Sazuna/UAT_keywords huggingface dataset:
Narrowband Large Amplitude Whistler-mode Waves in the Solar Wind and Their Association with Electrons: STEREO Waveform Capture Observations. Large amplitude (up to 70 mV m-1) whistler-mode waves at frequencies of ∼0.2-0.4 fce (electron cyclotron frequency) are frequently observed in the solar wind. The waves are obliquely propagating at angles close to the resonance cone, resulting in significant electric fields parallel to the background magnetic field, enabling strong interactions with solar wind electrons. Very narrowband (sinusoidal waveforms) and less coherent waves (more irregular waveforms) occur, but do not have a bimodal distribution. Frequencies and/or propagation angles are distinctly different from whistler-mode waves usually observed in the solar wind, and amplitudes are 1-3 orders of magnitude larger. Waves occur most often in association with stream interaction regions, and are often "close-packed." Wave occurrence as a function of normalized electron heat flux and beta is consistent with the whistler heat flux fan instability for both the narrowband coherent and the incoherent waves. The incoherent waves are associated with zero or near zero heat flux. This suggests that the less coherent waves may be more effective in regulating the electron heat flux, or that the scattering and energization of solar wind electrons by the narrowband waves results in broadening of the waves. The oblique propagation and large amplitudes of both the narrowband and less coherent whistlers enable resonant interactions with electrons over a broad energy range, and, unlike parallel whistlers, do not require that the electrons and waves counter-propagate. Therefore, they are much more effective in modifying solar wind electron distributions than parallel propagating waves.

Keywords: Space plasmas, Plasma physics, Interplanetary turbulence, Solar wind, Plasma astrophysics, Corotating streams, Interplanetary physics
Cosmology-independent Estimate of the Hubble Constant and Spatial Curvature using Time-delay Lenses and Quasars. With the distance sum rule in the Friedmann-Lemaître-Robertson-Walker metric, model-independent constraints on both the Hubble constant H0 and spatial curvature ${{\rm{\Omega }}}_{K}$ can be obtained using strong lensing time-delay data and Type Ia supernovae (SNe Ia) luminosity distances. This method is limited by the relatively low redshifts of SNe Ia, however. Here, we propose using quasars as distance indicators, extending the coverage to encompass the redshift range of strong lensing systems. We provide a novel and improved method of determining H0 and ${{\rm{\Omega }}}_{K}$ simultaneously. By applying this technique to the time-delay measurements of seven strong lensing systems and the known ultraviolet versus X-ray luminosity correlation of quasars, we constrain the possible values of both H0 and ${{\rm{\Omega }}}_{K}$ , and find that ${H}_{0}={75.3}_{-2.9}^{+3.0}$ km ${{\rm{s}}}^{-1}\,{\mathrm{Mpc}}^{-1}$ and ${{\rm{\Omega }}}_{K}=-{0.01}_{-0.17}^{+0.18}$ . The measured ${{\rm{\Omega }}}_{K}$ is consistent with zero spatial curvature, indicating that there is no significant deviation from a flat universe. If we use flatness as a prior, we infer that ${H}_{0}={75.3}_{-1.9}^{+1.9}$ km ${{\rm{s}}}^{-1}\,{\mathrm{Mpc}}^{-1}$ , representing a precision of 2.5%. If we further combine these data with the 1048 current Pantheon SNe Ia, our model-independent constraints can be further improved to ${H}_{0}={75.3}_{-2.9}^{+3.0}$ km ${{\rm{s}}}^{-1}\,{\mathrm{Mpc}}^{-1}$ and ${{\rm{\Omega }}}_{K}={0.05}_{-0.14}^{+0.16}$ . In every case, we find that the Hubble constant measured with this technique is strongly consistent with the value (∼74 km ${{\rm{s}}}^{-1}\,{\mathrm{Mpc}}^{-1}$ ) measured using the local distance ladder, as opposed to the value optimized by Planck.

Keywords: Quasars, Cosmological parameters, Strong gravitational lensing, Observational cosmology, Distance indicators, Hubble constant, Type Ia supernovae
Caltech-NRAO Stripe 82 Survey (CNSS). IV. The Birth of Radio-loud Quasar 013815+00. It is believed that the gas accretion onto supermassive black holes is the main process of powering this quasar's luminous emission, which occurs in optical, UV, and X-ray regimes and less frequently in radio waves. The observational fact that only a few percent of quasars are radio-loud is still an unresolved issue concerning the understanding of the active galactic nucleus (AGN) population. Here we present a detection of a rapid transition from the radio-quiet to the radio-loud mode in quasar 013815+00 (z = 0.94) which coincides with changes of its UV-optical continuum and the low ionization Mg II broadline. We interpret this as an enhancement of accretion onto a central black hole of about 109 solar masses. As a consequence a new radio-loud AGN was born. Its spectral and morphological properties indicate that it went through the short gigahertz-peaked spectrum phase at the beginning of its activity and has now stabilized its flux density at the level of a few millijansky. The radio morphology of 013815+00 is very compact and we predict that with such short-term jet activity its development will be very slow. The observed luminosity changes of the accretion disk are shorter than the lifetime of the new radio phase in 013815+00.

Keywords: Radio active galactic nuclei, Active galactic nuclei
Multiwavelength Observations of 2HWC J1928+177: Dark Accelerator or New TeV Gamma-Ray Binary?. 2HWC J1928+177 is a Galactic TeV gamma-ray source detected by the High Altitude Water Cherenkov (HAWC) Observatory up to ∼56 TeV. The HAWC source, later confirmed by the High Energy Stereoscopic System, still remains unidentified as a dark accelerator since there is no apparent supernova remnant or pulsar wind nebula detected in the lower-energy bands. The radio pulsar PSR J1928+1746, coinciding with the HAWC source position, has no X-ray counterpart. Our SED modeling shows that inverse Compton scattering in the putative pulsar wind nebula can account for the TeV emission only if the unseen nebula is extended beyond $r\sim 4^{\prime} $ . Alternatively, TeV gamma-rays may be produced by hadronic interactions between relativistic protons from an undetected supernova remnant associated with the radio pulsar and a nearby molecular cloud G52.9+0.1. NuSTAR and Chandra observations detected a variable X-ray point source within the HAWC error circle, potentially associated with a bright infrared (IR) source. The X-ray spectra can be fitted with an absorbed power-law model with NH = (9 ± 3) × 1022 cm-2 and ΓX = 1.6 ± 0.3 and exhibit long-term X-ray flux variability over the last decade. If the X-ray source, possibly associated with the IR source (likely an O star), is the counterpart of the HAWC source, it may be a new TeV gamma-ray binary powered by collisions between the pulsar wind and stellar wind. Follow-up X-ray observations are warranted to search for diffuse X-ray emission and determine the nature of the HAWC source.

Keywords: X-ray astronomy, Gamma-ray sources, High mass x-ray binary stars, Gamma-ray telescopes, Supernova remnants, Non-thermal radiation sources, Interstellar medium, X-ray sources, Gamma-ray astronomy, Radio pulsars
Common Envelope Wind Tunnel: The Effects of Binary Mass Ratio and Implications for the Accretion-driven Growth of LIGO Binary Black Holes. We present three-dimensional local hydrodynamic simulations of flows around objects embedded within stellar envelopes using a "wind tunnel" formalism. Our simulations model the common envelope dynamical inspiral phase in binary star systems in terms of dimensionless flow characteristics. We present suites of simulations that study the effects of varying the binary mass ratio, stellar structure, equation of state, relative Mach number of the object's motion through the gas, and density gradients across the gravitational focusing scale. For each model, we measure coefficients of accretion and drag experienced by the embedded object. These coefficients regulate the coupled evolution of the object's masses and orbital tightening during the dynamical inspiral phase of the common envelope. We extrapolate our simulation results to accreting black holes with masses comparable to that of the population of LIGO black holes. We demonstrate that the mass and spin accrued by these black holes per unit orbital tightening are directly related to the ratio of accretion to drag coefficients. We thus infer that the mass and dimensionless spin of initially nonrotating black holes change by of order 1% and 0.05, respectively, in a typical example scenario. Our prediction that the masses and spins of black holes remain largely unmodified by a common envelope phase aids in the interpretation of the properties of the growing observed population of merging binary black holes. Even if these black holes passed through a common envelope phase during their assembly, features of mass and spin imparted by previous evolutionary epochs should be preserved.

Keywords: Accretion, Hydrodynamical simulations, Hydrodynamics, Close binary stars, Common envelope binary stars
Morphological and Spectral Study of 4FGL J1115.1-6118 in the Region of the Young Massive Stellar Cluster NGC 3603. We report a detailed study of an unidentified gamma-ray source located in the region of the compact stellar cluster NGC 3603. This is a star-forming region (SFR) powered by a massive cluster of OB stars. A dedicated analysis of about 10 yr of data from 10 GeV to 1 TeV, provided by the Large Area Telescope on board the Fermi Gamma-ray Space Telescope, yields the detection of a pointlike source at a significance of 9σ. The source photon spectrum can be described by a power-law model with a best-fit spectral index of 2.35 ± 0.03. In addition, the analysis of a deep Chandra image in the 0.5-7 keV band reliably rules out an extragalactic origin for the gamma-rays. We also conclude that the broadband spectral energy distribution of the point source can be explained well with both leptonic and hadronic models. No firm evidence of association with any other classes of known gamma-ray emitters is found; therefore, we speculate that 4FGL J1115.1-6118 is a gamma-ray-emitting SFR.

Keywords: High energy astrophysics, Gamma-ray sources, Star forming regions, Young massive clusters, Galactic cosmic rays, Non-thermal radiation sources, X-ray sources, Space telescopes, Gamma-ray astronomy, Gamma-rays, Star clusters
Formulating and Critically Examining the Assumptions of Global 21 cm Signal Analyses: How to Avoid the False Troughs That Can Appear in Single-spectrum Fits. The assumptions inherent to global 21 cm signal analyses are rarely delineated. In this paper, we formulate a general list of suppositions underlying a given claimed detection of the global 21 cm signal. Then, we specify the form of these assumptions for two different analyses: (1) the one performed by the team for the Experiment to Detect the Global Epoch-of-Reionization Signature (EDGES) showing an absorption trough in brightness temperature that they modeled separately from the sky foreground and (2) a new, so-called minimum assumption analysis (MAA) that makes the most conservative assumptions possible for the signal. We show fits using the EDGES analysis on various beam-weighted foreground simulations from the EDGES latitude with no signal added. Depending on the beam used, these simulations produce large false troughs because of the invalidity of the foreground model in describing the combination of beam chromaticity and the shape of the Galactic plane in the sky, the residuals of which are captured by the ad hoc flattened Gaussian signal model. On the other hand, the MAA provides robust fits by including many spectra at different time bins and allowing any possible 21 cm spectrum to be modeled exactly. We present uncertainty levels and example signal reconstructions found with the MAA for different numbers of time bins. With enough time bins, one can determine the true 21 cm signal with the MAA to &lt;10 times the noise level.

Keywords: Reionization, Astronomy data analysis, Computational methods
Cosmicflows-3: The South Pole Wall. Velocity and density field reconstructions of the volume of the universe within 0.05c derived from the Cosmicflows-3 catalog of galaxy distances has revealed the presence of a filamentary structure extending across ∼0.11c. The structure, at a characteristic redshift of 12,000 km s-1, has a density peak coincident with the celestial South Pole. This structure, the largest contiguous feature in the local volume and comparable to the Sloan Great Wall at half the distance, is given the name the South Pole Wall.

Keywords: Cosmology, Large-scale structure of the universe
The Streamer Blowout Origin of a Flux Rope and Energetic Particle Event Observed by Parker Solar Probe at 0.5 au. The distribution of spacecraft in the inner heliosphere during 2019 March enabled comprehensive observations of an interplanetary coronal mass ejection (ICME) that encountered Parker Solar Probe (PSP) at 0.547 au from the Sun. This ICME originated as a slow (∼311 km s-1) streamer blowout (SBO) on the Sun as measured by the white-light coronagraphs on board the Solar TErrestrial RElations Observatory-A and the Solar and Heliospheric Observatory. Despite its low initial speed, the passage of the ICME at PSP was preceded by an anisotropic, energetic (≲100 keV/n) ion enhancement and by two interplanetary shocks. The ICME was embedded between slow (∼300 km s-1) solar wind and a following, relatively high-speed (∼500 km s-1), stream that most likely was responsible for the unexpectedly short (based on the SBO speed) ICME transit time of less than ∼56 hr between the Sun and PSP, and for the formation of the preceding shocks. By assuming a graduated cylindrical shell (GCS) model for the SBO that expands self-similarly with time, we estimate the propagation direction and morphology of the SBO near the Sun. We reconstruct the flux-rope structure of the in situ ICME assuming an elliptic-cylindrical topology and compare it with the portion of the 3D flux-rope GCS morphology intercepted by PSP. ADAPT-WSA-ENLIL-Cone magnetohydrodynamic simulations are used to illustrate the ICME propagation in a structured background solar wind and estimate the time when PSP established magnetic connection with the compressed region that formed in front of the ICME. This time is consistent with the arrival at PSP of energetic particles accelerated upstream of the ICME.

Keywords: Ejecta, Solar energetic particles, Solar coronal mass ejection shocks, Interplanetary particle acceleration, Solar coronal mass ejections
Galactic Center IRS 13E: Colliding Stellar Winds or an Intermediate-mass Black Hole?. A small cluster of massive stars residing in the Galactic center, collectively known as IRS 13E, is of special interest due to its close proximity to the central supermassive black hole Sgr A* and the possibility that an embedded intermediate-mass black hole (IMBH) binds its member stars. It has been suggested that colliding winds from two member stars, both classified as Wolf-Rayet type, are responsible for the observed X-ray, infrared, and radio emission from IRS 13E. We have conducted an in-depth study of the X-ray spatial, temporal, and spectral properties of IRS 13E, based on 5.6 Ms of ultradeep Chandra observations obtained over 20 years. These X-ray observations show no significant evidence for source variability. We have also explored the kinematics of the cluster members, using Keck near-infrared imaging and spectroscopic data on a 14 yr baseline that considerably improve the accuracy of the stars' proper motions. The observations are interpreted using three-dimensional hydrodynamical simulations of colliding winds tailored to match the physical conditions of IRS 13E, leading us to conclude that the observed X-ray spectrum and morphology can be well explained by the colliding wind scenario, in the meantime offering no support for the presence of a putative IMBH. An IMBH more massive than a few 103 M⊙ is also strongly disfavored by the stellar kinematics.

Keywords: Black hole physics, Stellar winds, Galactic center, X-ray sources
The High-mass Protostellar Population of a Massive Infrared Dark Cloud. We conduct a census of the high-mass protostellar population of the ∼70,000 M⊙ infrared dark cloud (IRDC) G028.37+00.07, identifying 35 sources based on their 70 μm emission, as reported in the Herschel Hi-GAL catalog of Molinari et al. We perform aperture photometry to construct spectral energy distributions, which are then fit with the massive protostar models of Zhang &amp; Tan. We find that the sources span a range of isotropic luminosities from ∼20 to 4500 L⊙. The most luminous sources are predicted to have current protostellar masses of m* ∼ 10 M⊙ forming from cores of mass Mc ∼ 40 to 400 M⊙. The least luminous sources in our sample are predicted to be protostars with masses as low as ∼0.5 M⊙ forming from cores with Mc ∼ 10 M⊙, which are the minimum values explored in the protostellar model grid. The detected protostellar population has a total estimated protostellar mass of M* ∼ 100 M⊙. Allowing for completeness corrections, which are constrained by comparison with an ALMA study in part of the cloud, we estimate a star formation efficiency per freefall time of ∼3% in the IRDC. Finally, analyzing the spatial distribution of the sources, we find relatively low degrees of central concentration of the protostars. The protostars, including the most massive ones, do not appear to be especially centrally concentrated in the protocluster as defined by the IRDC boundary.

Keywords: Protostars, Star formation, Infrared photometry
Kinetic-scale Flux Rope in the Magnetosheath Boundary Layer. We here present a new type of kinetic-scale (∼1 ion gyroradius) flux rope (KFR) in the Earth's dayside magnetosheath boundary layer with Magnetospheric Multiscale high temporal cadence data. This structure exhibits a slight twist of magnetic field that is possibly generated by a field-aligned current, which differs from typical dayside flux ropes usually observed within the current sheet where magnetic reconnection can occur. The perpendicular electron fluxes within 19-52 eV are increased ∼10% inside the KFR. Detailed analysis shows that these perpendicular electrons may encounter their mirror point (at the position of the KFR, strong field region) when traveling from the magnetosheath toward the ionosphere and will be reflected to the magnetosheath. A possible scenario is that this KFR is different from previous flux ropes that transfer electron flux to the magnetosphere but could intercept magnetosheath large pitch angle electron flux to the magnetosphere.

Keywords: Space plasmas, Magnetohydrodynamics, Geomagnetic fields, Plasma physics, Planetary magnetospheres
Distance to the Energetic Neutral Hydrogen Source from the Heliotail. The interaction of the solar wind (SW) with the partially ionized interstellar medium forms the heliosphere. As the supersonic SW flows away from the Sun and incorporates pickup ions (PUIs), they are slowed, compressed, and heated at a termination shock, creating an energetic ion population in the inner heliosheath. The neutralization of PUIs in the heliosheath creates energetic neutral atoms (ENAs) at ∼keV energies that travel ballistically and can be observed at 1 au by the Interstellar Boundary Explorer (IBEX). IBEX uses single-pixel cameras to map ENAs from the heliosphere. In this study, we analyze IBEX observations of &gt;1 keV ENAs from the heliotail during 2009-2017. The ENA spectral index maximizes near the ecliptic plane and decreases at higher latitudes, reflecting the latitudinal structure of the SW. We show that the angular spread of this structure can be used to derive the distance at which the observed ENAs originate, I.e., their cooling length. Using Ulysses observations of the SW we determine that the distance from the Sun to the source of ∼1-6 keV ENAs in the heliotail is ≥289 ± 35 au in 2009-2013 and ≥489 ± 56 au in 2014-2017, using the distance to the termination shock in the downwind direction as 160 au based on the analysis of McComas et al. The increase in ENA source distance over time suggests that IBEX is observing a fast/hotter plasma parcel propagating down the heliotail before being replaced by slow/cooler plasma as the solar cycle evolves.

Keywords: Solar cycle, Heliosphere, Solar wind, Pickup ions, Interstellar medium, Charge exchange ionization, Heliosheath
THEMIS: A Parameter Estimation Framework for the Event Horizon Telescope. The Event Horizon Telescope (EHT) provides the unprecedented ability to directly resolve the structure and dynamics of black hole emission regions on scales smaller than their horizons. This has the potential to critically probe the mechanisms by which black holes accrete and launch outflows, and the structure of supermassive black hole spacetimes. However, accessing this information is a formidable analysis challenge for two reasons. First, the EHT natively produces a variety of data types that encode information about the image structure in nontrivial ways; these are subject to a variety of systematic effects associated with very long baseline interferometry and are supplemented by a wide variety of auxiliary data on the primary EHT targets from decades of other observations. Second, models of the emission regions and their interaction with the black hole are complex, highly uncertain, and computationally expensive to construct. As a result, the scientific utilization of EHT observations requires a flexible, extensible, and powerful analysis framework. We present such a framework, THEMIS, which defines a set of interfaces between models, data, and sampling algorithms that facilitates future development. We describe the design and currently existing components of THEMIS, how THEMIS has been validated thus far, and present additional analyses made possible by THEMIS that illustrate its capabilities. Importantly, we demonstrate that THEMIS is able to reproduce prior EHT analyses, extend these, and do so in a computationally efficient manner that can efficiently exploit modern high-performance computing facilities. THEMIS has already been used extensively in the scientific analysis and interpretation of the first EHT observations of M87.

Keywords: Galactic center, Very long baseline interferometry, Astronomy data analysis, Submillimeter astronomy, Astrophysical black holes
Polarization of the Cosmic Infrared Background Fluctuations. The cosmic infrared background (CIB) is slightly polarized. Polarization directions of individual galaxies could be aligned with tidal fields around galaxies, resulting in nonzero CIB polarization. We use a linear intrinsic alignment model to theoretically predict angular correlations of the CIB polarization fluctuations and find that electriclike and curl-like (B-mode) polarization modes are equally generated with power four orders of magnitude less than their intensity. The CIB B-mode signal is negligible and not a concerning foreground for the inflationary B-mode searches at nominal frequencies for cosmic microwave background measurements, but could be detected at submillimeter wavelengths by future space missions.

Keywords: Cosmic inflation, Infrared galaxies, Cosmic background radiation