Sazuna/UAT_keywords huggingface dataset:
Shocked Narrow-angle Tail Radio Galaxies: Simulations and Emissions. We present a numerical study of the interactions between the elongated active galactic nuclei outflows representing an evolved, narrow-angle tail (NAT) radio galaxy and planar, transverse ICM shock fronts characteristic of those induced by galaxy cluster mergers (incident Mach numbers 2-4). The simulated NAT formation was reported previously in O’Neill et al. Our simulations utilize a three-dimensional, Eulerian magnetohydrodynamic code along with energy-dependent Eulerian transport of passive cosmic ray electrons. Our analysis of the shock/NAT interaction applies a Riemann problem-based theoretical model to interpret complex shock front behavior during passage through the highly heterogeneous structures of the simulated NAT tails. In addition to shock compression, shock-induced vortical motions are observed within the tails that contribute to coherent turbulent dynamo processes that continue to amplify the magnetic fields in the tails well after initial shock compression. We analyze synthetic radio observations spanning the NAT-shock interaction period, and examine the brightness, spectral and polarization properties of our shock-rejuvenated radio tails, as well as the extent to which the pre-shock states of the plasma and particle populations in our tails influence post-shock observations. Finally, we evaluate our findings in the possible context of a physical analogy to our simulated NAT providing the precursor to a cluster “radio relic” associated with an impacting ICM shock.

Keywords: Galaxy clusters, Tailed radio galaxies, Shocks, Intracluster medium, Magnetohydrodynamical simulations
Untangling the Origin of Molecular Hydrogen in the Lunar Exosphere. In situ experiments from the Apollo missions confirmed the presence of a tenuous exosphere on the Moon comprised of atoms and light molecular species. Of the most prominent volatiles found in the exosphere, molecular hydrogen (H2) has drawn considerable attention because the confirmed detection of surface water has led many scientists to believe that proton bombardment of silicate minerals from the solar wind is the mechanism by which this water forms. As molecular hydrogen formation is a competing mechanism to bound OH/H2O in the regolith, experimental studies are needed to determine the efficiency of molecular hydrogen formation from the solar wind. Here we show that, under simulated lunar conditions, the formation, storage, and release of molecular deuterium—as a proxy of molecular hydrogen—from deuteron implanted olivine is facile. Secondary ion mass spectrometry results reveal that diffusion processes also enrich grains with deuterium at depths beyond the maximum penetration depth of the incident ions close to 100 nm. In addition, the maximum yield of molecular deuterium escaping the amorphous rims under simulated lunar conditions strongly supports previous studies, which claim that the solar wind represents the dominant source of exospheric molecular hydrogen.

Keywords: Solar wind, Space weather, Laboratory astrophysics, Lunar atmosphere
Constraining the Stochastic Gravitational Wave from String Cosmology with Current and Future High-frequency Detectors. Pre-Big Bang models in string cosmology predict a relic background of gravitational wave radiation in the early universe. The spectrum of this background shows that the energy density rises rapidly with frequency, which is an interesting target for high-frequency (i.e., kilohertz) detectors. In this paper, we discussed the constraining power of multiple configurations of current and future gravitational wave detector (GWD) networks to the stochastic background predicted in string cosmology. The constraining power is jointly determined by the overlap reduction function and the sensitivity curves of multiple detectors. And we further elaborated on the possible contribution of a future Chinese detector and a kilohertz detector to the constraining power of detector network for stochastic background in string cosmology. Our results show that the detectability of the GWD network for the string cosmology gravitational wave background will improve considerably with the joining of a Chinese detector. This is because a Chinese detector (e.g., located at Wuhan), together with KAGRA, has a better overlap reduction function than the laser interferometer gravitational wave observatory detector pair, and therefore lead to more stringent limits for stochastic background detection. And with ideal overlap reduction function, namely, colocated detectors, a kilohertz sensitivity curve has better performance than previous detectors for stochastic background detection. Finally, the results are compared with the limitations given by the observational constraint of the Big Bang nucleosynthesis bound.

Keywords: Observational cosmology, Gravitational wave detectors, Gravitational wave sources
The Effect of Land Fraction and Host Star Spectral Energy Distribution on the Planetary Albedo of Terrestrial Worlds. The energy balance and climate of planets can be affected by the reflective properties of their land, ocean, and frozen surfaces. Here we investigate the effect of host star spectral energy distribution (SED) on the albedo of these surfaces using a one-dimensional energy balance model. Incorporating spectra of M-, K-, G-, and F-dwarf stars, we determined the effect of varying fractional and latitudinal distribution of land and ocean surfaces as a function of host star SED on the overall planetary albedo, climate, and ice-albedo feedback response. While noting that the spatial distribution of land masses on a given planet will have an effect on the overall planetary energy balance, we find that terrestrial planets with higher average land/ocean fractions are relatively cooler and have higher albedo regardless of star type. For Earth-like planets orbiting M-dwarf stars, the increased absorption of water ice in the near-infrared, where M-dwarf stars emit much of their energy, resulted in warmer global mean surface temperatures, ice lines at higher latitudes, and increased climate stability as the ice-albedo feedback became negative at high land fractions. Conversely, planets covered largely by ocean, and especially those orbiting bright stars, had a considerably different energy balance due to the contrast between the reflective land and the absorptive ocean surface, which in turn resulted in warmer average surface temperatures than land-covered planets and a stronger potential ice-albedo feedback. While dependent on the properties of individual planetary systems, our results place some constraints on a range of climate states of terrestrial exoplanets based on albedo and incident flux.

Keywords: Ice formation, Exoplanets, Exoplanet surface composition, Exoplanet astronomy, Exoplanet surface variability, Exoplanet surface characteristics, Planetary science, Planet hosting stars, Habitable planets
Quasi-simultaneous INTEGRAL, SWIFT, and NuSTAR Observations of the New X-Ray Clocked Burster 1RXS J180408.9-342058. We report the quasi-simultaneous INTEGRAL, SWIFT, and NuSTAR observations showing spectral state transitions in the neutron star low-mass X-ray binary 1RXS J180408.9-342058 during its 2015 outburst. We present results of the analysis of high-quality broad energy band (0.8-200 keV) data in three different spectral states: high/soft, low/very-hard, and transitional state. The broadband spectra can be described in general as the sum of thermal Comptonization and reflection due to illumination of an optically thick accretion disk. During the high/soft state, blackbody emission is generated from the accretion disk and the surface of the neutron star. This emission, measured at a temperature of kT bb ∼ 1.2 keV, is then Comptonized by a thick corona with an electron temperature of ∼2.5 keV. For the transitional and low/very-hard state, the spectra are successfully explained with emission from a double Comptonizing corona. The first component is described by thermal Comptonization of seed disk/neutron star photons (kT bb ∼ 1.2 keV) by a cold corona cloud with kT  e  ∼ 8-10 keV, while the second one originates from lower temperature blackbody photons (kT bb ≤ 0.1 keV) Comptonized by a hot corona (kT  e  ∼ 35 keV). Finally, from NuSTAR observations, there is evidence that the source is a new clocked burster. The average time between two successive X-ray bursts corresponds to ∼7.9 and ∼4.0 ks when the persistent emission decreases by a factor of ∼2, moving from a very hard to transitional state. The accretion rate (∼ 4× {10}-9 {M}☉  {yr}}-1) and the decay time of the X-ray bursts longer than ∼30 s suggest that the thermonuclear emission is due to mixed H/He burning triggered by thermally unstable He ignition.

Keywords: X-ray astronomy, Binary stars, Gamma-ray bursters, Low-mass x-ray binary stars, Gamma-ray astronomy
NuSTAR Observations of the Unidentified INTEGRAL Sources: Constraints on the Galactic Population of HMXBs. The NuSTAR Legacy program titled Unidentified INTEGRAL Sources targeted faint hard X-ray sources revealed by INTEGRAL in the Galactic plane in order to provide conclusive identification of their nature and insights on the population of faint hard X-ray sources. The NuSTAR and Swift X-Ray Telescope observations obtained in 2015-2017 contributed to the successful identification of five persistent sources. Here, we report on the spectral and variability analyses that helped to consolidate the classifications of IGR J10447-6027, IGR J16181-5407, and IGR J20569+4940 as active galactic nuclei and IGR J17402-3656 as an intermediate polar. An optical spectrum of the blazar IGR J20569+4940 is also presented. Combining these results with successful identifications of other such faint and persistent INTEGRAL sources reported in the literature, we investigate possible implications for the population of persistent high-mass X-ray binaries (HMXBs) below the identification completion limit of the INTEGRAL survey. The current trend hints at a deficit of persistent HMXBs below F 17-60 keV = 10-11 erg cm-2 s-1, but additional efforts dedicated to classifying faint hard X-ray sources are needed before we can draw solid conclusions.

Keywords: BL Lacertae objects, Blazars, High mass x-ray binary stars, X-ray active galactic nuclei, X-ray sources, Cataclysmic variable stars
Gravitational Waves from the Inspiral of Supermassive Black Holes in Galactic-scale Simulations. We study the orbital evolution and gravitational wave (GW) emission of supermassive black hole (SMBH) binaries formed in gas-free mergers of massive early-type galaxies using the hybrid tree-regularized N-body code KETJU. The evolution of the SMBHs and the surrounding galaxies is followed self-consistently from the large-scale merger down to the final few orbits before the black holes coalesce. Post-Newtonian corrections are included up to PN3.5 level for the binary dynamics, and the GW calculations include the corresponding corrections up to PN1.0-level. We analyze the significance of the stellar environment on the evolution of the binary and the emitted GW signal during the final GW emission dominated phase of the binary hardening and inspiral. Our simulations are compared to semi-analytic models that have often been used for making predictions for the stochastic GW background emitted by SMBHs. We find that the commonly used semi-analytic parameter values produce large differences in merger timescales and eccentricity evolution, but result in only ∼ 10 % differences in the GW spectrum emitted by a single binary at frequencies f≳ {10}-1 {yr}}-1, which are accessible by current pulsar timing arrays. These differences are in part caused by the strong effects of the SMBH binaries on the surrounding stellar population, which are not included in the semi-analytic models.

Keywords: Supermassive black holes, Galaxy mergers, N-body simulations, Gravitational wave sources
Model-independent Determination of Cosmic Curvature Based on the Padé Approximation. Given observations of the standard candles and cosmic chronometers, we apply Padé parameterization to the comoving distance and the Hubble parameter to find out how stringently the constraint is set to the curvature parameter by the data. A weak informative prior is introduced in the modeling process to keep the inference away from the singularities. Bayesian evidence for a different order of Padé parameterizations is evaluated during the inference to select the most suitable parameterization in light of the data. The data we used prefer a parameterization form of comoving distance as {D}01(z)=\tfrac{{a}0z}{1+{b}1z} as well as a competitive form {D}02(z)=\tfrac{{a}0z}{1+{b}1z+{b}2{z}2}. Similar constraints on the spatial curvature parameter are established by those models and given the Hubble constant as a byproduct: {{{Ω }}}k={0.25}-0.13+0.14 (68% confidence level; CL), H 0 = 67.7 ± 2.0 km s-1 Mpc-1 (68% CL) for D 01, and Ω k  = - 0.01 ± 0.13 (68% CL), H 0 = 68.8 ± 2.0 km s-1 Mpc-1 (68% CL) for D 02. The evidence from different models demonstrates the qualitative analysis of Padé parameterizations for the comoving distance.

Keywords: Cosmology, Cosmological parameters
The ALMA Spectroscopic Survey in the HUDF: Constraining Cumulative CO Emission at 1 ≲ z ≲ 4 with Power Spectrum Analysis of ASPECS LP Data from 84 to 115 GHz. We present a power spectrum analysis of the ALMA Spectroscopic Survey Large Program (ASPECS LP) data from 84 to 115 GHz. These data predominantly probe small-scale fluctuations (k = 10-100 h Mpc-1) in the aggregate CO emission in galaxies at 1≲ z ≲ 4. We place an integral constraint on CO luminosity functions (LFs) in this redshift range via a direct measurement of their second moments in the three-dimensional (3D) autopower spectrum, finding a total CO shot-noise power {P}CO,{CO}}({k}CO(2-1)})≤slant 1.9× {10}2 μK2 (Mpc h -1)3. This upper limit (3σ) is consistent with the observed ASPECS CO LFs in Decarli et al. but rules out a large space in the range of {P}CO,{CO}}({k}CO(2-1)}) inferred from these LFs, which we attribute primarily to large uncertainties in the normalization Φ* and knee L * of the Schechter-form CO LFs at z &gt; 2. Also, through power spectrum analyses of ASPECS LP data with 415 positions from galaxies with available optical spectroscopic redshifts, we find that contributions to the observed mean CO intensity and shot-noise power of MUSE galaxies are largely accounted for by ASPECS blind detections. Finally, we sum the fluxes from individual blind CO detections to yield a lower limit on the mean CO surface brightness at 99 GHz of &lt; {T}CO}&gt; =0.55+/- 0.02 μK, which we estimate represents 68%-80% of the total CO surface brightness at this frequency.

Keywords: Molecular gas, High-redshift galaxies
The Sloan Digital Sky Survey Reverberation Mapping Project: Initial C IV Lag Results from Four Years of Data. We present reverberation-mapping (RM) lags and black hole mass measurements using the C IV λ1549 broad emission line from a sample of 348 quasars monitored as a part of the Sloan Digital Sky Survey RM Project. Our data span four years of spectroscopic and photometric monitoring for a total baseline of 1300 days, allowing us to measure lags up to ∼750 days in the observed frame (this corresponds to a rest-frame lag of ∼300 days in a quasar at z = 1.5 and ∼190 days at z = 3). We report significant time delays between the continuum and the C IV λ1549 emission line in 48 quasars, with an estimated false-positive detection rate of 10%. Our analysis of marginal lag measurements indicates that there are on the order of ∼100 additional lags that should be recoverable by adding more years of data from the program. We use our measurements to calculate black hole masses and fit an updated C IV radius-luminosity relationship. Our results significantly increase the sample of quasars with C IV RM results, with the quasars spanning two orders of magnitude in luminosity toward the high-luminosity end of the C IV radius-luminosity relation. In addition, these quasars are located at some of the highest redshifts (z ≈ 1.4-2.8) of quasars with black hole masses measured with RM. This work constitutes the first large sample of C IV RM measurements in more than a dozen quasars, demonstrating the utility of multiobject RM campaigns.

Keywords: Supermassive black holes, Reverberation mapping, Active galactic nuclei, Quasars
The Optically Thick Rotating Magnetic Wind from a Massive White Dwarf Merger Product. WD J005311 is a newly identified white dwarf (WD) in a mid-infrared nebula. The spectroscopic observation indicates the existence of a neon-enriched carbon/oxygen wind with a terminal velocity of {v}∞ ,{obs} ∼ 16,000 {km} {{{s}}}-1 and a mass-loss rate of {\dot{M}}obs}∼ 3.5× {10}-6 {M}⊙  {yr}}-1. Here we consistently explain the properties of WD J005311 using a newly constructed wind solution, where the optically thick outflow is launched from the carbon-burning shell on an oxygen-neon core and accelerated by the rotating magnetic field to become supersonic and unbound well below the photosphere. Our model implies that WD J005311 has a mass of M * ∼ 1.1-1.3 M ⊙, a magnetic field of B * ∼ (2-5) × 107 G, and a spin angular frequency of Ω ∼ 0.2-0.5 s-1. The large magnetic field and fast spin support the carbon-oxygen WD merger origin. WD J005311 will neither explode as a type Ia supernova nor collapse into a neutron star. If the wind continues to blow another few kyr, WD J005311 will spin down significantly and join to the known sequence of slowly rotating magnetic WDs. Otherwise it may appear as a fast-spinning magnetic WD and could be a new high-energy source.

Keywords: Stellar rotation, White dwarf stars, Stellar winds
Probing Coronal Magnetic Fields with Sungrazing Comets: H I Lyα from Pickup Ions. Observations of sungrazing comets can be used to probe the solar corona, to study the composition of the comets, and to investigate the plasma processes that govern the interaction between the coronal plasma and cometary gas. UVCS observations of the intensities and line profiles of H I Lyα trace the density, temperature, and outflow speed of the corona. Analysis of H I Lyα observations of comet C/2002 S2 showed a surprising split in the comet’s Lyα tail and an asymmetry of redshifted and blueshifted emission across the tail axis. It was suggested that the velocity structure might result from a population of neutrals produced by charge transfer between pickup ions and cometary neutrals. Here we present numerical simulations of the H I Lyα intensity and velocity centroid for sungrazing comets under the assumptions that the magnetic field and solar wind are radial. The models qualitatively reproduce the observations of Comet C/2002 S2 and potentially explain the split tail morphology that was seen in C/2002 S2 and also C/2001 C2. They also match the observed red- and blueshifts, though the solar wind velocity needed to explain the blueshift implies strong Doppler dimming and requires a higher outgassing rate to match the light curve. However, the models do not match the observations in detail, and we discuss the remaining discrepancies and the uncertainties in the model. We briefly discuss the implications for other UVCS comet observations and sungrazing comet observations with the Metis coronagraph.

Keywords: Slow solar wind, Comets, Solar corona
Is the SNR HESS J1731-347 Colliding with Molecular Clouds?. The supernova remnant HESS J1731-347 is a young supernova remnant (SNR) that displays a nonthermal X-ray and TeV shell structure. A molecular cloud at a distance of ∼3.2 kpc is spatially coincident with the western part of the SNR, and it was likely hit by the SNR. The X-ray emission from this part of the shell is much lower than from the rest of the SNR. Moreover, a compact GeV emission region coincident with the cloud has been detected with a soft spectrum. These observations seem to imply a shock-cloud collision scenario at this area, where the stalled shock can no longer accelerate super-TeV electrons or maintain strong magnetic turbulence downstream, while the GeV cosmic rays (CRs) are released through this stalled shock. To test this hypothesis, we have performed a detailed Fermi-LAT reanalysis of the HESS J1731-347 region with over nine years of data. Two distinct GeV components are found, one displaying a soft spectrum is from the compact GeV emission region, the other one displaying a hard spectrum is from the rest of the SNR (excluding the cloud region). A hadronic model involving a shock-cloud collision scenario is built to explain the γ-ray emission from this area. It consists of three CR sources: run-away super-TeV CRs that have escaped from the fast shock, leaked GeV CRs from the stalled shock, and the local CR sea. The X-ray and γ-ray emission of the SNR excluding the shock-cloud interaction region is explained in a one-zone leptonic model. Our shock-cloud collision model explains the GeV-TeV observations from the clouds around HESS J1731-347, i.e., a cloud in contact with the SNR and a distant cloud in spatial coincidence to the TeV source HESS J1729-345. We find however that the leaked GeV CRs from the shock-cloud collision do not necessarily dominate the GeV emission from the clouds, due to a comparable contribution from the local CR sea.

Keywords: Galactic cosmic rays, Supernova remnants, Gamma-rays, Molecular clouds
New Constraints on the Nuclear Equation of State from the Thermal Emission of Neutron Stars in Quiescent Low-mass X-Ray Binaries. This paper presents a new analysis of the thermal emission from the neutron star (NS) surface to constrain the dense matter equation of state. We employ an empirical parameterization of the equation of state with a Markov Chain Monte Carlo approach to consistently fit the spectra of quiescent low-mass X-ray binaries in globular clusters with well-measured distances. Despite previous analyses predicting low NS radii, we show that it is possible to reconcile the astrophysical data with nuclear physics knowledge with or without including a prior on the slope of the symmetry energy L sym. With this empirical parameterization of the equation of state, we obtain radii of the order of about 12 km without worsening the fit statistic. More importantly, we obtain the following values for the slope of the symmetry energy, its curvature K sym, and the isoscalar skewness parameter Q sat: {L}sym}={37.2}-8.9+9.2 MeV, {K}sym}=-{85}-70+82 MeV, and {Q}sat}={318}-366+673 MeV. These are the first measurements of the empirical parameters K sym and Q sat. Their values are only weakly impacted by our assumptions, such as the distances or the number of free empirical parameters, provided the latter are taken within a reasonable range. We also study the weak sensitivity of our results to the set of sources analyzed, and we identify a group of sources that dominates the constraints. The resulting masses and radii obtained from this empirical parameterization are also compared to other measurements from electromagnetic observations of NSs and gravitational wave signals from the NS-NS merger GW170817.

Keywords: Low-mass x-ray binary stars, Neutron stars, Nuclear physics