adsabs/SciX_UAT_keywords huggingface dataset:
A New Database of Giant Impacts over a Wide Range of Masses and with Material Strength: A First Analysis of Outcomes

In the late stage of terrestrial planet formation, planets are predicted to undergo pairwise collisions known as giant impacts. Here, we present a high-resolution database of giant impacts for differentiated colliding bodies of iron–silicate composition, with target masses ranging from 1 × 10‑4 M ⊕ up to super-Earths (5 M ⊕). We vary the impactor-to-target mass ratio, core–mantle (iron–silicate) fraction, impact velocity, and impact angle. Strength in the form of friction is included in all simulations. We find that, due to strength, the collisions with bodies smaller than about 2 ×10‑3 M ⊕ can result in irregular shapes, compound-core structures, and captured binaries. We observe that the characteristic escaping velocity of smaller remnants (debris) is approximately half of the impact velocity, significantly faster than currently assumed in N-body simulations of planet formation. Incorporating these results in N-body planet formation studies would provide more realistic debris–debris and debris–planet interactions.

Keywords: planet formation; solar system terrestrial planets; extrasolar rocky planets
The Effect of Nanoflare Flows on EUV Spectral Lines

The nanoflare model of coronal heating is one of the most successful scenarios to explain, within a single framework, the diverse set of coronal observations available with the present instrument resolutions. The model is based on the idea that the coronal structure is formed by elementary magnetic strands which are tangled and twisted by the displacement of their photospheric footpoints by convective motions. These displacements inject magnetic stress between neighboring strands that promotes current sheet formation, reconnection, plasma heating, and possibly also particle acceleration. Among other features, the model predicts the ubiquitous presence of plasma flows at different temperatures. These flows should, in principle, produce measurable effects on observed spectral lines in the form of Doppler shifts, line asymmetries and nonthermal broadenings. In this work we use the two-dimensional cellular automaton model (2DCAM) developed in previous works, in combination with the enthalpy-based thermal evolution of loops (EBTEL) model, to analyze the effect of nanoflare heating on a set of known EUV spectral lines. We find that the complex combination of the emission from plasmas at different temperatures, densities and velocities, in simultaneously evolving unresolved strands, produces characteristic properties in the constructed synthetic lines, such as Doppler shifts and nonthermal velocities up to tens of km s-1 for the higher analyzed temperatures. Our results might prove useful to guide future modeling and observations, in particular, regarding the new generation of proposed instruments designed to diagnose plasmas in the 5-10 MK temperature range.

Keywords: solar corona; solar coronal heating; solar coronal loops; solar coronal lines
Environments of Type Ia Supernovae with Different Relative Equivalent Widths of the Si II Feature in Their Spectra

Although type Ia supernovae (SNe Ia) are very important in many astrophysical fields, such as cosmology, their explosion mechanisms and progenitor systems still remain unclear. In physics, the relative equivalent width (REW) of the Si II 635.5 nm absorption feature reflects the velocity interval of the silicon in the SN ejecta, which may then provide constraints on the explosion mechanisms of SNe Ia. In this paper, we divide the SNe Ia into broad-line (BL) and normal-line (NL) subsamples, based on the REW of the Si II 635.5 nm absorption lines around their maximum lights, and we find that the BL SNe Ia have a dimmer mean brightness than the NL ones, which is possibly a result of their different metallicities. However, based on a pixel statistics study of the environments of the two subsamples, we do not find any significant potential differences in the environments of the BL and NL SNe Ia, which implies that the explosion mechanisms of SNe Ia could be independent of their progenitor populations.

Keywords: type ia supernovae; white dwarf stars; supernova remnants
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
Observational Signatures of Coronal Heating in Magnetohydrodynamic Simulations without Radiation or a Lower Atmosphere

It is extremely difficult to simulate the details of coronal heating and also make meaningful predictions of the emitted radiation. Thus, testing realistic models with observations is a major challenge. Observational signatures of coronal heating depend crucially on radiation, thermal conduction, and the exchange of mass and energy with the transition region and chromosphere below. Many magnetohydrodynamic simulation studies do not include these effects, opting instead to devote computational resources to the magnetic aspects of the problem. We have developed a simple method of accounting approximately for the missing effects. It is applied to the simulation output ex post facto and therefore may be a valuable tool for many studies. We have used it to predict the emission from a model corona that is driven by vortical boundary motions meant to represent photospheric convection. We find that individual magnetic strands experience short-term brightenings, both scattered throughout the computational volume and in localized clusters. The former may explain the diffuse component of the observed corona, while the latter may explain bright coronal loops. Several observed properties of loops are reproduced reasonably well: width, lifetime, and quasi-circular cross section (aspect ratio not high). Our results lend support to the idea that loops are multistranded structures heated by "storms" of nanoflares.

Keywords: solar coronal heating; solar active regions; stellar coronae; solar magnetic reconnection; solar corona; magnetohydrodynamics; solar coronal loops; solar extreme ultraviolet emission
The Deepest Radio Observations of Nearby SNe Ia: Constraining Progenitor Types and Optimizing Future Surveys

We report deep radio observations of nearby Type Ia supernovae (SNe Ia) with the electronic Multi-Element Radio Linked Interferometer Network and the Australia Telescope Compact Array. No detections were made. With standard assumptions for the energy densities of relativistic electrons going into a power-law energy distribution and the magnetic field strength (ɛe = ɛB = 0.1), we arrive at upper limits on mass-loss rate for the progenitor system of SN 2013dy (SN 2016coj, SN 2018gv, SN 2018pv, SN 2019np) of $\dot{M}\lesssim 12\,(2.8,1.3,2.1,1.7)\times {10}^{-8}\,{M}_{\odot }\,{\mathrm{yr}}^{-1}({V}_{w}/100\,\mathrm{km}\,{{\rm{s}}}^{-1})$ , where Vw is the wind speed of the mass loss. To SN 2016coj, SN 2018gv, SN 2018pv, and SN 2019np we add radio data for 17 other nearby SNe Ia and model their nondetections. With the same model as described, all 21 SNe Ia have $\dot{M}\lesssim 4\times {10}^{-8}\,{M}_{\odot }\,{\mathrm{yr}}^{-1}({V}_{w}/100\,\mathrm{km}\,{{\rm{s}}}^{-1})$ . We compare those limits with the expected mass-loss rates in different single-degenerate progenitor scenarios. We also discuss how information on ɛe and ɛB can be obtained from late observations of SNe Ia and the youngest SN Ia remnant detected in radio, G1.9+0.3, as well as stripped-envelope core-collapse SNe. We highlight SN 2011dh and argue for ɛe ≈ 0.1 and ɛB ≈ 0.0033. Finally, we discuss strategies to observe at radio frequencies to maximize the chance of detection, given the time since explosion, the distance to the SN, and the telescope sensitivity.

Keywords: supernova remnants; type ia supernovae; white dwarf stars; stellar mass loss; radio continuum emission
Multi-scale Radio and X-Ray Structure of the High-redshift Quasar PMN J0909+0354

The high-redshift quasar PMN J0909+0354 (z = 3.288) is known to have a parsec-scale compact jet structure, based on global 5 GHz very long baseline interferometry (VLBI) observations performed in 1992. Its kiloparsec-scale structure was studied with the Karl G. Jansky Very Large Array (VLA) in the radio and the Chandra space telescope in X-rays. Apart from the north-northwestern jet component seen in both the VLA and Chandra images at 2"3 separation from the core, there is another X-ray feature at 6"48 in the northeastern (NE) direction. To uncover more details and possible structural changes in the inner jet, we conducted new observations at 5 GHz using the European VLBI Network in 2019. These data confirm the northward direction of the one-sided inner jet already suspected from the 1992 observations. A compact core and multiple jet components were identified that can be traced up to ~0.25 kpc projected distance toward the north, where the structure becomes more and more diffuse. A comparison with arcsecond-resolution imaging with the VLA shows that the radio jet bends by ~30° between the two scales. The direction of the parsec-scale jet as well as the faint optical counterpart found for the newly detected X-ray point source (NE) favors the nature of the latter as being a background or foreground object in the field of view. However, the extended (~160 kpc) emission around the positions of the quasar core and NE detected by the Wide-field Infrared Survey Explorer in the mid-infrared might suggest a physical interaction of the two objects.

Keywords: x-ray active galactic nuclei; radio continuum emission; jets; blazars; quasars; active galactic nuclei
The EDGE-CALIFA Survey: An Extragalactic Database for Galaxy Evolution Studies

The EDGE-CALIFA survey provides spatially resolved optical integral-field unit and CO spectroscopy for 125 galaxies selected from the Calar Alto Legacy Integral Field Area Survey (CALIFA) Data Release 3 sample. The Extragalactic Database for Galaxy Evolution (EDGE) presents the spatially resolved products of the survey as pixel tables that reduce the oversampling in the original images and facilitate comparison of pixels from different images. By joining these pixel tables to lower-dimensional tables that provide radial profiles, integrated spectra, or global properties, it is possible to investigate the dependence of local conditions on large-scale properties. The database is freely accessible and has been utilized in several publications. We illustrate the use of this database and highlight the effects of CO upper limits on the inferred slopes of the local scaling relations between the stellar mass, star formation rate (SFR), and H2 surface densities. We find that the correlation between H2 and SFR surface density is the tightest among the three relations.

Keywords: molecular gas; star formation; astronomy databases; galaxy evolution; spiral galaxies
Analytic Marginalization of Absorption Line Continua

Absorption line spectroscopy is a powerful way of measuring properties of stars and the interstellar medium. Absorption spectra are often analyzed manually, an approach that limits reproducibility and which cannot practically be applied to modern data sets consisting of thousands or even millions of spectra. Simultaneous probabilistic modeling of absorption features and continuum shape is a promising approach for automating this analysis. Existing implementations of this approach use numerical methods such as Markov Chain Monte Carlo to marginalize over the continuum parameters. When continua are parameterized as linear functions such as polynomials or splines, it is possible to reduce continuum parameter marginalization to an integral over a multivariate normal distribution, which has a known closed form. Analytic marginalization makes it possible to combine optimization for absorption line parameters with marginalization of nuisance continuum parameters. We compare the accuracy to within which absorption line parameters can be recovered using different continuum placement methods and find that marginalization with an informative prior on continuum parameters is a clear improvement over other continuum placement methods over a broad range of signal-to-noise ratios. We implement analytic marginalization over linear continuum parameters in the open-source package amlc.

Keywords: spectroscopy; astrostatistics techniques; interstellar line absorption
The Wind Temperature and Mass-loss Rate of Arcturus (K1.5 III)

In this paper we aim to constrain the wind temperature, outflow and turbulent velocities, ionization state, and mass-loss rate of the single red giant Arcturus (α Boo K1.5 III) using high spectral resolution Hubble Space Telescope Space Telescope Imaging Spectrograph profiles of Si III 1206.5 Å , O I 1304 Å and 1306 Å, C II 1334 Å and 1335 Å, and Mg II h 2802 Å. The use of the E140-H setting for α Boo allows the Si III 1206.5 Å line to be cleanly extracted from the echelle format for the first time. The ratios of the wind optical depths of lines from different species constrain the temperature at the base of the wind to T wind ~ 15,400 K. The mass-loss rate derived is 2.5 × 10-11 $\,{{M}_{\odot }\,{\rm{yr}}}^{-1}$ for Epoch 2018-2019, smaller than previous semiempirical estimates. These results can be reconciled with multiwavelength Very Large Array radio continuum fluxes for Epoch 2011-2012 by increasing the temperature to T wind ~ 18,000 K, or increasing the mass-loss rate to 4.0 × 10-11 $\,{{M}_{\odot }\,{\rm{yr}}}^{-1}$ . Interpreting the wind acceleration and turbulence in terms of a steady WKB Alfvén wave-driven wind reveals that the wave energy damping length increases with increasing radius, opposite to the trend expected for ion-neutral damping of monochromatic waves, confirming a previous result by Kuin and Ahmad derived for ζ Aur binaries. This implies that a spectrum of waves is required in this framework with wave periods in the range of hours to days, consistent with the photospheric granulation timescale. Constraints on a radial magnetic field (B) at 1.2 R * are an upper limit of B ≤ 2 G from the implied wave heating, and B ≥ 0.3 G to avoid excessive wave amplitudes.

Keywords: stellar winds; alfven waves; stellar spectral lines; hubble space telescope; stellar mass loss
Atomic Transition Probabilities of Neutral Calcium

The goals of this study are (1) to test the best theoretical transition probabilities for Ca I (a relatively light alkaline earth spectrum) from a modern ab initio calculation using configuration interaction plus many-body perturbation theory against the best modern experimental transition probabilities and (2) to produce as accurate and comprehensive a line list of Ca I transition probabilities as is currently possible based on this comparison. We report new Ca I radiative lifetime measurements from a laser-induced fluorescence experiment and new emission branching fraction measurements from a 0.5 m focal length grating spectrometer with a detector array. We combine these data for upper levels that have both a new lifetime and new branching fractions to report log(gf) values for two multiplets consisting of nine transitions. Detailed comparisons are made between theory and experiment, including the measurements reported herein and a selected set of previously published experimental transition probabilities. We find that modern theory compares favorably to experimental measurements in most instances where such data exist. A final list of 202 recommended transition probabilities is presented, which covers lines of Ca I with wavelengths ranging from 2200 to 10000 Å. These are mostly selected from theory but are augmented with high-quality experimental measurements from this work and from the literature. The recommended transition probabilities are used in a redetermination of the Ca abundance in the Sun and in the metal-poor star HD 84937. * Based on observations made with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. The data presented in this paper were obtained from the Barbara A. Mikulski Archive for Space Telescopes. Other data have been obtained from the European Southern Observatory Science Archive Facility.

Keywords: atomic data benchmarking; atomic spectroscopy; stellar abundances; solar abundances
Jupiter's Dynamical Love Number

Recent observations by the Juno spacecraft have revealed that the tidal Love number k2 of Jupiter is 4% lower than the hydrostatic value. We present a simple calculation of the dynamical Love number of Jupiter that explains the observed "anomaly." The Love number is usually dominated by the response of the (rotation-modified) f-modes of the planet. Our method also allows for efficient computation of high-order dynamical Love numbers. While the inertial-mode contributions to the Love numbers are negligible, a sufficiently strong stratification in a large region of the planet's interior would induce significant g-mode responses and influence the measured Love numbers.

Keywords: solar system gas giant planets
The Most Massive Binary Black Hole Detections and the Identification of Population Outliers

Advanced LIGO and Virgo detected 10 binary black holes (BBHs) in their first two observing runs (O1 and O2). Analysis of these events found evidence for a dearth of BBHs with component masses greater than ∼45 M⊙, as would be expected from pair-instability supernovae. Meanwhile, a standalone analysis of the merger GW170729 found its primary mass to be {m}1={51.2}-11.0+16.2 {M}⊙, which appears to be in contradiction with the existence of a limit at ∼45 M⊙. In this work, we argue that the masses of individual events can only be evaluated with reference to the full population. When GW170729 is analyzed jointly with the remaining detections, its inferred primary mass tightens considerably, to {m}1={38.9}-4.5+7.3 {M}⊙ . In the presence of noise, apparent outliers in the detected distribution are inevitable. We discuss methods of distinguishing between statistical fluctuations and true population outliers using posterior predictive tests. Applying these tests to O1 and O2, we find that the 10 detections are consistent with even the simplest power-law plus maximum-mass model considered by the LIGO-Virgo Collaboration, supporting the claim that GW170729 is not a population outlier. We also provide non-parametric constraints on the rate of high-mass mergers and conservatively bound the rate of mergers with m1 > 45 M⊙ at {2.8}-2.0+5.4% of the total merger rate. After 100 detections like those of O1 and O2 from a population with a maximum primary mass of 45 M⊙, it would be common for the most massive system to have an observed maximum-likelihood mass m1 ≳ 70 M⊙.

Keywords: astrophysical black holes; gravitational wave astronomy; astronomy data analysis; hierarchical models
Studying the Reflection Spectra of the New Black Hole X-Ray Binary Candidate MAXI J1631-479 Observed by NuSTAR: A Variable Broad Iron Line Profile

We present results from the Nuclear Spectroscopic Telescope Array observations of the new black hole X-ray binary candidate MAXI J1631-479 at two epochs during its 2018-2019 outburst, which caught the source in a disk dominant state and a power-law dominant state. Strong relativistic disk reflection features are clearly detected, displaying significant variations in the shape and strength of the broad iron emission line between the two states. Spectral modeling of the reflection spectra reveals that the inner radius of the optically thick accretion disk evolves from <1.9 ${r}_{{\rm{g}}}$ to 12 ± 1 rg (statistical errors at 90% confidence level) from the disk dominant to the power-law dominant state. Assuming in the former case that the inner disk radius is consistent with being at the innermost stable circular orbit, we estimate a black hole spin of a* > 0.94. Given that the bolometric luminosity is similar in the two states, our results indicate that the disk truncation observed in MAXI J1631-479 in the power-law dominant state is unlikely to be driven by a global variation in the accretion rate. We propose that it may instead arise from local instabilities in the inner edge of the accretion disk at high accretion rates. In addition, we find an absorption feature in the spectra centered at 7.33 ± 0.03 keV during the disk dominant state, which is evidence for the rare case that an extremely fast disk wind ( ${V}_{\mathrm{out}}={0.067}_{-0.004}^{+0.001}\,c$ ) is observed in a low-inclination black hole binary, with the viewing angle of 29° ± 1° as determined by the reflection modeling.

Keywords: accretion; black hole physics; x-ray binary stars; x-ray transient sources
Evolution of the Heliotail Lobes over a Solar Cycle as Measured by IBEX

Energetic neutral atom (ENA) measurements by IBEX reveal that the heliotail comprises an energy-dependent multilobe structure. We examine the heliotail evolution over 11 yr of IBEX observations covering a full solar cycle (SC). We find the following: (1) The heliotail structure persists over the entire SC, comprising three ENA-enhanced and two ENA-suppressed lobes. (2) Lobe sizes and locations are generally stable but exhibit variations in ENA fluxes driven by the SC. (3) Lobe centers follow a cyclic behavior over multiple SC phases, indicating direct signatures of slow and fast solar wind (SW) interactions in the inner heliosheath (IHS). (4) The tilted plane passing through the port-starboard lobes' centers oscillates in latitude but maintains its tilt from the ecliptic plane, likely a consequence of the interstellar magnetic field draping around the heliosphere. (5) The transition of the central heliotail from a single lobe at ~1.1 keV to two lobes above ~2 keV is SC-dependent and directly reflects the IHS plasma properties, i.e., when ENA fluxes from fast SW from the polar coronal holes change over time. (6) The central lobe exhibits a substructure that is enhanced and offset from the downwind direction, possibly indicating an asymmetric ENA emission or an asymmetry in the parent plasma distribution. These results reveal the general stability of the heliotail structure over time and distinct variations in individual lobes' properties in relation to the SC phases. Furthermore, results show the effects of multiple SC phases in the tail, reflecting different ENA travel times and source histories.

Keywords: heliosphere; the sun; charge exchange ionization; solar cycle; interstellar medium; solar wind