adsabs/SciX_UAT_keywords huggingface dataset:
Lost in Space: Companions' Fatal Dance around Massive Dying Stars

Discoveries of planet and stellar remnant hosting pulsars challenge our understanding, as the violent supernova explosion that forms the pulsar presumably destabilizes the system. Type II supernova explosions lead to the formation of eccentric bound systems, free-floating planets, neutron stars, pulsars, and white dwarfs. Analytical and numerical studies of high mass-loss rate systems based on perturbation theory so far have focused mainly on planet-star systems. In this paper, we extend our understanding of the fate of planet-star and binary systems by assuming a homologous envelope expansion model using a plausible ejection velocity (1000-10,000 km s-1), and envelope and neutron star masses. The investigation covers secondary masses of 1-10 M J for planetary companions and 1-20 M ⊙ for stellar companions. We conduct and analyze over 2.5 million simulations assuming different semimajor axes (2.23-100 au), eccentricities (0-0.8), and true anomalies (0-2π) for the companion. In a homologous expansion scenario, we confirm that the most probable outcome of the explosion is the destabilization of the system, while the retention of a bound system requires a highly eccentric primordial orbit. In general, a higher ejecta velocity results in a lower eccentricity orbit independent of secondary mass. The explanation of close-in pulsar planets requires exotic formation scenarios, rather than survival through the type II supernova explosion model. Postexplosion bound star systems gain a peculiar velocity (<100 km s-1), even though the explosion model is symmetric. The applied numerical model allows us to derive velocity components for dissociating systems. The peculiar velocities of free-floating planets and stellar corpses are in the range of 10-6-275 km s-1.

Keywords: exoplanet dynamics
Deneb Is a Large-amplitude Polarimetric Variable

We write to report the discovery that Deneb is a large-amplitude polarization variable. Over a ∼400 days time span from 2022 August Deneb's polarization was typically around 3900 parts per million (ppm) in the SDSS band. Yet, it varied by several hundred parts per million in an irregular way on a timescale of weeks. The largest polarization change, amounting to 2500 ppm, occurred shortly after the last pulsation "resumption" event identified by Abt et al. in TESS photometry. The relationship between the observed polarization—particularly corresponding to the resumption event—and its brightness and H α spectra suggests a mechanism involving density changes in its wind and/or extended atmosphere. Smaller effects due to pulsations are not ruled out, and further study is recommended.

Keywords: polarimetry; alpha cygni variable stars; starlight polarization
Three-dimensional Velocity Diagnostics to Constrain the Type Ia Origin of Tycho's Supernova Remnant

While various methods have been proposed to disentangle the progenitor system for Type Ia supernovae, their origin is still unclear. A circumstellar environment is key to distinguishing between the double-degenerate and single-degenerate (SD) scenarios since a dense wind cavity is expected only in the case of the SD system. We perform spatially resolved X-ray spectroscopy of Tycho's supernova remnant (SNR) with XMM-Newton and reveal the three-dimensional velocity structure of the expanding shock-heated ejecta measured from Doppler-broadened lines of intermediate-mass elements. Obtained velocity profiles are fairly consistent with those expected from a uniformly expanding ejecta model near the center, whereas we discover a rapid deceleration (∼4000 to ∼1000 km s‑1) near the edge of the remnant in almost every direction. The result strongly supports the presence of a dense wall entirely surrounding the remnant, which is confirmed also by our hydrodynamical simulation. We thus conclude that Tycho's SNR is likely of SD origin. Our new method will be useful for understanding progenitor systems of Type Ia SNRs in the era of high-angular/energy-resolution X-ray astronomy with microcalorimeters.

Keywords: supernova remnants
Rotational Phase Dependent J - H Colour of the Dwarf Planet Eris

The largest bodies-or dwarf planets-constitute a different class among Kuiper Belt objects and are characterized by bright surfaces and volatile compositions remarkably different from that of smaller trans-Neptunian objects. These compositional differences are also reflected in the visible and near-infrared colors, and variegations across the surface can cause broadband colors to vary with rotational phase. Here we present near-infrared J and H-band observations of the dwarf planet (136199) Eris obtained with the GuideDog camera of the Infrared Telescope Facility. These measurements show that-as suspected from previous J - H measurements-the J - H color of Eris indeed varies with rotational phase. This suggests notable surface heterogenity in chemical composition and/or other material properties despite the otherwise quite homogeneous, high albedo surface, characterized by a very low amplitude visible range light curve. While variations in the grain size of the dominant CH4 may in general be responsible for notable changes in the J - H color, in the current observing geometry of the system it can only partially explain the observed J - H variation. *Visiting Astronomer at the Infrared Telescope Facility, which is operated by the University of Hawaii under contract 80HQTR19D0030 with the National Aeronautics and Space Administration.

Keywords: photometry; trans-neptunian objects; near infrared astronomy
Enhanced Three-minute Oscillation above a Sunspot during a Solar Flare

Three-minute oscillations are a common phenomenon in the solar chromosphere above a sunspot. Oscillations can be affected by the energy release process related to solar flares. In this paper, we report on an enhanced oscillation in flare event SOL2012-07-05T21:42 with a period of around 3 minutes that occurred at the location of a flare ribbon at a sunspot umbral–penumbral boundary and was observed in both chromospheric and coronal passbands. An analysis of this oscillation was carried out using simultaneous ground-based observations from the Goode Solar Telescope at the Big Bear Solar Observatory and space-based observations from the Solar Dynamics Observatory. A frequency shift was observed before and after the flare, with the running penumbral wave that was present with a period of about 200 s before the flare coexisting with a strengthened oscillation with a period of 180 s at the same locations after the flare. We also found a phase difference between different passbands, with the oscillation occurring from high-temperature to low-temperature passbands. Theoretically, the change in frequency was strongly dependent on the variation of the inclination of the magnetic field and the chromospheric temperature. Following an analysis of the properties of the region, we found the frequency change was caused by a slight decrease of the magnetic inclination angle with respect to the local vertical. In addition, we suggest that the enhanced 3 minute oscillation was related to the additional heating, maybe due to the downflow, during the EUV late phase of the flare.

Keywords: active solar chromosphere; solar oscillations; solar flares
Revised Radiative Response Coefficients for the Curiosity Rover Mastcam from Direct Solar Images and Analog Tests

We have used solar images taken by the Curiosity rover's Mastcam to derive new radiometric response coefficients. In addition, we used calibration data from the Perseverance rover's Mastcam-Z instrument, which used the same detector, to estimate temperature sensitivity of the radiative response. The new coefficients allow calibration of raw data to radiance using the illuminant (the Sun) as the calibration source. Compared to the original pre-flight and early in-flight calibration, the revised calibration is expected to be more consistent across instrument temperature and allow for a self-consistent conversion to radiance factor values when contemporaneous calibration target images are not available or not appropriate. The revised coefficients were incorporated in a recalibration of Mastcam radiance products.

Keywords: mars; space vehicle instruments; calibration
New Pulsating Variable Stars and Eclipsing Binaries in NGC 6871

Leveraging publicly available Transiting Exoplanet Survey Satellite data, I conducted a small regional survey centered on the δ Scuti star V1821 Cyg in the open cluster NGC 6871, spanning a radius of 1°. This survey yielded a remarkable 1530 newly classified variable stars, encompassing: 198 eclipsing binary systems, 12 of which exhibit pulsating or rotating components, 105 γ Doradus stars, 116 δ Scuti stars, 526 rotating variable stars, and dozens of other types. It is not surprising that no RR Lyrae stars were found in this particular young open cluster. *Dedicated to my wife Jingyun Zhang.

Keywords: pulsating variable stars; delta scuti variable stars; gamma doradus variable stars; eclipsing binary stars
UV-optical Emission of AB Aur b Is Consistent with Scattered Stellar Light

The proposed protoplanet AB Aur b is a spatially concentrated emission source imaged in the millimeter-wavelength disk gap of the Herbig Ae/Be star AB Aur. Its near-infrared spectrum and absence of strong polarized light have been interpreted as evidence supporting the protoplanet interpretation. However, the complex scattered-light structures in the AB Aur disk pose challenges in resolving the emission source and interpreting the true nature of AB Aur b. We present new images of the AB Aur system obtained using the Hubble Space Telescope Wide Field Camera 3 in the ultraviolet (UV) and optical bands. AB Aur b and the known disk spirals are recovered in the F336W, F410M, and F645N bands. The spectral energy distribution of AB Aur b shows absorption in the Balmer jump, mimicking that of early-type stars. By comparing the colors of AB Aur b to those of the host star, the disk spirals, and predictions from scattered light and self-luminous models, we find that the emission from AB Aur b is inconsistent with planetary photospheric or accretion shock models. Instead, it is consistent with those measured in the circumstellar disks that trace scattered light. We conclude that the UV and visible emission from AB Aur b does not necessitate the presence of a protoplanet. We synthesize observational constraints on AB Aur b and discuss inconsistent interpretations among different data sets. Considering the significance of the AB Aur b discovery, we advocate for further observational evidence to verify its planetary nature.

Keywords: hubble space telescope; exoplanets; protoplanetary disks; direct imaging; hst photometry; ultraviolet color
A Mass-Magnitude Relation for Low-mass Stars Based on Dynamical Measurements of Thousands of Binary Star Systems

Stellar mass is a fundamental parameter that is key to our understanding of stellar formation and evolution, as well as the characterization of nearby exoplanet companions. Historically, stellar masses have been derived from long-term observations of visual or spectroscopic binary star systems. While advances in high-resolution imaging have enabled observations of systems with shorter orbital periods, measurements of stellar masses remain challenging, and relatively few have been precisely measured. We present a new statistical approach to measuring masses for populations of stars. Using Gaia astrometry, we analyze the relative orbital motion of >3800 wide binary systems comprising low-mass stars to establish a mass-magnitude relation in the Gaia G RP band spanning the absolute magnitude range 14.5 > ${M}_{{G}_{\mathrm{RP}}}$ > 4.0, corresponding to a mass range of 0.08 M ⊙ ≲ M ≲ 1.0 M ⊙. This relation is directly applicable to >30 million stars in the Gaia catalog. Based on comparison to existing mass-magnitude relations calibrated for K s magnitudes from the Two Micron All Sky Survey, we estimate that the internal precision of our mass estimates is ~10%. We use this relation to estimate masses for a volume-limited sample of ~18,200 stars within 50 pc of the Sun and the present-day field mass function for stars with M ≲ 1.0 M ⊙, which we find peaks at 0.16 M ⊙. We investigate a volume-limited sample of wide binary systems with early-K dwarf primaries, complete for binary mass ratios q > 0.2, and measure the distribution of q at separations >100 au. We find that our distribution of q is not uniform, rather decreasing toward q = 1.0.

Keywords: binary stars; stellar masses; astrostatistics
Series of Small-scale Low Plasma β Magnetic Flux Ropes Originating from the Same Longitudinal Region: Parker Solar Probe Observations

In this study, we report on small-scale magnetic flux ropes (SMFRs) observed as a compact series in a narrow Carrington longitudinal range during three Parker Solar Probe (PSP) encounters. First, during ~1.5 days of PSP's inbound part of Encounter 4, we identified a series of 11 SMFRs within 1.°4 in longitude over the radial distance of ~8.4 R ☉ (from ~44 to 35 R ☉). The identified SMFRs lasted from ~0.5 to 1.8 hr, and adjacent events were separated mostly by a few hours and up to ~6.5 hr at the longest, but some events were very closely spaced with intervals of a few ~tens of minutes or less apart. Most of the identified SMFRs are successfully fitted to the force-free model. The SMFRs are clearly distinguished from the surroundings by a notable reduction in plasma β, which itself was comparably low (less than unity) in the background plasma. Furthermore, the magnetic field and plasma flow within the SMFRs fluctuated significantly less than the more turbulent surroundings. The fluctuations in the surrounding medium exhibited occasional Br polarity reversal (possibly switchbacks) and were Alfvénic to a large extent with far weaker compressional components. The majority of these key features with some differences have also been found in the series of SMFRs and their surroundings identified within 1.°3 or less in longitude during Encounters 1 and 5. We speculate that these SMFRs were repetitively generated by successive reconnection within a very narrow angular zone located close to the Sun but not necessarily at the same radial position.

Keywords: solar wind; solar magnetic reconnection
Power-law Distribution of Solar Cycle-modulated Coronal Jets

Power-law distributions have been studied as a significant characteristic of nonlinear dissipative systems. Since discovering the power-law distribution of solar flares that was later extended to nanoflares and stellar flares, it has been widely accepted that different scales of flares share the same physical process. Here we present the newly developed semiautomated jet identification algorithm and its application for detecting more than 1200 off-limb solar jets during Solar Cycle 24. Power-law distributions have been revealed between the intensity/energy and frequency of these events, with indices found to be analogous to those for flares and coronal mass ejections (CMEs). These jets are also found to be spatially and temporally modulated by the solar cycle, forming a butterfly diagram in their latitudinal-temporal evolution, experiencing quasi-annual oscillations in their analyzed properties, and very likely gathering in certain active longitudinal belts. Our results show that coronal jets display the same nonlinear behavior as that observed in flares and CMEs, in solar and stellar atmospheres, strongly suggesting that they result from the same nonlinear statistics of scale-free processes as their counterparts in different scales of eruptive events. Although these jets, like flares and other large-scale dynamic phenomena, are found to be significantly modulated by the solar cycle, their corresponding power-law indices still remain similar.

Keywords: solar cycle; solar coronal transients; solar atmosphere; the sun
Double-peaked Pulse Profile of FRB 200428: Synchrotron Maser Emission from Magnetized Shocks Encountering a Density Jump

Very recently a fast radio burst (FRB) 200428 associated with a strong X-ray burst from the Galactic magnetar SGR 1935+2154 was detected; this provides direct evidence supporting the magnetar progenitor models of FRBs. Assuming that the FRB radiation mechanism is synchrotron maser emission from magnetized shocks, we develop a specific scenario by introducing a density-jump structure of upstream medium, thus making the double-peaked character of FRB 200428 a natural outcome. The luminosity and emission frequency of two pulses can be well explained in this scenario. Furthermore, we find that the synchrotron emission of shock-accelerated electrons is in the X-ray band, and therefore can be responsible for at least a portion of observed X-ray fluence. With the proper upgrade, in the future this density-jump scenario could be applied to FRBs with multiple peaks.

Keywords: radio transient sources; neutron stars; magnetars
Giant Metrewave Radio Telescope Detection of HI 21 cm Emission from Star-forming Galaxies at z ≈ 1.3

We report a ≈400 hr Giant Metrewave Radio Telescope (GMRT) search for HI 21 cm emission from star-forming galaxies at z = 1.18-1.39 in seven fields of the DEEP2 Galaxy Survey. Including data from an earlier 60 hr GMRT observing run, we co-added the HI 21 cm emission signals from 2841 blue star-forming galaxies that lie within the FWHM of the GMRT primary beam. This yielded a 5.0σ detection of the average HI 21 cm signal from the 2841 galaxies at an average redshift <z> ≈ 1.3, only the second detection of HI 21 cm emission at z ≥ 1. We obtain an average HI mass of <MHI> = (3.09 ± 0.61) × 1010 M⊙ and an HI-to-stellar mass ratio of 2.6 ± 0.5, both significantly higher than values in galaxies with similar stellar masses in the local universe. We also stacked the 1.4 GHz continuum emission of the galaxies to obtain a median star formation rate (SFR) of 14.5 ± 1.1 M⊙yr-1. This implies an average HI depletion timescale of ≈2 Gyr for blue star-forming galaxies at z ≈ 1.3, a factor of ≈3.5 lower than that of similar local galaxies. Our results suggest that the HI content of galaxies toward the end of the epoch of peak cosmic SFR density is insufficient to sustain their high SFR for more than ≈2 Gyr. Insufficient gas accretion to replenish the HI could then explain the observed decline in the cosmic SFR density at z < 1.

Keywords: radio spectroscopy; neutral hydrogen clouds; galaxy evolution
Building Robust Active Galactic Nuclei Mock Catalogs to Unveil Black Hole Evolution and for Survey Planning

The statistical distributions of active galactic nuclei (AGNs), i.e., accreting supermassive black holes (BHs), in mass, space, and time are controlled by a series of key properties, namely, the BH-galaxy scaling relations, Eddington ratio distributions, and fraction of active BH (duty cycle). Shedding light on these properties yields strong constraints on the AGN triggering mechanisms while providing a clear baseline to create useful mock catalogs for the planning of large galaxy surveys. Here we delineate a robust methodology to create mock AGN catalogs built on top of large N-body dark matter simulations via state-of-the-art semiempirical models. We show that by using as independent tests the AGN clustering at fixed X-ray luminosity, galaxy stellar mass, and BH mass, along with the fraction of AGNs in groups and clusters, it is possible to significantly narrow down the choice in the relation between BH mass and host galaxy stellar mass, the duty cycle, and the average Eddington ratio distribution, delivering well-suited constraints to guide cosmological models for the coevolution of BHs and galaxies. Avoiding such a step-by-step methodology inevitably leads to strong degeneracies in the final mock catalogs, severely limiting their usefulness in understanding AGN evolution and in survey planning and testing.

Keywords: active galactic nuclei; active galaxies; x-ray active galactic nuclei; agn host galaxies; large-scale structure of the universe
A Smoking Gun for Planetesimal Formation: Charge-driven Growth into a New Size Range

Collisions electrically charge grains, which promotes growth by coagulation. We present aggregation experiments with three large ensembles of basalt beads (150-180 μm), two of which are charged, while one remains almost neutral as a control system. In microgravity experiments, free collisions within these samples are induced with moderate collision velocities (0-0.2 m s-1). In the control system, coagulation stops at (sub-)mm size while the charged grains continue to grow. A maximum agglomerate size of 5 cm is reached, limited only by bead depletion in the free volume. For the first time, charge-driven growth well into the centimeter range is directly proven by experiments. In protoplanetary disks, this agglomerate size is well beyond the critical size needed for hydrodynamic particle concentration as, e.g., by the streaming instabilities.

Keywords: planet formation; protoplanetary disks
On the Kink Instability of Twisted Coronal Loops: Nonneutralized Electric Current

Based on linear magnetohydrodynamic equations and an energy principle we analyze the ideal kink instability of a twisted force-free coronal loop (flux rope) surrounded by an outer potential magnetic field by using the sharp-boundary approximation at the surface. Unlike Tsap et al., a magnetic flux rope with nonneutralized (uncompensated) electric current is considered. We have shown that the twist angle of magnetic field lines is closely related to coronal mass ejections and solar flares. The kink instability condition does not depend on the radial profile of the magnetic field inside a flux rope in the long-wavelength limit but depends strongly on the reverse electric currents at the surface. The total critical twist angle of magnetic field lines, which determines the kink instability threshold, can be much greater than π radians due to reverse azimuthal surface current. This agrees with observations and illustrates the importance of the role of reverse currents for stabilization of a flux rope. Additional arguments in favor of the energy release models based on the uncompensated electric currents are presented.

Keywords: active solar corona
Cosmic Velocity Field Reconstruction Using AI

We develop a deep-learning technique to infer the nonlinear velocity field from the dark matter density field. The deep-learning architecture we use is a "U-net" style convolutional neural network, which consists of 15 convolution layers and 2 deconvolution layers. This setup maps the three-dimensional density field of 323 voxels to the three-dimensional velocity or momentum fields of 203 voxels. Through the analysis of the dark matter simulation with a resolution of 2h-1 Mpc, we find that the network can predict the the nonlinearity, complexity, and vorticity of the velocity and momentum fields, as well as the power spectra of their value, divergence, and vorticity and its prediction accuracy reaches the range of k ≃ 1.4 h Mpc-1 with a relative error ranging from 1% to ≲10%. A simple comparison shows that neural networks may have an overwhelming advantage over perturbation theory in the reconstruction of velocity or momentum fields.

Keywords: large-scale structure of the universe; cosmic web; dark matter distribution; cosmology; astrostatistics