Sazuna/UAT_keywords huggingface dataset:
Turbulent Model of Crab Nebula Radiation. We construct a turbulent model of the Crab Nebula's nonthermal emission. The present model resolves a number of long-standing problems of the Kennel-Coroniti model: (I) the sigma problem, (II) the hard spectrum of radio electrons, (III) the high peak energy of gamma-ray flares, (IV) and the spatial evolution of the infrared (IR) emission. The Nebula contains two populations of injected particles: Component-I, accelerated at the wind termination shock via the Fermi-I mechanism; and Component-II, accelerated in reconnecting turbulence in highly magnetized (σ ≫ 1) plasma in the central part of the Crab Nebula. The reconnecting turbulence in Component-II extends from radio to gamma-rays: it accelerates radio electrons with a hard spectrum, destroys the large-scale magnetic flux (and thus resolves the sigma problem), and occasionally produces gamma-ray flares (from the largest-scale reconnection events). The model reproduces the broadband spectrum of the Crab Nebula, from low-frequency synchrotron emission in radio to inverse-Compton emission at TeV energies, as well as the spatially resolved evolution of the spectral indices in the IR and optical bands.

Keywords: Interstellar synchrotron emission, Rotation powered pulsars, Stellar wind bubbles
Photochemistry of Anoxic Abiotic Habitable Planet Atmospheres: Impact of New H<SUB>2</SUB>O Cross Sections. We present a study of the photochemistry of abiotic habitable planets with anoxic CO2-N2 atmospheres. Such worlds are representative of early Earth, Mars, and Venus and analogous exoplanets. Photodissociation of H2O controls the atmospheric photochemistry of these worlds through production of reactive OH, which dominates the removal of atmospheric trace gases. The near-UV (NUV; &gt;200 nm) absorption cross sections of H2O play an outsized role in OH production; these cross sections were heretofore unmeasured at habitable temperatures (&lt;373 K). We present the first measurements of NUV H2O absorption at 292 K and show it to absorb orders of magnitude more than previously assumed. To explore the implications of these new cross sections, we employ a photochemical model; we first intercompare it with two others and resolve past literature disagreement. The enhanced OH production due to these higher cross sections leads to efficient recombination of CO and O2, suppressing both by orders of magnitude relative to past predictions and eliminating the low-outgassing "false-positive" scenario for O2 as a biosignature around solar-type stars. Enhanced [OH] increases rainout of reductants to the surface, relevant to prebiotic chemistry, and may also suppress CH4 and H2; the latter depends on whether burial of reductants is inhibited on the underlying planet, as is argued for abiotic worlds. While we focus on CO2-rich worlds, our results are relevant to anoxic planets in general. Overall, our work advances the state of the art of photochemical models by providing crucial new H2O cross sections and resolving past disagreement in the literature and suggests that detection of spectrally active trace gases like CO in rocky exoplanet atmospheres may be more challenging than previously considered.

Keywords: Planetary theory, Exoplanet atmospheric composition , Extrasolar rocky planets, Water vapor, Planetary atmospheres, Habitable planets, Exoplanet atmospheres
Study of the Influence of the Solar Wind Energy on the Geomagnetic Activity for Space Weather Science. This paper addresses the investigation of the interaction of the solar wind energy with the Earth's magnetosphere, by studying its correlation with the disturbance storm time (Dst) index, a proxy of the geomagnetic activity. Some relevant parameters of the solar wind (the bulk speed and the z-component of the interplanetary magnetic field) are explored in the energy-Dst space. It results that (I) the solar wind energy and the geomagnetic activity are strictly related, with the coronal mass ejections representing the most energetic and geoeffective driver; (II) the slow solar wind has negligible effects on Earth regardless of its energy content, whereas high-speed streams may induce severe geomagnetic storming depending on the advected energy; and (III) while at low and mid energies, geomagnetic disturbances are induced provided the magnetic reconnection between the interplanetary and terrestrial magnetic fields occurs, high-energy solar wind plasma can impact Earth even without reconnecting with the geomagnetic field at the dayside magnetopause. The most significant result in the framework of space weather science resides in the observational evidence that the Earth's magnetosphere has a maximum response to the energetic content of the solar wind, which leads to the derivation of an empirical law allowing the proper forecast of the upper limit of the intensity of any geomagnetic disturbance on the basis of the solar wind energy derived in situ at the Lagrangian point L1.

Keywords: Magnetohydrodynamics, Heliosphere, Space weather, Solar wind, Solar-terrestrial interactions
Spatial Distribution of the Origin of Umbral Waves in a Sunspot Umbra. Umbral flashes (UFs) are emissions in the core of chromospheric lines caused by upward propagating waves steepening into shocks. UFs are followed by an expanding blueshifted umbral wave and redshifted plasma returning to the initial state. Here we use 5 s cadence images acquired at ±0.04 nm off the H ${}_{\alpha }$ line center by the Visible Imaging Spectrometer installed on the Goode Solar Telescope (GST) to detect the origin of UFs and umbral waves (UWs) in a sunspot with a uniform umbra free of light bridges and clusters of umbral dots. The data showed that UFs do not randomly originate over the umbra. Instead, they appear to be repeatedly triggered at locations with the lowest umbral intensity and the most powerful oscillations of H ${}_{\alpha }$ -0.04 nm intensity. GST magnetic field measurements using the Near-Infrared Imaging Spectropolarimeter also showed that the dominant location of prevalent UF origin is cospatial associated with the strongest fields in the umbra. Interface Region Imaging Spectrograph 149.0 nm images showed that no bright UV loops were anchored in the umbra in general, and near the UF patches in particular, suggesting that UFs and UWs alone cannot be responsible for the origin of warm coronal loops. We thus conclude that the existence of locations with prevalent origin of UFs confirms the idea that they may be driven by a subsurface source located near the axis of a flux rope, while the presence of several UFs trigger centers may indicate the complex structure of a sunspot umbra.

Keywords: Sunspots, Solar photosphere, Solar chromosphere
Survey of Extremely High-velocity Outflows in Sloan Digital Sky Survey Quasars. We present a survey of extremely high-velocity outflows (EHVOs) in quasars, defined by speeds between 0.1c and 0.2c. This region of parameter space has not been included in previous surveys, but it might present the biggest challenge for theoretical models and it might be a large contributor to feedback due to the outflows' potentially large kinetic power. Using the Sloan Digital Sky Survey, we find 40 quasar spectra with broad EHVO C IV absorption, 10 times more than the number of previously known cases. We characterize the EHVO absorption and find that in 26 cases, C IV is accompanied by N V and/or O VI absorption. We find that EHVO quasars lack He II emission and have overall larger bolometric luminosities and black hole masses than those of their parent sample and broad absorption line quasars (BALQSOs), while we do not find significant differences in their Eddington ratios. We also report a trend toward larger black hole masses as the velocity of the outflowing gas increases in the BALQSOs in our sample. The overall larger Lbol and lack of He II emission of EHVO quasars suggest that radiation is likely driving these outflows. We find a potential evolutionary effect as EHVO quasars seem to be more predominant at large redshifts. We estimate that the kinetic power of these outflows may be similar to or even larger than that of the outflows from BALQSOs as the velocity factor increases this parameter by 1-2.5 orders of magnitude. Further study of EHVO quasars will help improve our understanding of quasar physics.

Keywords: Radio quiet quasars, Active galactic nuclei, Broad-absorption line quasar, Quasars
Effect of Binarity in Star Cluster Dynamical Mass Determination. In this paper we explore the effects that the presence of a fraction of binary stars has in the determination of a star cluster mass via the virial theorem. To reach this aim in an accurate and consistent way, we run a set of simulations using the direct summation, high precision, code NBODY7. By means of this suite of simulations we are able to quantify the overestimate of open-star-cluster-like models' dynamical masses when making a straight application of the virial theorem using available position and radial velocity measurements. The mass inflation caused by the binary "heating" contribution to the measured velocity dispersion depends, of course, on the initial binary fraction, fb0 and its following dynamical evolution. For an fb (evolved up to 1.5 Gyr) in the range 8%-42% the overestimate of the mass done using experimentally sounding estimates for the velocity dispersion can be up to a factor of 45. We provide a useful fitting formula to correct the dynamical mass determination for the presence of binaries, and underline how neglecting the role of binaries in stellar systems might lead to erroneous conclusions about their total mass budget. If this trend remains valid for larger systems like dwarf spheroidal galaxies, which are still far out of reach for high-precision dynamical simulations taking their binaries into account, it would imply an incorrect overestimation of their dark matter content, as inferred by means of available velocity dispersion measurements.

Keywords: Binary stars, N-body simulations, Star clusters
ACRONYM IV: Three New, Young, Low-mass Spectroscopic Binaries. As part of our search for new low-mass members of nearby young moving groups (YMGs), we discovered three low-mass, spectroscopic binaries, two of which are not kinematically associated with any known YMG. Using high-resolution optical spectroscopy, we measure the component and systemic radial velocities of the systems, as well as their lithium absorption and Hα emission, both spectroscopic indicators of youth. One system (2MASS J02543316-5108313, M2.0+M3.0) we confirm as a member of the 40 Myr old Tuc-Hor moving group, but whose binarity was previously undetected. The second young binary (2MASS J08355977-3042306, K5.5+M1.5) is not a kinematic match to any known YMG, but each component exhibits lithium absorption and strong and wide Hα emission indicative of active accretion, setting an upper age limit of 15 Myr. The third system (2MASS J10260210-4105537, M1.0+M3.0) has been hypothesized in the literature to be a member of the 10 Myr old TW Hya Association, but our measured systemic velocity shows the binary is in fact not part of any known YMG. This last system also has lithium absorption in each component, and has strong and variable Hα emission, setting an upper age limit of 15 Myr based on the lithium detection.

Keywords: M dwarf stars, High resolution spectroscopy, Stellar kinematics, Radial velocity, Spectroscopic binary stars, Stellar classification, Pre-main sequence stars, Low mass stars, K dwarf stars, Stellar associations, Stellar evolution
IRIS Si IV Line Profiles at Flare Ribbons as Indications of Chromospheric Condensation. We present temporal variations of the Si IV line profiles at the flare ribbons in three solar flares observed by the Interface Region Imaging Spectrograph. In the M1.1 flare on 2014 September 6 and the X1.6 flare on 2014 September 10, the Si IV line profiles evolve from wholly redshifted to red-wing enhanced with the flare development. However, in the B1.8 flare on 2016 December 2, the Si IV line profiles are wholly redshifted throughout the flare evolution. We fit the wholly redshifted line profiles with a single-Gaussian function, but fit the red-asymmetric ones with a double-Gaussian function to deduce the corresponding Doppler velocities. In addition, we find that hard X-ray emission above 25 keV shows up in the two large flares, implying a nonthermal electron beam heating. In the microflare, there only appears weak hard X-ray emission up to 12 keV, indicative of a mostly thermal heating. We interpret the redshifts or red asymmetries of the Si IV line at the ribbons in the three flares as spectral manifestations of chromospheric condensation. We propose that whether the line appears to be wholly redshifted or red-asymmetric depends on the heating mechanisms, as well as on the propagation of the condensation.

Keywords: Solar flare spectra, Solar flares, Solar ultraviolet emission, Solar transition region
Electron Density Reconstruction of Solar Coronal Mass Ejections Based on a Genetic Algorithm: Method and Application. We present a new method to reconstruct the three-dimensional electron density of coronal mass ejections (CMEs) based on a genetic algorithm, namely the genetic reconstruction method (GRM). GRM is first applied to model CMEs with different orientations and shapes. A set of analytic model CMEs from Gibson and Low is employed to produce synthetic CME images for GRM reconstruction. Model CMEs with longitudes of 0°, 45°, 90°, 135°, and 180° and latitudes of 0°, 15°, 30°, and 45° are used to test the performance of GRM. The model CMEs are obscured with a simulated occulter of a coronagraph to determine the influence of CME brightness incompleteness. We add random noise to some synthetic CME images to test the performance of GRM. The CME reconstructions are carried out using synthetic data from Solar Terrestrial Relations Observatory (STEREO) A and B with a separation angle of 90° and from STEREO A and the Solar and Heliospheric Observatory (SOHO) with a separation angle of 73°. The Pearson correlation coefficient and the mean relative absolute deviation are calculated to analyze the similarities in brightness and electron density between the model and reconstructed CMEs. Comparisons based on the similarity analysis under various conditions stated above give us valuable insights into the advantages and limitations of GRM reconstruction. The method is then applied to real coronagraph data from STEREO A and B, and SOHO on 2013 September 30.

Keywords: Solar activity, Line of sight, Solar coronal mass ejections, Field of view
Spectroscopically Confirmed Lyα Emitters from Redshift 5 to 7 behind 10 Galaxy Cluster Lenses. We present 36 spectroscopically confirmed intrinsically UV-faint Lyα-emitting galaxies from follow-up observations with Keck/DEep Imaging Multi-Object Spectrograph of gravitationally lensed high-redshift candidates. Candidates were selected to be between 5 ≲ z ≲ 7 from photometric data using Hubble Space Telescope and Spitzer imaging surveys. We performed an integrated photometric redshift probability cut &gt;1% between 5 &lt; z &lt; 7 to construct a sample of 198 high-redshift objects. Our sample spans intrinsic UV luminosities from a few L* down to 0.001L*. We identified 19 high-confidence detections and 17 likely detections of Lyα. We divided our sample into lower-redshift (z ∼ 5.5) and higher-redshift (z ∼ 6.5) bins and ran Monte Carlo trials, incorporating the strengths of the Lyα emission and the photometric redshifts of the nondetections. Considering only objects where Lyα could be detected at EW(Lyα) &gt; 25 Å at 3σ at the fiducial depth of our survey, and only those galaxies with EW(Lyα) &gt; 25 Å, and only objects with mAB &lt; 26.8, we found the Lyα emitter (LAE) fraction to be flat or modestly increase from 0.26 ± 0.04 to 0.30 ± 0.04. These values are consistent with a rising LAE fraction with redshift out to z ∼ 6, but at z ∼ 6.5, there is some tension between our results and results from surveys at intrinsically brighter luminosities. We conclude that intrinsically fainter galaxies have Lyα emission, and there is a steep drop in the LAE fraction from our high-redshift sample at z ∼ 6.5 and from similar galaxies at z ∼ 7.5. This likely indicates we are witnessing the tail end of the epoch of reionization, as such a drop is not expected due to changes of intrinsic galaxy properties between these redshifts.

Keywords: Cosmology, Galaxy evolution, Spectroscopy, Lyman-alpha galaxies, Reionization, High-redshift galaxies
Magnetic Field Structure of Orion Source I. We observed polarization of the SiO rotational transitions from Orion Source I (SrcI) to probe the magnetic field in bipolar outflows from this high-mass protostar. Both 43 GHz J = 1-0 and 86 GHz J = 2-1 lines were mapped with ∼20 au resolution, using the Very Large Array (VLA) and Atacama Large Millimeter/Submillimeter Array (ALMA), respectively. The 28SiO transitions in the ground vibrational state are a mixture of thermal and maser emission. Comparison of the polarization position angles in the J = 1-0 and J = 2-1 transitions allows us to set an upper limit on possible Faraday rotation of 104 rad m-2, which would twist the J = 2-1 position angles typically by less than 10°. The smooth, systematic polarization structure in the outflow lobes suggests a well-ordered magnetic field on scales of a few hundred au. The uniformity of the polarization suggests a field strength of ∼30 mG. It is strong enough to shape the bipolar outflow and possibly lead to sub-Keplerian rotation of gas at the base of the outflow. The strikingly high fractional linear polarizations of 80%-90% in the 28SiO V = 0 masers require anisotropic pumping. We measured circular polarizations of 60% toward the strongest maser feature in the V = 0 J = 1-0 peak. Anisotropic resonant scattering is likely to be responsible for this circular polarization. We also present maps of the 29SiO V = 0 J = 2-1 maser and several other SiO transitions at higher vibrational levels and isotopologues.

Keywords: Stellar jets, Massive stars, Interferometers, Silicon monoxide masers, Star formation, Astrophysical masers, Polarimetry
Early Evolution of Disk, Outflow, and Magnetic Field of Young Stellar Objects: Impact of Dust Model. The formation and early evolution of low-mass young stellar objects (YSOs) are investigated using three-dimensional non-ideal magnetohydrodynamics simulations. We investigate the evolution of YSOs up to $\sim {10}^{4}\,\mathrm{yr}$ after protostar formation, at which protostellar mass reaches $\sim 0.1{M}_{\odot }$ . We particularly focus on the impact of the dust model on the evolution. We found that a circumstellar disk is formed in all simulations, regardless of the dust model. Disk size is approximately 10 au at the protostar formation epoch, and it increases to several tens of au at $\sim {10}^{4}\,\mathrm{yr}$ after protostar formation. The disk mass is comparable to the central protostellar mass, and gravitational instability develops. In simulations with small dust sizes, the warp of the pseudodisk develops $\sim {10}^{4}\,\mathrm{yr}$ after protostar formation. The warp strengthens magnetic braking in the disk and decreases disk size. Ion-neutral drift can occur in the infalling envelope when the typical dust size is $a\gtrsim 0.2\,\mu {\rm{m}}$ and the protostar (plus disk) mass is $M\gtrsim 0.1{M}_{\odot }$ . The outflow activity is anticorrelated to the dust size, and the strong outflow appears with small dust grains.

Keywords: Magnetohydrodynamical simulations, Protoplanetary disks, Circumstellar disks
Testing the Fidelity of Simulations of Black Hole-Galaxy Coevolution at z ∼ 1.5 with Observations. We examine the scaling relations between the mass of a supermassive black hole (SMBH) and its host galaxy properties at 1.2 &lt; z &lt;1.7 using both observational data and simulations. Recent measurements of 32 X-ray-selected, broad-line active galactic nuclei (AGNs) are compared with two independent state-of-the-art efforts, including the hydrodynamic simulation MassiveBlackII (MBII) and a semianalytic model (SAM). After applying an observational selection function to the simulations, we find that both MBII and SAM agree well with the data, in terms of the central distribution. However, the dispersion in the mass ratio between black hole mass and stellar mass is significantly more consistent with the MBII prediction (∼0.3 dex) than with the SAM (∼0.7 dex), even when accounting for observational uncertainties. Hence, our observations can distinguish between the different recipes adopted in the models. The mass relations in the MBII are highly dependent on AGN feedback, while the relations in the SAM are more sensitive to galaxy-merger events triggering nuclear activity. Moreover, the intrinsic scatter in the mass ratio of our high-z sample is comparable with that observed in the local sample, all but ruling out the proposed scenario that the correlations are purely stochastic in nature arising from some sort of cosmic central limit theorem. Our results support the hypothesis of AGN feedback being responsible for a causal link between the SMBH and its host galaxy, resulting in a tight correlation between their respective masses.

Keywords: Active galaxies, Active galactic nuclei, Galaxy evolution
Reflection Features in the X-Ray Spectrum of Fairall 9 and Implications for Tests of General Relativity. X-ray reflection spectroscopy is potentially a powerful tool to probe the spacetime geometry around astrophysical black holes and test general relativity in the strong field regime. However, precision tests of general relativity are only possible if we employ the correct astrophysical model and if we can limit the systematic uncertainties. It is thus crucial to select the sources and the observations most suitable for these tests. In this work, we analyze simultaneous observations of XMM-Newton and NuSTAR of the supermassive black hole in Fairall 9. This source has a number of properties that make it a promising candidate for tests of general relativity using X-ray reflection spectroscopy. Nevertheless, we find that with the available data there is not a unique interpretation of the spectrum of Fairall 9, which prevents, for the moment, the use of this source for robust tests of general relativity. This issue may be solved by future X-ray missions with a higher energy resolution near the iron line.

Keywords: X-ray astronomy, General relativity, Astrophysical black holes
Tidal Asteroseismology: Possible Evidence of Nonlinear Mode Coupling in an Equilibrium State in Kepler Eclipsing Binary KIC 3230227. Previously, a series of tidally-excited oscillations were discovered in the eccentric eclipsing binary KIC 3230227. The pulsation amplitudes and phases suggest the observed oscillations are prograde quadruple modes. In this paper, we refine the analysis and extract more oscillation frequencies. We also study the temporal variations of amplitudes and phases and show that almost all modes have stable phases and amplitudes. We then focus on the non-orbital-harmonic oscillations. We consider two formation mechanisms: (1) nonlinear response of the surface convective layer, and (2) nonlinear three/multi-mode coupling. Although the former can explain some of the observed features, we find the latter mechanism is more probable. Assuming that these are coupled modes, the constant amplitude/phase over four years can be explained by either an equilibrium state in the mode coupling or modes undergoing limit cycles with very long periods. The observed frequency detuning and the calculated damping rates of the daughter modes favor the equilibrium-state interpretation. This is verified by integrating the amplitude equations of three-mode coupling. We find that the steady-state relation derived in Weinberg et al., which relates the observed frequency detuning, phase detuning, and mode damping rates, is approximately satisfied for one mode triplet. We also try to identify the azimuthal number of the modes based on the observed mode amplitude ratios and the selection rules in nonlinear three-mode coupling. We discuss further implications of these observations on nonlinear tidal asteroseismology.

Keywords: Tidal interaction, Asteroseismology, Binary stars