Sazuna/UAT_keywords huggingface dataset:
Targeted Modeling of GW150914's Binary Black Hole Source with Dart_board. We present a new method to extract statistical constraints on the progenitor properties and formation channels of individual gravitational-wave sources. Although many different models have been proposed to explain the binary black holes detected by the LIGO Scientific and Virgo Collaboration (LVC), formation through isolated binary evolution remains the best-explored channel. Under the assumption of formation through binary evolution, we use the statistical wrapper Dart_board coupled with the rapid binary evolution code COSMIC to model the progenitor of GW150914, the first gravitational-wave signal detected by the LVC. Our Bayesian method combines the likelihood generated from the gravitational-wave signal with a prior describing the population of stellar binaries and the universes star formation and metallicity evolution. We find that the dominant evolutionary channel for GW150914 did not involve a common-envelope phase, but instead the system most probably (7090) formed through stable mass transfer. This result is robust against variations of various model parameters, and it is reversed only when dynamical instability in binaries becomes more likely when a strict condition favoring common envelopes is adopted. Our analysis additionally provides a quantitative description of the progenitors relevant to each channel.

Keywords: LIGO, Binary stars, Interacting binary stars, Gravitational wave sources
Modeling Interactions of Narrowband Large Amplitude Whistler-mode Waves with Electrons in the Solar Wind inside 0.3 au and at 1 au Using a Particle Tracing Code. The discovery of large amplitude narrowband whistler-mode waves at frequencies oftenths of the electron cyclotron frequency in large numbers both inside 0.3 au and at 1 au provides an answer to longstanding questions about scattering and energization of solar wind electrons. The waves can have rapid nonlinear interactions with electrons over a broad energy range. Counter propagation between electrons and waves is not required for resonance with the obliquely propagating waves in contrast to the case for parallel propagation. Using a full 3D particle tracing code, we have examined interactions of electrons with energies from 0 eV to 2 keV with whistler-mode waves with amplitudes of 20 mV m1 andpropagation angles from 0 to 180 to the background magnetic field. Interactions with wave packets and single waves are both modeled based on observations at 0.3 au and 1 au. A test particle simulation approach allows us to examine the particle motion in detail, which reveals kinetic effects of resonant interactions. The simulations demonstrate the key role played by these waves in rapid scattering and energization of electrons. Strong scattering and energization for some initial energy and pitch angle ranges occurs for both counter-propagating and obliquely propagating waves. Strong scattering of strahl electrons counteracts the pitch angle narrowing due to conservation of the first adiabatic invariant as electrons propagate from the Sun into regions of smaller magnetic field. Scattering also produces the hotter isotropic halo. The concomitant limiting of the electron heat flux is also relevant in other astrophysical settings.

Keywords: Solar physics, Plasma astrophysics, Plasma physics
Do LIGO/Virgo Black Hole Mergers Produce AGN Flares? The Case of GW190521 and Prospects for Reaching a Confident Association. The recent report of an association of the gravitational-wave (GW) binary black hole (BBH) merger GW190521 with a flare in the active galactic nuclei (AGNs) J124942.3 344929 has generated tremendous excitement. However, GW190521 has one of the largest localization volumes among all of the GW events detected so far. The 90 localization volume likely contains 7400 unobscured AGNs brighter than g 20.5 AB mag, and it results in a 70 probability of chance coincidence for an AGN flare consistent with the GW event. We present a Bayesian formalism to estimate the confidence of an AGN association by analyzing a population of BBH events with dedicated follow-up observations. Depending on the fraction of BBHs arising from AGNs, counterpart searches of ${ \mathcal O }(1)-{ \mathcal O }(100)$ GW events are needed to establish a confident association, and more than an order of magnitude more for searches without follow-up (i.e., using only the locations of AGN and GW events). Follow-up campaigns of the top 5 (based on volume localization and binary mass) of BBH events with total rest-frame mass 50 M are expected to establish a confident association during the next LIGO/Virgo/KAGRA observing run (O4), as long as the true value of the fraction of BBHs giving rise to AGN flares is &gt;0.1. Our formalism allows us to jointly infer cosmological parameters from a sample of BBH events that include chance coincidence flares. Until the confidence of AGN associations is established, the probability of chance coincidence must be taken into account to avoid biasing astrophysical and cosmological constraints.

Keywords: Cosmology, High energy astrophysics, Transient sources, Gravitational wave sources, Gravitational wave astronomy, Active galactic nuclei, Gravitational waves, Time domain astronomy
Homologous Microflares with Mass Ejection and Plasma Heating on the Quiet Sun. Study of microflares on the quiet Sun is extremely important in learning the physics of both solar flare and atmospheric heating. Here, for the first time, we report the detailed observations of two homologous microflares from Atmospheric Imager Assembly (AIA) images and Heliospheric Magnetic Imager magnetograms in a very quiet region. The two microflares are observed clearly in the extreme ultraviolet and faintly in the ultraviolet in AIA images. They have an area of 59 Mm2 and 46 Mm2, and a duration of 25 minutes and 22 minutes. The magnetic cancellation continuously takes place during the microflares, and the magnetic flux decrease is apparent, with a value of 4 1018 Mx. The obvious mass ejections are observed during the microflares, and dimming occurs during and after the microflares. The velocity of mass ejection is up to 160 km s1. For the two microflares, the time of peak intensity in 30.4 nm precedes that of the coronal peak emission, up to 2.43.3 minutes. Their thermal energy is estimated to be 1.3 1027 erg and 2.5 1026 erg, respectively, which heats the corona up to 5.8 MK and 2.8 MK. There are many similarities of microflares on the quiet Sun to major flares in the active regions.

Keywords: Solar activity, Solar ultraviolet emission, Solar magnetic fields
Proton Energization by Phase Steepening of Parallel-propagating Alfvénic Fluctuations. Proton energization at magnetic discontinuities generated by phase-steepened fronts of parallel-propagating, large-amplitude Alfvénic fluctuation is studied using hybrid simulations. We find that dispersive effects lead to the collapse of the wave via phase steepening and the subsequent generation of compressible fluctuations that mediate an efficient local energy transfer from the wave to the protons. Proton scattering at the steepened edges causes nonadiabatic proton perpendicular heating. Furthermore, the parallel electric field at the propagating fronts mediates the acceleration of protons along the mean field. A steady-state is achieved where the proton distribution function displays a field-aligned beam at the Alfvén speed, and compressible fluctuations are largely damped. We discuss the implications of our results in the context of Alfvénic solar wind.

Keywords: Interplanetary turbulence, Interplanetary discontinuities, Interplanetary particle acceleration, Alfven waves
The Challenge to MOND from Ultra-faint Dwarf Galaxies. Modified Newtonian dynamics (MOND) at low acceleration has been astonishingly powerful at explaining the rotation curve of galaxies and the relation between the baryonic content of the galaxies and their observed circular velocity, known as the baryonic TullyFisher relationship. It is known that MOND fails at explaining the observed velocity dispersion of the ultra-faint dwarf galaxies (UFDs) with the justification that UFDs are more prone to tidal disruption in MOND compared to cold dark matter model. We show that (i) the ratio of tidal to internal acceleration in UFDs is extremely low, (ii) there is no correlation between the deviation of UFDs from MONDs prediction as a function of tidal susceptibility, and (iii) recent constraints from Gaia proper motion analysis on the orbital parameters of the UFDs exacerbate the challenge to MOND. In particular, Gaia data indicate that Ursa Major I is experiencing a recent infall into the Milky Ways halo, and its inconsistency with MOND at the 7 level cannot be attributed to being an early infall satellite. Moreover, the new data from Gaia DR2 show Willman I to have the least eccentric orbit of all UFDs, and its deviation from MOND at the 4 level cannot be attributed to a highly eccentric orbit as previously suggested. Finally, given that Tuc III is the only UFD observed to show tidal features, Reticulum II and Segue I are two other UFDs that potentially challenge MOND as they have comparable Galactocentric distances to Tuc III while showing no tidal features.

Keywords: Cold dark matter, Modified Newtonian dynamics, Dwarf galaxies
Thermal Wave Instability as an Origin of Gap and Ring Structures in Protoplanetary Disks. Recent millimeter and infrared observations have shown that gap- and ring-like structures are common in both dust thermal emission and scattered light of protoplanetary disks. We investigate the impact of the so-called thermal wave instability (TWI) on the millimeter and infrared scattered light images of disks. We perform 11D simulations of the TWI and confirm that the TWI operates when the disk is optically thick enough for stellar light, i.e., small-grain-to-gas mass ratio of 0.0001. The midplane temperature varies as the waves propagate, and hence gap and ring structures can be seen in both millimeter and infrared emission. The millimeter substructures can be observed even if the disk is fully optically thick since it is induced by the temperature variation, while density-induced substructures would disappear in the optically thick regime. The fractional separation between TWI-induced ring and gap is r/r 0.20.4 at 1050 au, which is comparable to those found by the Atacama Large Millimeter/submillimeter Array. Due to the temperature variation, snow lines of volatile species move radially and multiple snow lines are observed even for a single species. The wave propagation velocity is as fast as 0.6 au yr1, which can be potentially detected with a multiepoch observation with a time separation of a few years.

Keywords: Protoplanetary disks, Planet formation
The Double-bubble Coronal Mass Ejection of the 2020 December 14 Total Solar Eclipse. Total solar eclipses (TSEs) continue to provide an invaluable platform for exploring the magnetic topology of the solar corona and for studying dynamic events such as coronal mass ejections (CMEs)with a higher spatial resolution over a larger spatially continuous extent than is possible to achieve with any other method at present. In this Letter, we present observations of the full extent of a double-bubble CME structure from the solar surface out to over 5 solar radii, as captured during the 2020 December 14 TSE. Its evolution through the corona was recorded from two observing sites separated by 13 minutes in their times of totality. The eclipse observations are complemented by a plethora of space-based observations including: Extreme Ultraviolet observations of the solar disk and low corona from SDO/AIA and STEREO-A/EUVI, white-light coronagraph observations from SOHO/LASCO-C2, radio from STEREO-A/WAVES and WIND/WAVES, and X-ray from GOES-16. We also characterize the magnetic field with a potential field source surface model. This CME event itself is of particular interest, as it demonstrates interactions between a prominence channel and an active region that led to the double-bubble structure. Despite the plethora of space-based observations, only the eclipse data are able to provide the proper context to connect these observations and yield a detailed study of this unique CME.

Keywords: Solar prominences, Solar eclipses, Solar active regions, Solar coronal mass ejections, Solar corona, Solar coronal streamers
Cosmological Evolution of the Formation Rate of Short Gamma-Ray Bursts with and without Extended Emission. Originating from neutron starneutron star or neutron starblack hole mergers, short gamma-ray bursts (SGRBs) are the first electromagnetic emitters associated with gravitational waves (GWs). This association makes the determination of SGRB formation rate (FR) a critical issue. We determine the true SGRB FR and its relation to the cosmic star formation rate (SFR). This can help in determining the expected GW rate involving small mass mergers. We present nonparametric methods for the determination of the evolutions of the luminosity function (LF) and the FR using SGRBs observed by Swift, without any assumptions. These are powerful tools for small samples, such as our sample of 68 SGRBs. We combine SGRBs with and without extended emission (SEE), assuming that both descend from the same progenitor. To overcome the incompleteness introduced by redshift measurements we use the KolmogorovSmirnov (KS) test to find flux thresholds yielding a sample of sources with a redshift drawn from the parent sample including all sources. Using two subsamples of SGRBs with flux limits of 4.57 107 and 2.15 107 erg cm2 s1 with respective KS p (1, 0.9), we find a 3 evidence for luminosity evolution (LE), a broken power-law LF with significant steepening at L 1050 erg s1, and an FR evolution that decreases monotonically with redshift (independent of LE and the thresholds). Thus, SGRBs may have been more luminous in the past with an FR delayed relative to the SFR as expected in the merger scenario.

Keywords: Gamma-ray bursts
PGC 38025: A Star-forming Lenticular Galaxy with an Off-nuclear Star-forming Core. Lenticular galaxies (S0s) were considered mainly as passive evolved spirals due to environmental effects for a long time; however, most S0s in the field cannot fit into this common scenario. In this work, we study one special case, Sloan Digital Sky Survey J120237.07+642235.3 (PGC 38025), a star-forming field S0 galaxy with an off-nuclear blue core. We present optical integral field spectroscopic observation with the 3.5 meter telescope at Calar Alto Observatory, and high-resolution millimeter observation with the NOrthern Extended Millimeter Array. We estimated the star formation rate (SFR = 0.446 M⊙ yr-1) and gaseous metallicity (12 + log(O/H) = 8.42) for PGC 38025, which follows the star formation main sequence and stellar mass-metallicity relation. We found that the ionized gas and cold molecular gas in PGC 38025 show the same spatial distribution and kinematics, while rotating misaligned with stellar component. The off-nuclear blue core is locating at the same redshift as PGC 38025 and its optical spectrum suggest it is H II region. We suggest that the star formation in PGC 38025 is triggered by a gas-rich minor merger, and the off-nuclear blue core might be a local star formation happened during the accretion/merger process.

Keywords: Lenticular galaxies, Early-type galaxies, Star formation, Galaxy kinematics, Galaxies
The Orbit and Nature of the Semidetached Stellar Companion of the Sgr A* Supermassive Black Hole. In three previous papers I showed that the series of the midpoints of the times of all the X-ray flares of Sgr A* that have been detected so far harbor a statistical trend termed pacemaker regularity. This means that X-ray flares are detected more frequently around time points that are a subset of a periodic grid on the time axis of period PX = 0.1032 day = 149 minutes. The series of the times of detection of the peaks of near-IR (NIR) flares of the object are also regulated by a pacemaker, with a period of PIR = 0.028 day = 41 minutes. Here, I show that the series of the midpoints of the times of recorded NIR flares are also regulated by a pacemaker of the period PIRM = 0.039 day = 56 minutes. The two pacemakers found in the previous papers were interpreted as signals of a star that revolves around the black hole of Sgr A* in orbit with a mean radius of ~3.2 Schwarzschild radii of the black hole, here corrected to ~3.13. The finding of the period of the third pacemaker is consistent with the suggested revolving star model. Here, I present the specific orbit of the star as well as a plausible description of its sidereal rotation. The model also implies that the star has an unusual internal structure. I show that the discovery of the GRAVITY Collaboration of the motion of hotspots at distances from the black hole that are of the order of very few Schwarzschild radii of it may well be understood within the context of the revolving star model.

Keywords: Infrared sources, Galactic center, Black holes, X-ray bursts
Foreshock as a Source Region of Electron-scale Magnetic Holes in the Solar Wind at 1 au. Electron-scale magnetic holes (ESMHs) can dissipate energy and transport electrons in astrophysical plasmas. They are often observed in the solar wind at 1 au, but whether they are locally generated remains unclear. Here we investigate the ESMHs in the solar wind at 1 au based on observations of the Magnetospheric Multiscale (MMS) and Acceleration, Reconnection, Turbulence and Electrodynamics of the Moon's Interaction with the Sun (ARTEMIS) P1 spacecraft. There are 47 and 18 ESMH events observed by MMS1 and ARTEMIS P1, respectively, where an isolated ESMH or a train of ESMHs is regarded as an ESMH event. Our findings are as follows: (1) the occurrence rate of the ESMH events observed by MMS1 is much larger than that by ARTEMIS P1, which is located in the upstream solar wind; and (2) the proportion of the train of ESMHs in the ESMH events observed by each spacecraft is much higher in the ion foreshock than that in the undisturbed solar wind. These observations suggest that the terrestrial foreshock is an important source region of the ESMHs at 1 au, while some ESMHs come from the upstream undisturbed solar wind. The generation of these ESMHs can be explained by the electron vortex magnetic hole. Finding out the origin of the electron vortex may help to shed light on the whole chain of their generation and evolution in the foreshock.

Keywords: Solar wind
What Makes Quadruply Lensed Quasars Quadruple?. Among known strongly lensed quasar systems, ~25% have gravitational potentials sufficiently flat (and sources sufficiently well aligned) to produce four images rather than two. The projected flattening of the lensing galaxy and tides from neighboring galaxies both contribute to the potential's quadrupole. Witt's hyperbola and Wynne's ellipse permit determination of the overall quadrupole from the positions of the quasar images. The position of the lensing galaxy resolves the distinct contributions of intrinsic ellipticity and tidal shear to that quadrupole. Among 31 quadruply lensed quasars systems with statistically significant decompositions, 15 are either reliably (2σ) or provisionally (1σ) shear-dominated and 11 are either reliably or provisionally ellipticity-dominated. For the remaining eight, the two effects make roughly equal contributions to the combined cross section (newly derived here) for quadruple lensing. This observational result is strongly at variance with the ellipticity-dominated forecast of Oguri &amp; Marshall.

Keywords: Strong gravitational lensing
The ACTIONFINDER: An Unsupervised Deep Learning Algorithm for Calculating Actions and the Acceleration Field from a Set of Orbit Segments. We introduce the ACTIONFINDER, a deep learning algorithm designed to transform a sample of phase-space measurements along orbits in a static potential into action and angle coordinates. The algorithm finds the mapping from positions and velocities to actions and angles in an unsupervised way, by using the fact that points along the same orbit have identical actions. Here we present the workings of the method and test it on simple axisymmetric models, comparing the derived actions to those generated with the Torus Mapping technique. We show that it recovers the torus actions for halo-type orbits in a realistic model of the Milky Way to ~0.6% accuracy with as few as 1024 input phase-space measurements. These actions are much better conserved along orbits than those estimated with the Stäckel fudge. In our case, the reciprocal mapping from actions and angles to positions and velocities can also be learned. One of the advantages of the ACTIONFINDER is that it does not require the underlying potential to be known in advance-indeed it is designed to return the acceleration field. We expect the algorithm to be useful for analyzing the properties of dynamical systems in numerical simulations. However, our ultimate goal with this effort will be to apply it to real stellar streams to recover the Galactic acceleration field in a way that is relatively agnostic about the underlying dark matter properties or the behavior of gravity.

Keywords: Celestial mechanics, Milky Way Galaxy, Neural networks
Multifluid MHD Studies of the Ionospheric Magnetic Flux Ropes at Mars. We use a multifluid MHD model to study the formation of the small-scale magnetic flux rope (MFR) in the ionosphere of Mars. It is found that a straight flux tube can turn into a twisted MFR during its sinking into the lower ionosphere, caused by the differential compression at different parts of the tube. Further studies show that the MFR is not a force-free structure, in which there is always a pressure gradient force to balance the magnetic force. Moreover, we find that the ionospheric ions inside the MFR can be squeezed out from the two ends of the MFR, with an outflow flux of about 3.5 × 107 cm-2 s-1, which can play an important role for the ion escape from Mars. In addition, we find that both the sinking speed and the ratio of the ion gyroradius to the tube radius can affect the characteristics of MFR. An MFR can be more quickly formed for a larger sinking speed, but it can be also more quickly filled by the ambient ions. Oppositely, the MFR is more difficult to be filled when the ratio of the ion gyroradius to the tube radius is smaller. Once the MFR is filled, the compression is prevented by an outward pressure gradient force, and both the field strength and the rope helicity begin to decrease. Our results can explain the different altitude dependences of MFRs observed at Mars and Venus.

Keywords: Space plasmas, Planetary magnetospheres