adsabs/SciX_UAT_keywords huggingface dataset:
A High-resolution Spectroscopic Analysis of Aminoacrylonitrile and an Interstellar Search toward G+0.693

Cyanides, ranging from three carbon atoms to polycyclic aromatic hydrocarbons, and alkenyl compounds are abundant in the interstellar medium. Aminoacrylonitrile (3-Amino-2-propenenitrile, H2N-CH=CH-C≡N), an alkenyl cyanide, thus represents a promising candidate for new interstellar detection. A comprehensive spectroscopic laboratory investigation of aminoacrylonitrile in its rotational ground vibrational state has been herein performed. The measurements carried out up to the THz regime made it possible to generate a precise set of reliable rest frequencies for its search in space up to submillimeter wavelengths. The Z-aminoacrylonitrile (Z-apn) isomer spectrum has been recorded employing a source-modulated submillimeter spectrometer, from 80 GHz to 1 THz. A combination of Doppler and sub-Doppler measurement regimes allowed one to record 600 new lines. The collected data have enabled the characterization of a set of spectroscopic parameters up to decic centrifugal distortion constants. The catalog generated from the improved spectral data has been used for the search of Z-apn in the spectral survey of the G+0.693-0.027 molecular cloud located in the central molecular zone, in the proximity of the Galactic center.

Keywords: molecular spectroscopy; laboratory astrophysics; pre-biotic astrochemistry; complex organic molecules; spectral line identification; interstellar abundances; interstellar medium; interstellar molecules; molecular clouds
Investigating the Chromospheric Footpoints of the Solar Wind

Coronal holes present the source of the fast solar wind. However, the fast solar wind is not unimodal—there are discrete, but subtle, compositional, velocity, and density structures that differentiate different coronal holes as well as wind streams that originate within one coronal hole. In this Letter we exploit full-disk observational "mosaics" performed by the Interface Region Imaging Spectrograph (IRIS) spacecraft to demonstrate that significant spectral variation exists within the chromospheric plasma of coronal holes. The spectral differences outline the boundaries of some—but not all—coronal holes. In particular, we show that the "peak separation" of the Mg II h line at 2803 Å illustrates changes in what appear to be open magnetic features within a coronal hole. These observations point to a chromospheric source for the inhomogeneities found in the fast solar wind. These chromospheric signatures can provide additional constraints on magnetic field extrapolations close to the source, potentially on spatial scales smaller than from traditional coronal hole detection methods based on intensity thresholding in the corona. This is of increased importance with the advent of Parker Solar Probe and Solar Orbiter and the ability to accurately establish the connectivity between their in situ measurements and remote sensing observations of the solar atmosphere.

Keywords: quiet solar chromosphere; solar magnetic fields; solar coronal holes; solar corona
Suspended and Restored Activities of a Nearby Supermassive Black Hole

The discovery of spectral type transition of active galactic nuclei (AGNs), the so-called "changing-look" (CL) phenomenon, challenges the widely accepted AGN paradigm, not only in the orientation-based unified model, but also in the standard disk model. In past decades, only a couple of nearby repeat changing-look active galactic nuclei (CL-AGNs) have been identified. Here we report spectroscopic observations of UGC 3223 over the course of 18 yr, from 2001 onwards. Combining the spectrum taken in 1987 by Stirpe, we have witnessed its type transitions from $1.5\to 2.0\to 1.8$ over 32 yr, and captured a long-lived (at least 10 yr) thorough "turn-off" state with a spectrum typical of a Seyfert 2 galaxy. The long-term thorough turn-off state probably suggests a once-dormant and an awakening central engine in UGC 3223. We argue that the (dis)appearance of the broad Balmer emission lines can be explained by the disk-wind broad-line region model given the evolution of the calculated Eddington ratio of accretion of the supermassive black hole.

Keywords: active galactic nuclei; emission line galaxies
TESS Observations of the Luhman 16 AB Brown Dwarf System: Rotational Periods, Lightcurve Evolution, and Zonal Circulation

Brown dwarfs were recently found to display rotational modulations, commonly attributed to cloud cover of varying thickness, possibly modulated by planetary-scale waves. However, the long-term, continuous, high-precision monitoring data to test this hypothesis for more objects is lacking. By applying our novel photometric approach to Transiting Exoplanet Survey Satellite data, we extract a high-precision lightcurve of the closest brown dwarfs, which form the binary system Luhman 16 AB. Our observations, which cover about 100 rotations of Luhman 16 B, display continuous lightcurve evolution. The periodogram analysis shows that the rotational period of the component that dominates the lightcurve is 5.28 hr. We also find evidence for periods of 2.5, 6.94, and 90.8 hr. We show that the 2.5 and 5.28 hr periods emerge from Luhman 16 B and that they consist of multiple, slightly shifted peaks, revealing the presence of high-speed jets and zonal circulation in this object. We find that the lightcurve evolution is well fit by the planetary-scale waves model, further supporting this interpretation. We argue that the 6.94 hr peak is likely the rotation period of Luhman 16 A. By comparing the rotational periods to observed v sin(i) measurements, we show that the two brown dwarfs are viewed at angles close to their equatorial planes. We also describe a long-period (P ∼ 91 hr) evolution in the lightcurve, which we propose emerges from the vortex-dominated polar regions. Our study paves the way toward direct comparisons of the predictions of global circulation models to observations via periodogram analysis. * Based on observations collected with the NASA TESS.

Keywords: exoplanet atmospheres; atmospheric circulation; t dwarfs; atmospheric variability; stellar rotation; photometry
Spectroscopic Detection of Alfvénic Waves in the Chromosphere of Sunspot Regions

Transverse magnetohydrodynamic waves often called Alfvénic (or kink) waves have been often theoretically put forward to solve the outstanding problems of the solar corona like coronal heating, solar wind acceleration, and chemical abundance enhancement. Here we report the first spectroscopic detection of Alfvénic waves around a sunspot at chromospheric heights. By analyzing the spectra of the Hα line and Ca II 854.2 nm line, we determined line-of-sight velocity and temperature as functions of position and time. As a result, we identified transverse magnetohydrodynamic waves pervading the superpenumbral fibrils. These waves are characterized by the periods of 2.5 to 4.5 minutes, and the propagation direction parallel to the fibrils, the supersonic propagation speeds of 45 to 145 km s-1, and the close association with umbral oscillations and running penumbral waves in sunspots. Our results support the notion that the chromosphere around sunspots abounds with Alfvénic waves excited by the mode conversion of the upward-propagating slow magnetoacoustic waves.

Keywords: sunspots; magnetohydrodynamics; alfven waves; solar chromosphere; solar atmosphere
The Asteroseismology Analysis of 14 Solar-like Stars Based on TESS and LAMOST Observations

The Transiting Exoplanet Survey Satellite (TESS) is performing a near all-sky survey for planets that transit bright stars. It provides excellent photometric data for asteroseismology of solar-like stars that exhibit oscillation by a convection-driven mechanism. In this paper, we analyze the light curves of 14 stars that are observed by TESS. These stars mainly focus on Sector 21 and the other Sectors intersecting with Sector 21. Through crossmatching with the LAMOST surveys, 14 stars with signals of solar-like oscillations are selected, and asteroseismic analysis is present. The frequency of maximum power ${\nu }_{\max }$ and the large frequency separation Δν are extracted from its frequency power spectrum using the pySYD pipeline. Scaling relations are an attractive method that can easily and immediately be applied to observations to derive the stellar properties. To validate the different calibrated scaling relations for 14 TESS stars, the fundamental stellar properties are estimated by the relations and compared with grid-based modeling results, which use the constraints of global asteroseismic parameters and nonasteroseismic parameters. The new red-giant branch (RGB) scaling relations are found to overestimate the radius and mass when compared to the grid results, while the f Δν scaling relations lead to overall lower radius and mass estimates. The average uncertainties of these stars from grid modeling are within 2% in the radius and 3% in the mass. Regardless of the method, we can get almost equally good results of log g for all the stars. Besides the grid method, the new RGB scaling relations for ages provide a simple and accurate method to determine the stellar ages.

Keywords: asteroseismology; stellar structures; stellar pulsations; stellar oscillations; rapid stellar oscillations; stellar properties
The Dynamic Response of Jovian Magnetotail Reconnection to Enhanced Solar Wind Ram Pressure

In this study, we employ the Grid Agnostic Magnetohydrodynamic (MHD) for Extended Research Applications (GAMERA), a high-resolving-power, three-dimensional global MHD model, to simulate magnetotail reconnection in Jupiter's magnetosphere. While previous satellite observations have provided initial statistics on magnetotail reconnection properties at Jupiter, they have been limited in spacetime coverage, leaving the dynamic process of Jovian magnetotail reconnection and its response to the solar wind (SW) poorly understood. Using MHD simulations, we quantitatively analyze the temporal evolution and spatial dependence of nightside reconnection in Jupiter's magnetotail under ideal quiet and enhanced SW conditions. Our results demonstrate that magnetotail reconnection tends to occur in the midnight and postmidnight sectors, with a low occurrence in the premidnight sector, consistent with both Galileo and Juno observations and predictions by Delamere & Bagenal. The magnetic local time (MLT)–radial distribution of magnetotail reconnection is broad, indicating that Jovian magnetotail reconnection is always dynamic rather than steady state. Enhanced SW ram pressure can decrease the MLT coverage of magnetotail reconnection by compressing Jupiter's magnetosphere. However, the occurrence of magnetotail reconnection near the midnight and postmidnight sectors is enhanced by SW compression beyond 60 R J, but is not significantly impacted by SW compression within 60 R J. Conversely, SW compression suppresses reconnection in the premidnight sector, leading to a stronger dawn–dusk asymmetry in the occurrence and location of magnetotail reconnection. This study validates the applicability of the GAMERA code for simulating Jupiter's magnetosphere and provides complementary insights into the dynamic structure and the SW response of Jupiter's magnetosphere.

Keywords: jupiter; planetary magnetospheres
Constraining Protoplanetary Disk Winds from Forbidden Line Profiles with Simulation-based Inference

Protoplanetary disks (PPDs) are sites of vigorous hydrodynamic processes, such as accretion and outflows, and ultimately establish the conditions for the formation of planets. The properties of disk outflows are often inferred through the analysis of forbidden emission lines. These lines contain multiple overlapping components, tracing different emission regions with different processes that excite them: a high-velocity component (tracing a jet), a broad low-velocity component (LVC; tracing inner disk wind), and a narrow LVC (tracing the outer disk wind). They are also heavily contaminated by background spectral features. All of these challenges call into question the traditional approach of fitting Gaussian components to the line profiles and cloud the physical interpretation of those components. We introduce a novel statistical technique to analyze emission lines in PPDs. Simulation-based inference is a computationally efficient machine-learning technique that produces posterior distributions of the parameters (e.g., magnetic field, radiation sources, and geometry) of a representative wind model when given a spectrum without any prior assumption about line shapes (e.g., symmetry). In this pathfinder study, we demonstrate that this technique indeed accurately recovers the parameters from simulated spectra without noise and background. Future work will provide an analysis of the observed spectra.

Keywords: spectroscopy; convolutional neural networks; protoplanetary disks
Disk Wind-Driven Expanding Radio-emitting Shell in Tidal Disruption Events

We study the evolution of a nonrelativistically expanding thin shell in radio-emitting tidal disruption events (TDEs) based on a one-dimensional spherically symmetric model considering the effect of both a time-dependent mass-loss rate of the disk wind and the ambient mass distribution. The analytical solutions are derived in two extreme limits; one is the approximate solution near the origin in the form of the Taylor series, and the other is the asymptotic solution in which the ambient matter is dominant far away from the origin. Our numerical solutions are confirmed to agree with the respective analytical solutions. We find that no simple power law of the time solution exists in early to middle times because the mass-loss rate varies over time, affecting the shell dynamics. We also discuss the application of our model to the observed radio-emitting TDE, AT 2019dsg.

Keywords: astrophysical black holes; tidal disruption; high energy astrophysics; radio astronomy; radio transient sources; transient sources
Direct N-body Simulations of Satellite Formation around Small Asteroids: Insights from DART's Encounter with the Didymos System

We explore binary asteroid formation by spin-up and rotational disruption considering the NASA DART mission's encounter with the Didymos–Dimorphos binary, which was the first small binary visited by a spacecraft. Using a suite of N-body simulations, we follow the gravitational accumulation of a satellite from meter-sized particles following a mass-shedding event from a rapidly rotating primary. The satellite's formation is chaotic, as it undergoes a series of collisions, mergers, and close gravitational encounters with other moonlets, leading to a wide range of outcomes in terms of the satellite's mass, shape, orbit, and rotation state. We find that a Dimorphos-like satellite can form rapidly, in a matter of days, following a realistic mass-shedding event in which only ∼2%–3% of the primary's mass is shed. Satellites can form in synchronous rotation due to their formation near the Roche limit. There is a strong preference for forming prolate (elongated) satellites, although some simulations result in oblate spheroids like Dimorphos. The distribution of simulated secondary shapes is broadly consistent with other binary systems measured through radar or lightcurves. Unless Dimorphos's shape is an outlier, and considering the observational bias against lightcurve-based determination of secondary elongations for oblate bodies, we suggest there could be a significant population of oblate secondaries. If these satellites initially form with elongated shapes, a yet-unidentified pathway is needed to explain how they become oblate. Finally, we show that this chaotic formation pathway occasionally forms asteroid pairs and stable triples, including coorbital satellites and satellites in mean-motion resonances.

Keywords: asteroid dynamics; asteroid satellites; asteroid rotation; near-earth objects; small solar system bodies; asteroids
The TeV Cosmic-Ray Bump: A Message from the Epsilon Indi or Epsilon Eridani Star?

A recently observed bump in the cosmic-ray (CR) spectrum from 0.3 to 30 TV is likely caused by a stellar bow shock that reaccelerates preexisting CRs, which further propagate to the Sun along the magnetic field lines. Along their way, these particles generate an Iroshnikov-Kraichnan (I-K) turbulence that controls their propagation and sustains the bump. Ad hoc fitting of the bump shape requires six adjustable parameters. Our model requires none, merely depending on three physical unknowns that we constrain using the fit. These are the shock Mach number, M, its size, l⊥, and the distance to it, ζobs. Altogether, they define the bump rigidity R0. With M ≈ 1.5-1.6 and R0 ≈ 4.4 TV, the model fits the data with ≈0.08% accuracy. The fit critically requires the I-K spectrum predicted by the model and rules out the alternatives. These attributes of the fit make an accidental agreement highly unlikely. In turn, the R0 and M derived from the fit impose the distance-size relation on the shock: ζobs(pc) ∼ ${10}^{2}\sqrt{{l}_{\perp }(\mathrm{pc})}$ . For sufficiently large bow shocks, l⊥ = 10-3-10-2 pc, we find the distance of ζobs = 3-10 pc. Three promising stars in this range are the Scholz's Star at 6.8 pc, Epsilon Indi at 3.6 pc, and Epsilon Eridani at 3.2 pc. Based on their current positions and velocities, we propose that Epsilon Indi and Epsilon Eridani can produce the observed spectral bump. Moreover, Epsilon Eridani's position is only ∼6°7 off of the magnetic field direction in the solar neighborhood, which also changes the CR arrival direction distribution. Given the proximity of these stars, the bump appearance may change in a relatively short time.

Keywords: galactic cosmic rays; stellar bow shocks; secondary cosmic rays; interstellar scattering; interstellar magnetic fields
Rapid Evolution of Bald Patches in a Major Solar Eruption

A bald patch (BP) is a magnetic topological feature where U-shaped field lines turn tangent to the photosphere. Field lines threading the BP trace a separatrix surface where reconnection preferentially occurs. Here we study the evolution of multiple, strong-field BPs in AR 12673 during the most intense, X9.3 flare of solar cycle 24. The central BP, located between the initial flare ribbons, largely "disintegrated" within 35 minutes. The more remote, southern BP survived. The disintegration manifested as a 9° rotation of the median shear angle; the perpendicular component of the horizontal field (with respect to the polarity inversion line) changed sign. The parallel component exhibited a step-wise, permanent increase of 1 kG, consistent with previous observations of the flare-related "magnetic imprint." The observations suggest that magnetic reconnection during a major eruption may involve entire BP separatrices, leading to a change of magnetic topology from BPs to sheared arcades.

Keywords: solar flares; solar magnetic reconnection; solar active region magnetic fields
Fast Magnetosonic Waves and Flows in a Solar Prominence Foot: Observations and Modeling

We study recent observations of propagating fluctuations in a prominence foot with Hinode Solar Optical Telescope (SOT) high-resolution observations in Ca II and Hα emission, which we identify as nonlinear fast magnetosonic waves. Here we analyze further the observations of propagating waves and flows with Interface Region Imaging Spectrograph Mg II slit jaw images, in addition to Hinode/SOT Ca II images. We find that the waves have typical periods in the range of 5-11 minutes and wavelengths in the plane of the sky (POS) of about 2000 km, while the flows in narrow threads have a typical speed in the POS of ∼16-46 km s-1. We also detect apparent kink oscillations in the threads with flowing material, and apply coronal seismology to estimate the magnetic field strength in the range of 5-17 G. Using 2.5D MHD we model the combined effects of nonlinear waves and flows on the observed dynamics of the prominence material, and reproduce the propagating and refracting fast magnetosonic waves, as well as standing kink-mode waves in flowing material along the magnetic field. The modeling results are in good qualitative agreement with the observations of the various waves and flows in the prominence foot, further confirming coronal seismology analysis and improving the understanding of the fine-scale dynamics of the prominence material.

Keywords: solar prominences; alfven waves; magnetohydrodynamical simulations
Tidal Distortions in NGC1052-DF2 and NGC1052-DF4: Independent Evidence for a Lack of Dark Matter

Two ultra-diffuse galaxies in the same group, NGC1052-DF2 and NGC1052-DF4, have been found to have little or no dark matter and to host unusually luminous globular cluster populations. Such low-mass diffuse objects in a group environment are easily disrupted and are expected to show evidence of tidal distortions. In this work, we present deep new imaging of the NGC1052 group, obtained with the Dragonfly Telephoto Array, to test this hypothesis. We find that both galaxies show strong position-angle twists and are significantly more elongated at their outskirts than in their interiors. The group's central massive elliptical NGC1052 is the most likely source of these tidal disturbances. The observed distortions imply that the galaxies have a low total mass or are very close to NGC1052. Considering constraints on the galaxies' relative distances, we infer that the dark matter halo masses of these galaxies cannot be much greater than their stellar masses. Calculating pericenters from the distortions, we find that the galaxies are on highly elliptical orbits, with a ratio of pericenter to present-day radius R peri/R 0 ~ 0.1 if the galaxies are dark matter-free and R peri/R 0 ~ 0.01 if they have a normal dark halo. Our findings provide strong evidence, independent of kinematic constraints, that both galaxies are dark matter-deficient. Furthermore, the similarity of the tidal features in NGC1052-DF2 and NGC1052-DF4 strongly suggests that they arose at comparable distances from NGC1052. In Appendix A, we describe sbcontrast, a robust method for determining the surface brightness limits of images.

Keywords: dark matter; galaxy evolution; galaxy structure; low surface brightness galaxies; tidal distortion
The Effect of Environment on the Properties of the Most Massive Galaxies at 0.5 < z < 2.5 in the COSMOS-DASH Field

How the environment influences the most massive galaxies is still unclear. To explore the effects of the environment on morphology and star formation in the most massive galaxies at high redshift, we select galaxies with stellar mass $\mathrm{log}({M}_{\star }/{M}_{\odot })\gt 11$ at 0.5 < z < 2.5 in the COSMOS-DASH field, which is the largest field with near-infrared photometric observations using HST/WFC3 to date. Combining these with the newly published COSMOS2020 catalog, we estimate the localized galaxy overdensity using a density estimator within the Bayesian probability framework. With the overdensity map, no significant environmental dependence is found in the distributions of Sérsic index and effective radius. When we consider the star formation state, galaxies at a lower density are found to have a higher median specific star formation rate (sSFR) at 0.5 < z < 1.5. But for star-forming galaxies only, sSFR is independent of the environment over the whole redshift range, indicating that the primary effect of the environment might be to control the quiescent fraction. Based on these observations, the possible environmental quenching process for these massive galaxies might be mergers.

Keywords: galaxy environments; galaxy structure; galaxy quenching; star formation