adsabs/SciX_UAT_keywords huggingface dataset:
Constrained Reference Star Differential Imaging: Enabling High-fidelity Imagery of Highly Structured Circumstellar Disks

High-contrast imaging presents us with the opportunity to study circumstellar disks and the planets still embedded within them, providing key insights into the formation and evolution of planetary systems. However, the postprocessing techniques that are often needed to suppress stellar halo light typically result in significant and variable loss of circumstellar light, even when using relatively conservative approaches like reference star differential imaging (RDI). We introduce "constrained reference star differential imaging" (constrained RDI), a new class of RDI point-spread-function (PSF) subtraction techniques for systems with circumstellar disks. Constrained RDI utilizes either high-resolution polarized-intensity (PI) images or disk models to severely limit or even eliminate the signal loss due to oversubtraction that is common to RDI. We demonstrate the ability of constrained RDI utilizing polarimetric data to yield an oversubtraction-free detection of the AB Aurigae protoplanetary disk in total intensity. PI-constrained RDI allows us to decisively recover the spectral signature of the confirmed, recently discovered protoplanet, AB Aurigae b. We further demonstrate that constrained RDI can be a powerful analysis tool for soon-to-be-acquired James Webb Space Telescope coronagraphic imaging of disks. In both cases, constrained RDI provides analysis-ready products that enable more detailed studies of disks and more robust verification of embedded exoplanets. * Based on data collected at Subaru Telescope, which is operated by the National Astronomical Observatory of Japan.

Keywords: circumstellar disks; protoplanetary disks; debris disks; direct imaging; exoplanet detection methods; polarimetry; coronagraphic imaging
Can Large-scale Migration Explain the Giant Planet Occurrence Rate?

The giant planet occurrence rate rises with orbital period out to at least ∼300 days. Large-scale planetary migration through the disk has long been suspected to be the origin of this feature, as the timescale of standard Type I migration in a standard solar nebula is longer farther from the star. These calculations also find that typical Jupiter-bearing cores shuttle toward the disk inner edge on timescales orders of magnitude shorter than the gas disk lifetime. The presence of gas giants at myriad distances requires mechanisms to slow large-scale migration. We revisit the migration paradigm by building model occurrence rates to compare to the observations, computing simultaneously the migration of cores, their mass growth by gas accretion, and their gap opening. We show explicitly that the former two processes occur in tandem. Radial transport of planets can slow down significantly once deep gaps are carved out by their interaction with disk gas. Disks are more easily perturbed closer to the star, so accounting for gap opening flattens the final orbital period distribution. To recover the observed rise in occurrence rate, gas giants need to be more massive farther out, which is naturally achieved if their envelopes are dust-free. We find that only a narrow region of parameter space can recover the observed giant planet occurrence rate in orbital period, but not simultaneously the mass distribution of low-eccentricity giant planets. This challenges disk migration as the dominant origin channel of hot and warm Jupiters. Future efforts in characterizing the unbiased mass distribution will place stronger constraints on predictions from migration theory.

Keywords: extrasolar gaseous giant planets; exoplanet dynamics; exoplanet formation
Discrepancy between the Low-frequency Cutoffs of Type III Radio Bursts Based on Simultaneous Observations by WIND and PSP

The cutoff frequency is an important characteristic parameter of type III radio bursts. Employing the radio data of the Parker Solar Probe (PSP) in the encounter phases of its first five orbits, our previous work revealed that the maximum probability distribution of the cutoff frequency f lo (~680 kHz) is remarkably higher than that based on Ulysses and WIND (~100 kHz) investigated by Leblanc et al. and Dulk et al. However, the main influencing factor of the discrepancy is still unknown though the possible reasons are discussed. In this study, we utilize the simultaneous observation by WIND and PSP to analyze statistically the distribution of the cutoff frequency of type III radio bursts, which had not been done before. Based on the automatic Canny edge detection and manual selection, we obtain the f lo of 491 (WIND) and 1194 (PSP) type III bursts from their simultaneous observations in the same solar activity period (from 2019 January 1 to 2020 July 31). The statistical results show that the dominant cutoff frequency measured by PSP (i.e., ~700 kHz) is still significantly higher than that by WIND (i.e., ~100 kHz). This implies that radiation attenuation is the main influencing factor for the difference in the statistical results of the cutoff frequency.

Keywords: galaxy dynamics; interplanetary physics
Constraining the PG 1553+113 Binary Hypothesis: Interpreting Hints of a New, 22 yr Period

PG 1553+113 is a well-known blazar exhibiting evidence of a ∼2.2 yr quasiperiodic oscillation (QPO) in the radio, optical, X-ray, and γ-ray bands. Since QPO mechanisms often predict multiple QPOs, we search for a second QPO in its historical optical light curve covering a century of observations. Despite challenging data quality issues, we find hints of a 21.8 ± 4.7 yr oscillation. On its own, this ∼22 yr period has a modest statistical significance of 1.6σ when accounting for the look-elsewhere effect. However, the joint significance of both the 2.2 and 22 yr periods arising from colored noise alone is ∼3.6σ. The next peak of the 22 yr oscillation is predicted to occur around July 2025. We find that such a ∼10:1 relation between two periods can arise in the gas dynamics of a plausible supermassive black hole binary model of PG 1553+113. While the 22 yr QPO is preliminary, an interpretation of PG 1553+113's two QPOs in this binary model suggests that the binary engine has a mass ratio ≳0.2, an eccentricity ≲0.1, and accretes from a disk with characteristic aspect ratio ∼0.03. The putative binary radiates nHz gravitational waves, but the amplitude is ∼10–100 times too low for detection by foreseeable pulsar timing arrays.

Keywords: bl lacertae objects; gravitational waves; astronomy data analysis
Radiolysis of Ices by Cosmic-Rays: CH4 and H2O Ices Mixtures Irradiated by 40 MeV 58Ni11+ Ions

Physico-chemical modifications induced by swift heavy ions on methane-water (CH4:H2O) ices at 15 K are analyzed. Ice films, at concentrations of (1:3) and (1:15), were irradiated by 40 MeV 58Ni11+ ions. Fourier transform transmission spectroscopy in the mid-range was used to monitor the evolution ices at 15 K as a function of projectile fluence. New IR bands appearing for the irradiated (CH4:H2O) (1:3) ice are attributed to the synthesized molecules: C3H8, HCO, H2CO, CO, CO2, H2O2, HCOOH, CH3OH, C2H5OH, and CH3CHO. For the irradiated (CH4:H2O) (1:15) ice, the abundances of the compounds containing two carbons atoms are lower than those for the (1:3) ice; in contrast, CH3OH and H2O2 abundances increase when compared to the values obtained with the (1:3) ice. After irradiation, the ices were warmed up until 110 K, when the IR spectra reveal features of complex organic molecules. The destruction and formation cross sections and the sputtering yields of the ice mixtures are estimated. These findings provide possible pathways for the occurrence of compounds rich in C, O, and H, which are indeed observed in the cold regions of the universe such as ices in grain mantles of the interstellar medium and circumstellar envelopes.

Keywords: astrochemistry; interstellar molecules; laboratory astrophysics; spectroscopy; surface ices
White Dwarfs in the Era of the LSST and Its Synergies with Space-based Missions

With the imminent start of the Legacy Survey for Space and Time (LSST) at the Vera C. Rubin Observatory and several new space telescopes expected to begin operations later in this decade, both time-domain and wide-field astronomy are on the threshold of a new era. In this paper, we use a new multicomponent model for the distribution of white dwarfs (WDs) in our Galaxy to simulate the WD populations in four upcoming wide-field surveys (i.e., LSST, Euclid, the Roman Space Telescope, and the Cosmological Advanced Survey Telescope for Optical and uv Research) and use the resulting samples to explore some representative WD science cases. Our results confirm that LSST will provide a wealth of information for Galactic WDs, detecting more than 150 million WDs at the final depth of its stacked 10 yr survey. Within this sample, nearly 300,000 objects will have 5σ parallax measurements, and nearly 7 million will have 5σ proper-motion measurements, allowing the detection of the turnoff in the halo WD luminosity function and the discovery of more than 200,000 ZZ Ceti stars. The wide wavelength coverage that will be possible by combining LSST data with observations from Euclid and/or the Roman Space Telescope will also discover WDs with debris disks, highlighting the advantages of combining data between the ground- and space-based missions.

Keywords: white dwarf stars; surveys; star counts
Extension of the Electron Diffusion Region in a Guide Field Magnetic Reconnection at Magnetopause

The structure of the electron diffusion region (EDR) in different plasma regimes is an outstanding question related to magnetic reconnection. Here we report a long EDR that extended at least 20 ion inertial lengths downstream of an X line at the Earth's magnetopause, which was observed by the Magnetospheric Multiscale mission. This EDR was detected in the exhaust of an asymmetric magnetic reconnection with a moderate guide field, the reconnection rate of which was ∼0.1. It corresponds to strong positive energy dissipation (J\cdot E' >0) and enhancement of electron nongyrotropy. The energy dissipation was contributed by the electron jet and non-ideal electric field along the outflow direction, which suggests that the EDR probably plays more important roles in the energy conversion in magnetic reconnection than previously thought. Our result could be a significant step toward fully understanding the structure of the EDR.

Keywords: solar magnetic reconnection; plasma physics; space plasmas; planetary boundary layers
Global Mapping of Fragmented Rocks on the Moon with a Neural Network: Implications for the Failure Mode of Rocks on Airless Surfaces

Failure modes of lunar boulders depend both on rheology and the erosion agents acting in the lunar surface environment. Here, we address the failure modes of lunar boulders and their variations at a quasi-global scale (60°N to S). We deploy a neural network and map a total of ~130,000 fragmented boulders (width > ~10 m) scattered across the lunar surface and visually identify a dozen different disintegration morphologies corresponding to different failure modes. Our findings suggest that before a boulder is catastrophically shattered by an impact, there is an internal weakening period with minor morphological evidence of damage at the rock scale at the resolution of the used imagery. We find that some of the rare pre-shattering morphologies (e.g., fractures) are equivalent to morphologies observed on asteroid Bennu, suggesting that these morphologies on the Moon and on asteroids are likely not diagnostic of their formation mechanism (e.g., meteoroid impact, thermal stresses). In addition, we identify new morphologies such as breccia boulders with an advection-like erosion style. We publicly release the produced fractured boulder catalog along with this paper.

Keywords: selenology; planetary geology; the moon
Accuracy Analysis for Shack–Hartmann Wave Front Sensing with Extended Sources

Correlating the Shack–Hartmann wave front sensor (SH-WFS) with extended targets is widely used in solar adaptive optics systems. This paper aims to introduce a theoretical analysis that evaluates the accuracy of the SH-WFS on extended sources, with a specific focus on the implementation of the Normalized Cross-correlation (NCC) algorithm. To obtain an accurate error description, we utilized the calculation formula of the NCC algorithm to directly express the coordinates of the maximum value in the correlation function matrix. Furthermore, we determined the variance of the centroid position through the error transfer function, which quantifies the measurement error. In comparison with the previous findings of Michau et al., our result exhibits a coefficient disparity, specifically obtaining results 1.5 times higher than their work. The extensive solar granulation simulation and experimental results validate the theoretical error formulas. These error formulas can effectively estimate the accuracy of the SH-WFS, providing a theoretical foundation for the design of optical systems.

Keywords: solar instruments
Propagation Properties of Sunspots Umbral Oscillations in Horizontal and Vertical Directions

We present a study on investigating the propagation characteristics of umbral oscillations in sunspots. In sunspot 1 (located in NOAA AR 12127) with four umbrae, the analysis shows that the oscillations in different umbrae are correlated. The weak correlation (<20%) is attributed to the propagation of umbral oscillations across the umbral boundary to its adjacent umbra in the horizontal direction. We speculate that oscillations in two of the umbrae have a common origin in the sub-photosphere, resulting in a stronger correlation (>30%). Additionally, utilizing the TiO (photosphere), Hα (chromosphere) images provided by BBSO/GST, and the 304 Å (upper chromosphere and lower transition region), 171 Å (upper transition region), 193 Å (corona), and 211 Å (active region corona) images acquired by the Atmospheric Imaging Assembly on board the Solar Dynamics Observatory (SDO), we analyze the vertical propagation of oscillations in the sunspot umbra. Multi-channel observation shows that the umbral oscillations observed in the lower atmosphere of sunspot 1 cannot be detected in the upper atmosphere. However, in sunspot 2 (located in NOAA AR 12132), oscillations in the lower atmosphere can propagate to the upper atmosphere. Using photospheric magnetic field data provided by the Helioseismic and Magnetic Imager on board SDO, potential field extrapolation of the magnetic field for the two sunspots shows that open magnetic field structures allow sunspot oscillations to propagate to higher heights, while closed magnetic field structures do not.

Keywords: sunspots
Cannibals in PARADISE: The Effect of Merging Interplanetary Shocks on Solar Energetic Particle Events

Gradual solar energetic particle (SEP) events are associated with shocks driven by coronal mass ejections (CMEs). The merging of two CMEs (so-called cannibalistic CMEs) and the interaction of their associated shocks has been linked to some of the most powerful solar storms ever recorded. Multiple studies have focused on the observational aspects of these SEP events, yet only a handful have focused on modeling similar CME–CME interactions in the heliosphere using advanced magnetohydrodynamic (MHD) models. This work presents, to our knowledge, the first modeling results of a fully time-dependent 3D simulation that captures both the interaction of two CMEs and its effect on the acceleration and transport of SEPs. This is achieved by using an MHD model for the solar wind and CME propagation together with an integrated SEP model. We perform different simulations and compare the behavior of the energetic protons in three different solar wind environments, where a combination of two SEP-accelerating CMEs are modeled. We find that particle acceleration is significantly affected by the presence of both CMEs in the simulation. Initially, less efficient acceleration results in lower-energy particles. However, as the CMEs converge and their shocks eventually merge, particle acceleration is significantly enhanced through multiple acceleration processes between CME-driven shocks, resulting in higher particle intensities and energy levels.

Keywords: solar energetic particles; space weather; solar particle emission; solar coronal mass ejection shocks
Detection of Fluorine in Hot Extreme Helium Stars

The main objective of this paper is to explore abundances of fluorine in hot extreme helium stars (EHes). Overabundance of fluorine is a characteristic feature for cool EHes and R Coronae Borealis stars and further enforces their close connection. For hot EHes this relationship with the cooler EHes, based on their fluorine abundance is unexplored. We present in this paper the first abundance estimates of fluorine determined from singly ionized fluorine lines (F II) for 10 hot EHe stars from optical spectra. Fluorine abundances were determined using the F II lines in two windows centered at 3505 Å and 3850 Å. Six of the 10 stars show significant enhancement of fluorine similar to the cool EHes. Two carbon-poor hot EHes show no signature of fluorine and have a significant low upper limit for the F abundance. These fluorine abundances are compared with the other elemental abundances observed in these stars, which provide an idea about the formation and evolution of these stars. The trends of fluorine with C, O, and Ne show that significant helium burning after a CO-He white dwarf merger can account for a majority of the observed abundances. Predictions from simulations of white dwarf mergers are discussed in light of the observed abundances.

Keywords: stellar abundances; chemically peculiar stars; hydrogen deficient stars; helium-rich stars
A Lower Bound of Star Formation Activity in Ultra-high-redshift Galaxies Detected with JWST: Implications for Stellar Populations and Radiation Sources

Early results of James Webb Space Telescope observations have delivered bright z ≳ 10 galaxy candidates in greater numbers than expected, enabling construction of rest-frame UV luminosity functions (LFs). The LFs contain key information on the galaxy assembly history, star formation activity, and stellar population of the distant universe. Given an upper bound of the total baryonic mass inflow rate to galaxies from their parent halos estimated from abundance matching, we derive a lower bound on the product of the star formation and UV photon production efficiency in galaxies at each redshift. This stringent constraint requires a high efficiency (≳10%-30%) converting gas into stars, assuming a normal stellar population with a Salpeter-like mass distribution. The efficiency is substantially higher than those of typical nearby galaxies, but is consistent with those seen in starburst galaxies and super-star clusters observed in the nearby universe. Alternatively, the star formation efficiency may be as low as a few percent, which is the average value for the entire galaxy population at z ≃ 6, if the stellar population is metal-free and drawn from a top-heavy mass distribution that produces more intense UV radiation. We discuss several other possible scenarios to achieve the constraint, for instance, energetic radiation produced from compact stellar remnants and quasars, and propose ways to distinguish the scenarios by forthcoming observations.

Keywords: high-redshift galaxies; galaxy formation; quasars; supermassive black holes
Torsional Oscillations in Dynamo Models with Fluctuations and Potential for Helioseismic Predictions of the Solar Cycles

Using a nonlinear mean-field solar dynamo model, we study relationships between the amplitude of the "extended" mode of migrating zonal flows ("torsional oscillations") and magnetic cycles, and investigate whether properties the torsional oscillations in subsurface layers and in the deep convection zone can provide information about the future solar cycles. We consider two types of dynamo models: models with regular variations of the α-effect, and models with stochastic fluctuations, simulating "long-memory" and "short-memory" types of magnetic activity variations. It is found that torsional oscillation parameters, such the zonal acceleration, show a considerable correlation with the magnitude of the subsequent cycles with a time lag of 11-20 yr. The sign of the correlation and the time-lag parameters can depend on the depth and latitude of the torsional oscillations as well as on the properties of long-term ("centennial") variations of the dynamo cycles. The strongest correlations are found for the zonal acceleration at high latitudes at the base of the convection zone. The model results demonstrate that helioseismic observations of the torsional oscillations can be useful for advanced prediction of the solar cycles, 1-2 sunspot cycles ahead.

Keywords: solar cycle; solar rotation; solar dynamo
LATIS: The Stellar Mass-Metallicity Relation of Star-forming Galaxies at z 2.5

We present the stellar mass-stellar metallicity relation for 3491 star-forming galaxies at 2 ≲ z ≲ 3 using rest-frame far-ultraviolet spectra from the Lyα Tomography IMACS Survey (LATIS). We fit stellar population synthesis models from the Binary Population And Spectral Synthesis code (v2.2.1) to medium-resolution (R ~ 1000) and high signal-to-noise (>30 per 100 km s-1 over the wavelength range 1221-1800 Å) composite spectra of galaxies in bins of stellar mass to determine their stellar metallicity, primarily tracing Fe/H. We find a strong correlation between stellar mass and stellar metallicity, with stellar metallicity monotonically increasing with stellar mass at low masses and flattening at high masses (M * ≳ 1010.3 M ⊙). Additionally, we compare our stellar metallicity measurements with the gas-phase oxygen abundance of galaxies at similar redshift and estimate the average [α/Fe] ~ 0.6. Such high α-enhancement indicates that high-redshift galaxies have not yet undergone significant iron enrichment through Type Ia supernovae. Moreover, we utilize an analytic chemical evolution model to constrain the mass loading parameter of galactic winds as a function of stellar mass. We find that as the stellar mass increases, the mass loading parameter decreases. The parameter then flattens or reaches a turning point at around M * ~ 1010.5 M ⊙. Our findings may signal the onset of black-hole-driven outflows at z ~ 2.5 for galaxies with M * ≳ 1010.5 M ⊙.

Keywords: galaxy evolution; metallicity; high-redshift galaxies