. Recently, JWST discovered numerous galaxies at z > 4 that seem to deviate from the local relation, with black holes overmassive by 10–100 times. Similar galaxies were also discovered at cosmic noon. The intrinsic scatter in the relation describes how much the evolutionary histories of the single galaxies deviate from the mean evolutionary pattern of their parent data set. This Research Note examines whether a cosmic evolution of the intrinsic scatter can be detected by assessing its value for data sets in various redshift ranges. Using data from the local Universe (z < 0.055), low (0.4 ≤ z ≤ 0.9), intermediate (0.9 ≤ z ≤ 4), and high (z > 4) redshift, we conclude that there is no statistically significant redshift evolution of the intrinsic scatter.

Keywords: supermassive black holes; galaxy evolution; high-redshift galaxies; surveys
Recovering Thermodynamics from Spectral Profiles Observed by IRIS. (II). Improved Calculation of the Uncertainties Based on Monte Carlo Experiments

Observations by the Interface Region Imaging Spectrograph (IRIS) of the Mg II h & k spectral lines have provided a new diagnostic window toward knowledge of the complex physical conditions in the solar chromosphere. Theoretical efforts focused on understanding the behavior of these lines have allowed us to obtain a better and more accurate vision of the chromosphere. These efforts include forward modeling, numerical simulations, and inversions. In this paper, we focus our attention on the uncertainties associated with the thermodynamic model atmosphere obtained after the inversion of the Mg II h & k lines. We have used ≈50,000 synthetic representative profiles of the IRIS2 database to characterize the most important sources of uncertainties in the inversion process, viz.: the inherent noise of the observations, the random initialization process, and the selection criteria in a high-dimensional space. We have applied a Monte Carlo approach to this problem. Thus, for a given synthetic representative profile, we have created five randomized noise realizations (representative of the most popular exposure times in the IRIS observations), and inverted these profiles five times with different inversion initializations. The resulting 25 inverted profiles, fit to noisy data, and model atmospheres are then used to determine the uncertainty in the model atmosphere, based on the standard deviation and empirical selection criteria for the goodness of fit. With this approach, the new uncertainties of the models available in the IRIS2 database are more reliable at the optical depths where the Mg II h & k lines are sensitive to changes in the thermodynamics.

Keywords: solar chromosphere; radiative transfer
A Markedly Expanded Sample of Candidate X-Ray-emitting Isolated Neutron Stars

The current sample of 12 radio-quiet isolated neutron stars that emit strongly in X-rays (XINSs) is both small and heterogeneous, limiting its usefulness for understanding the physics of neutron star atmospheres and cooling rates and for constraining the equation of state of neutron degenerate matter. Utilizing the ROSAT 1RXS and 2RXS data sets, in conjunction with the Sloan Digital Sky Survey Data Release 17 and other companion multiwavelength surveys, we have extended previous searches for blank-field X-ray source candidate XINSs, ultimately recovering two known XINSs while identifying 46 new, unstudied candidate fields devoid of likely multiwavelength counterparts. In this publication, we describe our selection approach and provide detailed information regarding our sample of new candidate XINSs. Future opportunities to verify or to refute these X-ray sources as isolated neutron stars by obtaining more accurate X-ray source positions, quality X-ray spectra, or deeper optical imaging are also discussed.

Keywords: neutron stars; x-ray surveys
Interactions between Filament Fibrils and a Network Field

Filaments are common structures in the solar atmosphere, and usually interact with their surrounding magnetic fields. However, interactions between filaments and network fields are rare. Here, we report interactions between filament fibrils and a nearby network field in the quiet Sun by employing observations from the New Vacuum Solar Telescope (NVST) and Solar Dynamics Observatory. NVST Hα images show that several filament fibrils separated from the main body of the filament, and moved sideward. While a fibril met the network field, the movement of the fibril segment corresponding to the network field slowed down. Subsequently, weak extremely ultraviolet brightenings appeared near the interface of the filament and the network field, and then the fibril materials began to converge toward the network field. Meanwhile, continuous redshift signal enhancements appeared in the corresponding Dopplergrams, accompanying the convergences of the fibril materials. About 10 and 35 minutes later, two other similar processes occurred again. These observations imply that the network field blocks movements of the filament fibrils and weak magnetic reconnections between the blocked fibrils and the network field take place. We suggest that new field lines developed due to the magnetic reconnections, along which fibril materials fell down into the lower solar atmosphere. These results provide a new picture of filament material drainage.

Keywords: solar magnetic reconnection; solar filaments
Chandra X-Ray Observations of V830 Tau: A T Tauri Star Hosting an Evanescent Planet

The radial velocity study by Donati et al. (2016) reported the detection of a close-in giant planet in a 4.93 day orbit around the ~2 Myr old weak-lined T Tauri star V830 Tau. Because of the stringent timescale constraints that a very young host star like V830 Tau would place on hot-Jupiter formation models and inward-migration mechanisms, independent confirmation of the planet's existence is needed but so far has not been obtained. We present new Chandra X-ray observations of V830 Tau. The Chandra observations in combination with previous XMM-Newton observations reveal strong, variable X-ray emission with an X-ray luminosity spanning the range log Lx = 30.10-30.87 erg s-1. Chandra High Energy Transmission Grating spectra show emission lines formed over a range of plasma temperatures from ~4 MK (Ne IX) to ~16 MK (S XV). At the separation of the reported planet (0.057 au) the X-ray flux is ~106-107 times greater than the Sun's X-ray flux at Jupiter. We provide estimates of the X-ray ionization and atmospheric heating rates at the planet's separation and identify areas of uncertainty that will need to be addressed in any future atmospheric models.

Keywords: t tauri stars; x-ray stars
FERIA: Flat Envelope Model with Rotation and Infall under Angular Momentum Conservation

Radio observations of low-mass star formation in molecular spectral lines have rapidly progressed since the advent of the Atacama Large Millimeter/submillimeter Array (ALMA). The gas distribution and its kinematics within a few hundreds of astronomical unit scale around a Class 0-I protostar are spatially resolved, and the region where a protostellar disk is being formed is now revealed in detail. In such studies, it is essential to characterize the complex physical structure around a protostar consisting of an infalling envelope, a rotationally supported disk, and an outflow. For this purpose, we have developed a general-purpose computer code "FERIA" (Flat Envelope model with Rotation and Infall under Angular momentum conservation) to generate the image data cube based on the infalling-rotating envelope model and the Keplerian disk model, both of which are often used in observational studies. In this paper, we present the description and the user manual of FERIA and summarize caveats in actual applications. This program outputs cube FITS files, which can be used for direct comparison with observations. It can also be used to generate mock data for machine/deep learning. Examples of these applications are described and discussed to demonstrate how the model analyses work with actual observational data.

Keywords: protostars; protoplanetary disks; interstellar line emission; young stellar objects; bok globules
What GW170729's Exceptional Mass and Spin Tells Us about Its Family Tree

Gravitational-wave observations give a unique insight into the formation and evolution of binary black holes. We use gravitational-wave measurements to address the question of whether GW170729's source, which is (probably) the most massive binary and the system with the highest effective inspiral spin, could contain a black hole which is a previous merger remnant. Using the inferred mass and spin of the system, and the empirically determined population of binary black holes, we compute the evidence for the binary being second-generation compared with first-generation. We find moderate evidence (a Bayes factor of ~6-7) that the mass and spin better match a second-generation merger, but folding in the expectation that only a small fraction of mergers are second-generation, we conclude that there is no strong evidence that GW170729 was the result of a second-generation merger. The results are sensitive to the assumed mass distribution, and future detections will provide more robust reconstructions of the binary black hole population.

Keywords: gravitational wave sources; gravitational wave astronomy; astrophysical black holes
CLASSY. VI. The Density, Structure, and Size of Absorption-line Outflows in Starburst Galaxies

Galaxy formation and evolution are regulated by the feedback from galactic winds. Absorption lines provide the most widely available probe of winds. However, since most data only provide information integrated along the line of sight, they do not directly constrain the radial structure of the outflows. In this paper, we present a method to directly measure the gas electron density in outflows (n e ), which in turn yields estimates of outflow cloud properties (e.g., density, volume filling factor, and sizes/masses). We also estimate the distance (r n ) from the starburst at which the observed densities are found. We focus on 22 local star-forming galaxies primarily from the COS Legacy Archive Spectroscopic SurveY (CLASSY). In half of them, we detect absorption lines from fine-structure excited transitions of Si II (i.e., Si II*). We determine n e from relative column densities of Si II and Si II*, given Si II* originates from collisional excitation by free electrons. We find that the derived n e correlates well with the galaxy's star formation rate per unit area. From photoionization models or assuming the outflow is in pressure equilibrium with the wind fluid, we get r n ~ 1-2r * or ~5r *, respectively, where r * is the starburst radius. Based on comparisons to theoretical models of multiphase outflows, nearly all of the outflows have cloud sizes large enough for the clouds to survive their interaction with the hot wind fluid. Most of these measurements are the first ever for galactic winds detected in absorption lines and, thus, will provide important constraints for future models of galactic winds.

Keywords: galaxy evolution; galaxy winds; galaxy kinematics; starburst galaxies; ultraviolet astronomy; galaxy spectroscopy
The Green Bank 820 MHz Pulsar Survey. I. Survey Overview and Initial Results

The Green Bank 820 MHz pulsar survey covers ≃173 deg2 in the Cygnus X region of the Galaxy, centered on l = 84.°5 and b = 1.°5. Significant star formation is present in this region, and lines of sight pass through three arms of the Galaxy (Orion–Cygnus, Perseus, and an outer arm). Using the Green Bank Telescope, we recorded 200 MHz of bandwidth for 4.5 minutes at 81.92 μs resolution for each of 3457 observed survey pointings during 2016 and 2017, covering about two-thirds of the total area. We searched these data for pulsars and report the discovery of six new pulsars—PSRs J2016+3820, J2016+4231, J2019+3810, J2035+3538, J2035+3655, and J2041+4551—and the codiscovery of PSR J2057+4701. PSR J2035+3655 is in a short (4.5 hr) binary orbit; we report the full binary solution and weakly constrain the mass of the pulsar via a marginal (2σ) detection of the Shapiro delay. We also searched the survey data for known pulsars to estimate the survey's sensitivity and measured 820 MHz pulse widths and flux density for 20 detected sources. For sources that were also detected in the Green Bank North Celestial Cap survey at 350 MHz, we measure scattering parameters and compare to expectations for the region. With these results, we revisit the population estimates that motivated this survey and consider the impact of the survey's yield on their underlying models. We note an apparent underestimate in dispersion measure predictions from typical Galactic electron density models in the survey region, and discuss future observation strategies.

Keywords: radio pulsars; radio astronomy; surveys
Evolution of C IV Absorbers. I. The Cosmic Incidence

We present a large high-resolution study of the distribution and evolution of C IV absorbers, including the weakest population with equivalent widths ${W}_{r}\lt 0.3\,\mathring{\rm A} $ . By searching 369 high-resolution, high signal-to-noise ratio spectra of quasars at $1.1\leqslant {z}_{\mathrm{em}}\leqslant 5.3$ from Keck/HIRES and VLT/UVES, we find 1268 C IV absorbers with ${W}_{r}\geqslant 0.05$ Å (our ∼50% completeness limit) at redshifts $1.0\leqslant z\leqslant 4.75$ . A Schechter function describes the observed equivalent width distribution with a transition from power-law to exponential decline at ${W}_{r}\gtrsim 0.5\,\mathring{\rm A} $ . The power-law slope α rises by ∼7%, and the transition equivalent width W⋆ falls by ∼20% from $\langle z\rangle =1.7$ to 3.6. We find that the comoving redshift path density, ${dN}/{dX}$ , of ${W}_{r}\geqslant 0.05$ Å absorbers rises by ∼1.8 times from z ≃ 4.0 to 1.3, while the ${W}_{r}\geqslant 0.6$ Å ${dN}/{dX}$ rises by a factor of ∼8.5. We quantify the observed evolution by a model in which ${dN}/{dX}$ decreases linearly with increasing redshift. The model suggests that populations with larger ${W}_{r}$ thresholds evolve faster with redshift and appear later in the universe. The cosmological TECHNICOLOR DAWN simulations at z = 3-5 overproduce the observed abundance of absorbers with ${W}_{r}\leqslant 0.3\,\mathring{\rm A} $ while yielding better agreement at higher ${W}_{r}$ . Our empirical linear model successfully describes C IV evolution in the simulations and the observed evolution of ${W}_{r}\geqslant 0.6$ Å C IV for the past $\sim 12\,\mathrm{Gyr}$ . Combining our measurements with the literature gives us a picture of C IV absorbing structures becoming more numerous and/or larger in physical size over the last $\approx 13\,\mathrm{Gyr}$ of cosmic time (z ∼ 6-0).

Keywords: quasar absorption line spectroscopy; circumgalactic medium; intergalactic medium; galaxy evolution; high resolution spectroscopy
Probing the Length of the Heliospheric Tail with Energetic Neutral Atoms (ENAs) from 0.52 to 80 keV

The shape of the heliosphere is currently under active debate. Energetic neutral atoms (ENAs) offer the best method for investigating the global structure of the heliosphere. To date, the Interstellar Boundary Explorer (IBEX) and the Ion and Neutral Camera (INCA) that was on board Cassini provide the only global ENA observations of the heliosphere. While extensive modeling has been done at IBEX-Hi energies (0.52-6 keV), no global ENA modeling has been conducted for INCA energies (5.2-55 keV). Here, we use an ENA model of the heliosphere based on hybrid results that capture the heating and acceleration of pickup ions (PUIs) at the termination shock to compare modeled global ENA results with IBEX-Hi and INCA observations using both a long- and short-tail model of the heliosphere. We find that the modeled ENA results for the two heliotail configurations produce similar results from the IBEX-Hi through the INCA energies. We conclude from our modeled ENAs, which only include PUI acceleration at the termination shock, that ENA observations in currently available energy ranges are insufficient for probing the shape and length of the heliotail. However, as a prediction for the future IMAP-Ultra mission (3-300 keV) we present modeled ENA maps at 80 keV, where the cooling length (~600 au) is greater than the distance where the long- and short-heliotail models differ (~400 au), and find that IMAP-Ultra should be able to identify the shape of the heliotail, predicting differences in the north lobe to downwind flux ratio between the models at 48%.

Keywords: heliosphere; solar system; heliosheath; heliopause; termination shock; interstellar medium; the sun; magnetohydrodynamics; magnetohydrodynamical simulations
Deconfusing the Confusogram: Getting New Insights from Zeeman Doppler Imaging

Zeeman Doppler Imaging (ZDI) is a powerful tool for characterizing the strength and topology of stellar magnetic fields. In this research note, we present a new way to visualize the typical results from ZDI for an ensemble of stars, addressing some of the concerns with the standard "confusogram" approach to illustrating the data. Our publicly available plotting methods further enable an accessible means to consider variability in the inferred magnetic field topologies from repeated observations, as we demonstrate with the literature ZDI data on M dwarfs.

Keywords: stellar magnetic fields; m dwarf stars
The K2 and TESS Synergy. II. Revisiting 26 Systems in the TESS Primary Mission

The legacy of NASA's K2 mission has provided hundreds of transiting exoplanets that can be revisited by new and future facilities for further characterization, with a particular focus on studying the atmospheres of these systems. However, the majority of K2-discovered exoplanets have typical uncertainties on future times of transit within the next decade of greater than 4 hr, making observations less practical for many upcoming facilities. Fortunately, NASA's Transiting Exoplanet Survey Satellite (TESS) mission is reobserving most of the sky, providing the opportunity to update the ephemerides for ~300 K2 systems. In the second paper of this series, we reanalyze 26 single-planet, K2-discovered systems that were observed in the TESS primary mission by globally fitting their K2 and TESS light curves (including extended mission data where available), along with any archival radial velocity measurements. As a result of the faintness of the K2 sample, 13 systems studied here do not have transits detectable by TESS. In those cases, we refit the K2 light curve and provide updated system parameters. For the 23 systems with M * ≳ 0.6 M ⊙, we determine the host star parameters using a combination of Gaia parallaxes, spectral energy distribution fits, and MESA Isochrones and Stellar Tracks stellar evolution models. Given the expectation of future TESS extended missions, efforts like the K2 and TESS Synergy project will ensure the accessibility of transiting planets for future characterization while leading to a self-consistent catalog of stellar and planetary parameters for future population efforts.

Keywords: exoplanet catalogs; exoplanet astronomy; exoplanet systems; exoplanets; ephemerides