Sazuna/UAT_keywords huggingface dataset:
3D Solar Coronal Loop Reconstructions with Machine Learning. The magnetic field plays an essential role in the initiation and evolution of different solar phenomena in the corona. The structure and evolution of the 3D coronal magnetic field are still not very well known. A way to ascertain the 3D structure of the coronal magnetic field is by performing magnetic field extrapolations from the photosphere to the corona. In previous work, it was shown that by prescribing the 3D-reconstructed loops' geometry, the magnetic field extrapolation produces a solution with a better agreement between the modeled field and the reconstructed loops. This also improves the quality of the field extrapolation. Stereoscopy, which uses at least two view directions, is the traditional method for performing 3D coronal loop reconstruction. When only one vantage point of the coronal loops is available, other 3D reconstruction methods must be applied. Within this work, we present a method for the 3D loop reconstruction based on machine learning. Our purpose for developing this method is to use as many observed coronal loops in space and time for the modeling of the coronal magnetic field. Our results show that we can build machine-learning models that can retrieve 3D loops based only on their projection information. Ultimately, the neural network model will be able to use only 2D information of the coronal loops, identified, traced, and extracted from the extreme-ultraviolet images, for the calculation of their 3D geometry.

Keywords: Solar coronal loops, Convolutional neural networks
Pure Density Evolution of the Ultraviolet Quasar Luminosity Function at 2 ≲ z ≲ 6. The quasar luminosity function (QLF) shows the active galactic nucleus (AGN) demography as a result of the combination of the growth and the evolution of black holes, galaxies, and dark matter halos along the cosmic time. The recent wide and deep surveys have improved the census of high-redshift quasars, making it possible to construct reliable ultraviolet (UV) QLFs at 2 ≲ z ≲ 6 down to M1450 = - 23 mag. By parameterizing these up-to-date observed UV QLFs that are the most extensive in both luminosity and survey area coverage at a given redshift, we show that the UV QLF has a universal shape and its evolution can be approximated by a pure density evolution (PDE). In order to explain the observed QLF, we construct a model QLF employing the halo mass function, a number of empirical scaling relations, and the Eddington ratio distribution. We also include the outshining of AGN over its host galaxy, which made it possible to reproduce a moderately flat shape of the faint end of the observed QLF (slope of ∼ - 1.1). This model successfully explains the observed PDE behavior of UV QLF at z &gt; 2, meaning that the QLF evolution at high redshift can be understood under the framework of halo mass function evolution. The importance of the outshining effect in our model also implies that there could be a hidden population of faint AGNs (M1450 ≳ - 24 mag), which are buried under their host galaxy light.

Keywords: Luminosity function, Supermassive black holes, Active galactic nuclei, Quasars
First M87 Event Horizon Telescope Results. VII. Polarization of the Ring. In 2017 April, the Event Horizon Telescope (EHT) observed the near-horizon region around the supermassive black hole at the core of the M87 galaxy. These 1.3 mm wavelength observations revealed a compact asymmetric ring-like source morphology. This structure originates from synchrotron emission produced by relativistic plasma located in the immediate vicinity of the black hole. Here we present the corresponding linear-polarimetric EHT images of the center of M87. We find that only a part of the ring is significantly polarized. The resolved fractional linear polarization has a maximum located in the southwest part of the ring, where it rises to the level of ∼15%. The polarization position angles are arranged in a nearly azimuthal pattern. We perform quantitative measurements of relevant polarimetric properties of the compact emission and find evidence for the temporal evolution of the polarized source structure over one week of EHT observations. The details of the polarimetric data reduction and calibration methodology are provided. We carry out the data analysis using multiple independent imaging and modeling techniques, each of which is validated against a suite of synthetic data sets. The gross polarimetric structure and its apparent evolution with time are insensitive to the method used to reconstruct the image. These polarimetric images carry information about the structure of the magnetic fields responsible for the synchrotron emission. Their physical interpretation is discussed in an accompanying publication.

Keywords: Supermassive black holes, Astronomy data modeling, Very long baseline interferometry, Galaxy accretion disks, Low-luminosity active galactic nuclei, Active galactic nuclei, Radio interferometry, Polarimetry
First M87 Event Horizon Telescope Results. VIII. Magnetic Field Structure near The Event Horizon. Event Horizon Telescope (EHT) observations at 230 GHz have now imaged polarized emission around the supermassive black hole in M87 on event-horizon scales. This polarized synchrotron radiation probes the structure of magnetic fields and the plasma properties near the black hole. Here we compare the resolved polarization structure observed by the EHT, along with simultaneous unresolved observations with the Atacama Large Millimeter/submillimeter Array, to expectations from theoretical models. The low fractional linear polarization in the resolved image suggests that the polarization is scrambled on scales smaller than the EHT beam, which we attribute to Faraday rotation internal to the emission region. We estimate the average density ne ∼ 104-7 cm-3, magnetic field strength B ∼ 1-30 G, and electron temperature Te ∼ (1-12) × 1010 K of the radiating plasma in a simple one-zone emission model. We show that the net azimuthal linear polarization pattern may result from organized, poloidal magnetic fields in the emission region. In a quantitative comparison with a large library of simulated polarimetric images from general relativistic magnetohydrodynamic (GRMHD) simulations, we identify a subset of physical models that can explain critical features of the polarimetric EHT observations while producing a relativistic jet of sufficient power. The consistent GRMHD models are all of magnetically arrested accretion disks, where near-horizon magnetic fields are dynamically important. We use the models to infer a mass accretion rate onto the black hole in M87 of (3-20) × 10-4 M⊙ yr-1.

Keywords: Accretion, Magnetohydrodynamics, Jets, Black holes, Radio jets, Kerr black holes, Relativistic jets, Plasma astrophysics, Polarimetry, Radiative transfer, Event horizons, Magnetic fields
Polarimetric Properties of Event Horizon Telescope Targets from ALMA. We present the results from a full polarization study carried out with the Atacama Large Millimeter/submillimeter Array (ALMA) during the first Very Long Baseline Interferometry (VLBI) campaign, which was conducted in 2017 April in the λ3 mm and λ1.3 mm bands, in concert with the Global mm-VLBI Array (GMVA) and the Event Horizon Telescope (EHT), respectively. We determine the polarization and Faraday properties of all VLBI targets, including Sgr A*, M87, and a dozen radio-loud active galactic nuclei (AGNs), in the two bands at several epochs in a time window of 10 days. We detect high linear polarization fractions (2%-15%) and large rotation measures (RM &gt; 103.3-105.5 rad m-2), confirming the trends of previous AGN studies at millimeter wavelengths. We find that blazars are more strongly polarized than other AGNs in the sample, while exhibiting (on average) order-of-magnitude lower RM values, consistent with the AGN viewing angle unification scheme. For Sgr A* we report a mean RM of (-4.2 ± 0.3) × 105 rad m-2 at 1.3 mm, consistent with measurements over the past decade and, for the first time, an RM of (-2.1 ± 0.1) × 105 rad m-2 at 3 mm, suggesting that about half of the Faraday rotation at 1.3 mm may occur between the 3 mm photosphere and the 1.3 mm source. We also report the first unambiguous measurement of RM toward the M87 nucleus at millimeter wavelengths, which undergoes significant changes in magnitude and sign reversals on a one year timescale, spanning the range from -1.2 to 0.3 × 105 rad m-2 at 3 mm and -4.1 to 1.5 × 105 rad m-2 at 1.3 mm. Given this time variability, we argue that, unlike the case of Sgr A*, the RM in M87 does not provide an accurate estimate of the mass accretion rate onto the black hole. We put forward a two-component model, comprised of a variable compact region and a static extended region, that can simultaneously explain the polarimetric properties observed by both the EHT (on horizon scales) and ALMA (which observes the combined emission from both components). These measurements provide critical constraints for the calibration, analysis, and interpretation of simultaneously obtained VLBI data with the EHT and GMVA.

Keywords: Supermassive black holes, Galactic center, Radio jets, Quasars, Blazars, Relativistic jets, Polarimetry, Long baseline interferometry, Radio galaxies, Active galactic nuclei, Magnetic fields, Interferometry
Small-scale Dynamo in Supernova-driven Interstellar Turbulence. Magnetic fields grow quickly even at early cosmological times, suggesting the action of a small-scale dynamo (SSD) in the interstellar medium of galaxies. Many studies have focused on idealized turbulent driving of the SSD. Here we simulate more realistic supernova-driven turbulence to determine whether it can drive an SSD. Magnetic field growth occurring in our models appears inconsistent with simple tangling of magnetic fields, but consistent with SSD action, reproducing and confirming models by Balsara et al. that did not include physical resistivity η. We vary η, as well as the numerical resolution and supernova rate, $\dot{\sigma }$ &lt;!-- --&gt; , to delineate the regime in which an SSD occurs. For a given $\dot{\sigma }$ &lt;!-- --&gt; we find convergence for SSD growth rate with resolution of a parsec. For $\dot{\sigma }\simeq {\dot{\sigma }}_{\mathrm{sn}}$ &lt;!-- --&gt; , with ${\dot{\sigma }}_{\mathrm{sn}}$ &lt;!-- --&gt; the solar neighborhood rate, the critical resistivity below which an SSD occurs is $0.005\gt {\eta }_{\mathrm{crit}}\gt 0.001\,\mathrm{kpc}\,\mathrm{km}\,{{\rm{s}}}^{-1}$ &lt;!-- --&gt; , and this increases with the supernova rate. Across the modeled range of 0.5-4 pc resolution we find that for $\eta \lt {\eta }_{\mathrm{crit}}$ &lt;!-- --&gt; , the SSD saturates at about 5% of kinetic energy equipartition, independent of growth rate. In the range $0.2\,{\dot{\sigma }}_{\mathrm{sn}}\leqslant \dot{\sigma }\leqslant 8\,{\dot{\sigma }}_{\mathrm{sn}}$ &lt;!-- --&gt; growth rate increases with $\dot{\sigma }$ &lt;!-- --&gt; . SSDs in the supernova-driven interstellar medium commonly exhibit erratic growth.

Keywords: Magnetohydrodynamics, Interstellar magnetic fields, Supernova remnants, Interstellar medium, Astrophysical fluid dynamics, Supernova dynamics, Magnetohydrodynamical simulations
Mars' Formation Can Constrain the Primordial Orbits of the Gas Giants. Recent high-precision meteoritic data infers that Mars finished its accretion rapidly within 10 Myr of the beginning of the Solar System and had an accretion zone that did not entirely overlap with the Earth's. Here we present a detailed study of the accretion zone of planetary embryos from high-resolution simulations of planetesimals in a disk. We found that all simulations with Jupiter and Saturn on their current eccentric orbits (EJS) result in a similar accretion zone between fast-forming Mars and Earth-region embryos. Assuming more circular orbits for Jupiter and Saturn (CJS), on the other hand, has a significantly higher chance of forming Mars with an accretion zone not entirely dominated by Earth and Venus-region embryos; however, CJS in general forms Mars slower than in EJS. By further quantifying the degree of overlap between accretion zones of embryos in different regions with the average overlap coefficient (OVL), we found that the OVL of CJS shows a better match with the OVL from a chondritic isotopic mixing model of Earth and Mars, which indicates that the giant planets are likely to have resided on more circular orbits during gas disk dissipation than they do today, matching their suggested pre-instability orbits. More samples, including those from Mercury and Venus, could potentially confirm this hypothesis.

Keywords: Cosmochemistry, Mars, Meteorites, Cosmochronology, N-body simulations, Planet formation
Tidal Effects on the Radial Velocities of V723 Mon: Additional Evidence for a Dark 3 M<SUB>⊙</SUB> Companion. Jayasinghe et al. identified a dark ≈3 M⊙ companion on a nearly edge-on ≈60 day orbit around the red giant star V723 Monoceros as a black hole candidate in the mass gap. This scenario was shown to explain most of the data presented by Jayasinghe et al., except for periodic radial velocity (RV) residuals from the circular Keplerian model. Here we show that the RV residuals are explained by orbital phase-dependent distortion of the absorption line profile associated with changing visible fractions of the approaching and receding sides of the red giant star, whose surface is tidally deformed by and rotating synchronously with the dark companion. Our RV model constrains the companion mass M• = 2.95 ± 0.17 M⊙ and orbital inclination $i={82.9}_{-3.3}^{+7.0}\,\deg $ &lt;!-- --&gt; (medians and 68.3% highest density intervals of the marginal posteriors) adopting the radius of the red giant 24.0 ± 0.9 R⊙ as constrained from its SED and distance. The analysis provides independent support for the companion mass from ellipsoidal variations and the limits on the companion's luminosity from the absence of eclipses, both derived by Jayasinghe et al. We also show that a common scheme to evaluate the tidal RV signal as the flux-weighted mean of the surface velocity field can significantly underestimate its amplitude for RVs measured with a cross-correlation technique, and present a modified prescription that directly models the distorted line profile and its effects on the measured RVs. The formulation will be useful for estimating the component masses and inclinations in other similar binaries.

Keywords: Radial velocity, Tidal distortion, Stellar mass black holes, Red giant stars
A Nearby Repeating Fast Radio Burst in the Direction of M81. We report on the discovery of FRB 20200120E, a repeating fast radio burst (FRB) with a low dispersion measure (DM) detected by the Canadian Hydrogen Intensity Mapping Experiment FRB project. The source DM of 87.82 pc cm-3 is the lowest recorded from an FRB to date, yet it is significantly higher than the maximum expected from the Milky Way interstellar medium in this direction (∼50 pc cm-3). We have detected three bursts and one candidate burst from the source over the period 2020 January-November. The baseband voltage data for the event on 2020 January 20 enabled a sky localization of the source to within ≃14 arcmin2 (90% confidence). The FRB localization is close to M81, a spiral galaxy at a distance of 3.6 Mpc. The FRB appears on the outskirts of M81 (projected offset ∼20 kpc) but well inside its extended H I and thick disks. We empirically estimate the probability of a chance coincidence with M81 to be &lt;10-2. However, we cannot reject a Milky Way halo origin for the FRB. Within the FRB localization region, we find several interesting cataloged M81 sources and a radio point source detected in the Very Large Array Sky Survey. We search for prompt X-ray counterparts in Swift Burst Alert Telescope and Fermi/GBM data, and, for two of the FRB 20200120E bursts, we rule out coincident SGR 1806-20-like X-ray bursts. Due to the proximity of FRB 20200120E, future follow-up for prompt multiwavelength counterparts and subarcsecond localization could be constraining of proposed FRB models.

Keywords: Radio pulsars, Radio bursts, Transient sources, Radio transient sources
When the Peas Jump around the Pod: How Stellar Clustering Affects the Observed Correlations between Planet Properties in Multiplanet Systems. Recent studies have shown that the radii and masses of adjacent planets within a planetary system are correlated. It is unknown how this "peas-in-a-pod" phenomenon originates, whether it is in place at birth or requires evolution, and whether it (initially) applies only to neighboring planets or to all planets within a system. Here we address these questions by making use of the recent discovery that planetary system architectures strongly depend on ambient stellar clustering. Based on Gaia's second data release, we divide the sample of planetary systems hosting multiple planets into those residing in stellar position-velocity phase space overdensities and the field, representing samples with elevated and low degrees of external perturbation, respectively. We demonstrate that the peas-in-a-pod phenomenon manifests itself in both samples, suggesting that the uniformity of planetary properties within a system is not restricted to direct neighbors and likely already exists at birth. The radius uniformity is significantly elevated in overdensities, suggesting that it can be enhanced by evolutionary effects that either have a similar impact on the entire planetary system or favor the retention of similar planets. The mass uniformity may exhibit a similar, but weaker dependence. Finally, we find ordering in both samples, with the planet radius and mass increasing outwards. Despite its prevalence, the ordering is somewhat weaker in overdensities, suggesting that it may be disrupted by external perturbations arising from stellar clustering. We conclude that a comprehensive understanding of the peas-in-a-pod phenomenon requires linking planet formation and evolution to the large-scale stellar and galactic environment.

Keywords: Solar-planetary interactions, Exoplanet systems, Stellar dynamics, Star formation, Exoplanet formation, Planet formation
Injection of Inner Oort Cloud Objects into the Distant Kuiper Belt by Planet Nine. The outer solar system exhibits an anomalous pattern of orbital clustering, characterized by an approximate alignment of the apsidal lines and angular momentum vectors of distant, long-term stable Kuiper Belt objects. One explanation for this dynamical confinement is the existence of a yet-undetected planetary-mass object, "Planet Nine (P9)." Previous work has shown that trans-Neptunian objects, that originate within the scattered disk population of the Kuiper Belt, can be corralled into orbital alignment by Planet Nine's gravity over ∼Gyr timescales, and characteristic P9 parameters have been derived by matching the properties of a synthetic Kuiper Belt generated within numerical simulations to the available observational data. In this work, we show that an additional dynamical process is in play within the framework of the Planet Nine hypothesis, and demonstrate that P9-induced dynamical evolution facilitates orbital variations within the otherwise dynamically frozen inner Oort cloud. As a result of this evolution, inner Oort cloud bodies can acquire orbits characteristic of the distant scattered disk, implying that if Planet Nine exists, the observed census of long-period trans-Neptunian objects is comprised of a mixture of Oort cloud and Kuiper Belt objects. Our simulations further show that although inward-injected inner Oort cloud objects exhibit P9-driven orbital confinement, the degree of clustering is weaker than that of objects originating within the Kuiper Belt. Cumulatively, our results suggest that a more eccentric Planet Nine is likely necessary to explain the data than previously thought.

Keywords: Planetary dynamics, Oort cloud objects, Trans-Neptunian objects
First Demonstration of Early Warning Gravitational-wave Alerts. Gravitational-wave observations became commonplace in Advanced LIGO-Virgo's recently concluded third observing run. 56 nonretracted candidates were identified and publicly announced in near real time. Gravitational waves from binary neutron star mergers, however, remain of special interest since they can be precursors to high-energy astrophysical phenomena like γ-ray bursts and kilonovae. While late-time electromagnetic emissions provide important information about the astrophysical processes within, the prompt emission along with gravitational waves uniquely reveals the extreme matter and gravity during—and in the seconds following—merger. Rapid communication of source location and properties from the gravitational-wave data is crucial to facilitate multimessenger follow-up of such sources. This is especially enabled if the partner facilities are forewarned via an early warning (pre-merger) alert. Here we describe the commissioning and performance of such a low-latency infrastructure within LIGO-Virgo. We present results from an end-to-end mock data challenge that detects binary neutron star mergers and alerts partner facilities before merger. We set expectations for these alerts in future observing runs.

Keywords: Gravitational wave astronomy, Neutron stars, Gravitational waves, High energy astrophysics
The Role of Strong Gravity and the Nuclear Equation of State on Neutron-star Common-envelope Accretion. Common-envelope evolution is important in the formation of neutron star binaries within the isolated binary formation channel. As a neutron star inspirals within the envelope of a primary massive star, it accretes and spins up. Because neutron stars are in the strong-gravity regime, they have a substantial relativistic mass deficit, i.e., their gravitational mass is less than their baryonic mass. This effect causes some fraction of the accreted baryonic mass to convert into neutron star binding energy. The relativistic mass deficit also depends on the nuclear equation of state, since more compact neutron stars will have larger binding energies. We model the mass growth and spin-up of neutron stars inspiraling within common-envelope environments and quantify how different initial binary conditions and hadronic equations of state affect the post-common-envelope neutron star's mass and spin. From these models, we find that neutron star mass growth is suppressed by ≈15%-30%. We also find that for a given amount of accreted baryonic mass, more compact neutron stars will spin-up faster while gaining less gravitational mass, and vice versa. This work demonstrates that a neutron star's strong gravity and nuclear microphysics plays a role in neutron-star-common-envelope evolution, in addition to the macroscopic astrophysics of the envelope. Strong gravity and the nuclear equation of state may thus affect both the population properties of neutron star binaries and the cosmic double neutron star merger rate.

Keywords: Neutron stars, Accretion, Compact objects, Common envelope evolution, Nuclear physics