adsabs/SciX_UAT_keywords huggingface dataset:
Performance Assessment of the KASI-Deep Rolling Imaging Fast-optics Telescope Pathfinder

In a ΛCDM universe, most galaxies evolve by mergers and accretions, leaving faint and/or diffuse structures, such as tidal streams and stellar halos. Although these structures are a good indicator of galaxies' recent mass assembly history, they have the disadvantage of being difficult to observe due to their low surface brightness (LSB). To recover these LSB features by minimizing the photometric uncertainties introduced by the optical system, we developed a new optimized telescope named K-DRIFT pathfinder, adopting a linear astigmatism free-three mirror system. Thanks to the off-axis design, it is expected to avoid the loss and scattering of light on the optical path within the telescope. To assess the performance of this prototype telescope, we investigate the photometric depth and capability to identify LSB features. We find that the surface brightness limit reaches down to μ r,1σ ~ 28.5 mag arcsec-2 in 10″ × 10″ boxes, enabling us to identify a single stellar stream to the east of NGC 5907. We also examine the characteristics of the point-spread function (PSF) and find that the PSF wing reaches a very low level. Still, however, some internal reflections appear within a radius of ~6' from the center of sources. Despite a relatively small aperture (0.3 m) and short integration time (2 hr), this result demonstrates that our telescope is highly efficient in LSB detection.

Keywords: multiple mirror telescopes; astronomy data reduction; galaxies
The Case for an Early Solar Binary Companion

We show that an equal-mass, temporary binary companion to the Sun in the solar birth cluster at a separation of ∼103 au would have increased the likelihood of forming the observed population of outer Oort Cloud objects and of capturing Planet Nine. In particular, the discovery of a captured origin for Planet Nine would favor our binary model by an order of magnitude relative to a lone stellar history. Our model predicts an overabundance of dwarf planets, discoverable by Legacy Survey of Space and Time, with similar orbits to Planet Nine, which would result from capture by the stellar binary.

Keywords: binary stars; oort cloud
Quasi-periodic Pulsations of Gamma-Ray Emissions from a Solar Flare on 2017 September 6

We investigate quasi-periodic pulsations (QPPs) of high-energy nonthermal emissions from an X9.3 flare (SOL2017-Sep-06T11:53), the most powerful flare since the beginning of solar cycle 24. The QPPs are identified as a series of regular and repeating peaks in the light curves in the γ- and hard X-ray (HXR) channels recorded by the Konus-Wind, as well as the radio and microwave fluxes measured by the CALLISTO radio spectrograph during the impulsive phase. The periods are determined from the global wavelet and Fourier power spectra as 24-30 s in the HXR and microwave channels, which are associated with nonthermal electrons, and ∼20 s in the γ-ray band related to nonthermal ions. Both nonthermal electrons and ions may be accelerated by repetitive magnetic reconnection during the impulsive phase. However, we could not rule out other mechanisms, such as magnetohydrodynamic oscillation in a sausage mode. The QPP detected in this study is useful for understanding the particle acceleration and dynamic process in solar flares and also bridging the gap between stellar and solar flares because the energy realm of the X9.3 solar flare is almost comparable to a typical stellar flare.

Keywords: solar x-ray emission; solar gamma-ray emission; solar oscillations; solar flares; solar radio emission
Revising Properties of Planet-Host Binary Systems. II. Apparent Near-Earth-analog Planets in Binaries Are Often Sub-Neptunes

Identifying rocky planets in or near the habitable zones of their stars (near-Earth analogs) is one of the key motivations of many past and present planet-search missions. The census of near-Earth analogs is important because it informs calculations of the occurrence rate of Earth-like planets, which in turn feed into calculations of the yield of future missions to directly image other Earths. Only a small number of potential near-Earth analogs have been identified, meaning that each planet should be vetted carefully and then incorporated into the occurrence rate calculation. A number of putative near-Earth analogs have been identified within binary-star systems. However, stellar multiplicity can bias measured planetary properties, meaning that apparent near-Earth analogs in close binaries may have different radii or instellations than initially measured. We simultaneously fit unresolved optical spectroscopy, optical speckle and near-IR adaptive optics contrasts, and unresolved photometry and retrieved revised stellar temperatures and radii for a sample of 11 binary Kepler targets that host at least one near-Earth-analog planet, for a total of 17 planet candidates. We found that 10 of the 17 planets in our sample had radii that fell in or above the radius gap, suggesting that they are not rocky planets. Only two planets retained super-Earth radii and stayed in the habitable zone, making them good candidates for inclusion in rocky-planet occurrence rate calculations. *Based on observations obtained with the Hobby-Eberly Telescope, which is a joint project of the University of Texas at Austin, the Pennsylvania State University, Ludwig-Maximilians-Universität München, and Georg-August-Universität Göttingen.

Keywords: exoplanets; super earths; main sequence stars; binary stars; visual binary stars
Power-law Pseudo-phase-space Density Profiles of Dark Matter Halos: A Fluke of Physics?

It has been known for nearly 20 yr that the pseudo-phase-space density profile of equilibrium simulated dark matter halos, ρ(r)/σ3(r), is well described by a power law over three decades in radius, even though both the density ρ(r) and the velocity dispersion σ(r) deviate significantly from power laws. The origin of this scale-free behavior is not understood. It could be an inherent property of self-gravitating collisionless systems, or it could be a mere coincidence. To address the question we work with equilibrium halos and, more specifically, the second derivative of the Jeans equation, which, under the assumptions of (I) the Einasto density profile, (II) the linear velocity anisotropy-density slope relation, and (III) ρ/σ3 ∝ r-α, can be transformed from a differential equation to a cubic algebraic equation. Relations (I)-(III) are all observed in numerical simulations and are well parameterized by a total of four or six model parameters. We do not consider the dynamical evolution of halos; instead, taking advantage of the fact that the algebraic Jeans equation for equilibrium halos puts relations (I)-(III) on the same footing, we study the (approximate) solutions of this equation in the four- and six-dimensional spaces. We argue that the distribution of best solutions in these parameter spaces is inconsistent with ρ/σ3 ∝ r-α being a fundamental property of gravitational evolution and conclude that the scale-free nature of this quantity is likely to be a fluke.

Keywords: dark matter; cosmology; dark matter density
Breakdown of the Newton-Einstein Standard Gravity at Low Acceleration in Internal Dynamics of Wide Binary Stars

A gravitational anomaly is found at weak gravitational acceleration g N ≲ 10-9 m s-2 from analyses of the dynamics of wide binary stars selected from the Gaia DR3 database that have accurate distances, proper motions, and reliably inferred stellar masses. Implicit high-order multiplicities are required and the multiplicity fraction is calibrated so that binary internal motions agree statistically with Newtonian dynamics at a high enough acceleration of ≈10-8 m s-2. The observed sky-projected motions and separation are deprojected to the 3D relative velocity v and separation r through a Monte Carlo method, and a statistical relation between the Newtonian acceleration g N ≡ GM/r 2 (where M is the total mass of the binary system) and a kinematic acceleration g ≡ v 2/r is compared with the corresponding relation predicted by Newtonian dynamics. The empirical acceleration relation at ≲10-9 m s-2 systematically deviates from the Newtonian expectation. A gravitational anomaly parameter δ obs-newt between the observed acceleration at g N and the Newtonian prediction is measured to be: δ obs-newt = 0.034 ± 0.007 and 0.109 ± 0.013 at g N ≈ 10-8.91 and 10-10.15 m s-2, from the main sample of 26,615 wide binaries within 200 pc. These two deviations in the same direction represent a 10σ significance. The deviation represents a direct evidence for the breakdown of standard gravity at weak acceleration. At g N = 10-10.15 m s-2, the observed to Newton-predicted acceleration ratio is ${g}_{\mathrm{obs}}/{g}_{\mathrm{pred}}={10}^{\sqrt{2}{\delta }_{\mathrm{obs}-\mathrm{newt}}}=1.43\pm 0.06$ . This systematic deviation agrees with the boost factor that the AQUAL theory predicts for kinematic accelerations in circular orbits under the Galactic external field.

Keywords: binary stars; gravitation; modified newtonian dynamics; non-standard theories of gravity
Realistic Dispersion of Plasmaspheric Hiss in the Inner Magnetosphere and Its Effect on Wave-induced Electron Scattering Rates

The cold plasma approximation is a common treatment to study wave-particle interactions between plasmaspheric hiss and magnetospheric electrons, which, however, can become a challenge during periods of disturbed geomagnetic activity. To assess the validity of the cold plasma dispersion relation of plasmaspheric hiss, we adopt the cold plasma theory to calculate the wave magnetic field intensities from the electric field intensities observed by Van Allen Probe A from 2012 October 1 to 2018 February 28. Comparisons between the observed and converted hiss magnetic field intensities capture pronounced differences with the enhancement of substorm activity, and exhibit the largest discrepancies on the nightside MLT sector for low-frequency hiss waves. We also use both the hiss dispersion curves derived from the observations and the cold plasma dispersion relation to evaluate hiss-induced electron diffusion coefficients under different substorm activity conditions. The results indicate that the profiles of electron diffusion rates vary considerably for the two hiss dispersion relations and that the differences between them become increasingly distinct with substorm activity intensification. Our study therefore demonstrates that the cold plasma theory can become less reliable for plasmaspheric hiss waves under disturbed geomagnetic circumstances and that the realistic wave dispersion is essential to better quantify the electron scattering effect of hiss waves, which needs to be carefully incorporated into future global simulations of the generation and propagation of plasmaspheric hiss and associated dynamic variability of radiation belt electrons.

Keywords: van allen radiation belts; planetary magnetospheres
Evidence for Large-scale Excesses Associated with Low H I Column Densities in the Sky. I. Dust Excess

Where dust and gas are uniformly mixed, atomic hydrogen can be traced through the detection of far-infrared (FIR) or UV emission of dust. We considered, for the origin of discrepancies observed between various direct and indirect tracers of gas outside the Galactic plane, possible corrections to the zero levels of the Planck High Frequency Instrument (HFI) detectors. We set the zero levels of the Planck-HFI skymaps as well as the 100 μm map from COBE/DIRBE and IRAS from the correlation between FIR emission and atomic hydrogen column density excluding regions of lowest gas column density. A modified blackbody model fit to those new zero-subtracted maps led to significantly different maps of the opacity spectral index β and temperature T and an overall increase in the optical depth at 353 GHz τ 353 of 7.1 × 10-7 compared to the data release 2 Planck map. When comparing τ 353 and the H I column density, we observed a uniform spatial distribution of the opacity outside regions with dark neutral gas and CO except in various large-scale regions of low N H I that represent 25% of the sky. In those regions, we observed an average dust column density 45% higher than predictions based on N H I with a maximum of 250% toward the Lockman Hole region. From the average opacity σ e353 = (8.9 ± 0.1) × 10-27 cm2, we deduced a dust-to-gas mass ratio of 0.53 × 10-2. We did not see evidence of dust associated with a Reynolds layer of ionized hydrogen. We measured a far-ultraviolet isotropic intensity of 137 ± 15 photons s-1 cm-2 sr-1 Å-1 in agreement with extragalactic flux predictions and a near-ultraviolet isotropic intensity of 378 ± 45 photons s-1 cm-2 sr-1 Å-1 corresponding to twice the predicted flux.

Keywords: interstellar medium; interstellar thermal emission; dust continuum emission; far infrared astronomy; ultraviolet surveys
Image Deconvolution and Point-spread Function Reconstruction with STARRED: A Wavelet-based Two-channel Method Optimized for Light-curve Extraction

We present STARRED, a point-spread function (PSF) reconstruction, two-channel deconvolution, and light-curve extraction method designed for high-precision photometric measurements in imaging time series. An improved resolution of the data is targeted rather than an infinite one, thereby minimizing deconvolution artifacts. In addition, STARRED performs a joint deconvolution of all available data, accounting for epoch-to-epoch variations of the PSF and decomposing the resulting deconvolved image into a point source and an extended source channel. The output is a high-signal-to-noise-ratio, high-resolution frame combining all data and the photometry of all point sources in the field of view as a function of time. Of note, STARRED also provides exquisite PSF models for each data frame. We showcase three applications of STARRED in the context of the imminent LSST survey and of JWST imaging: (i) the extraction of supernovae light curves and the scene representation of their host galaxy; (ii) the extraction of lensed quasar light curves for time-delay cosmography; and (iii) the measurement of the spectral energy distribution of globular clusters in the "Sparkler," a galaxy at redshift z = 1.378 strongly lensed by the galaxy cluster SMACS J0723.3-7327. STARRED is implemented in JAX, leveraging automatic differentiation and graphics processing unit acceleration. This enables the rapid processing of large time-domain data sets, positioning the method as a powerful tool for extracting light curves from the multitude of lensed or unlensed variable and transient objects in the Rubin-LSST data, even when blended with intervening objects.

Keywords: deconvolution; photometry; light curves; astronomy image processing
A Comparison of Global Magnetofrictional Simulations of the 2015 March 20 Solar Eclipse

The solar corona exhibits a wide range of phenomena, from highly non-potential objects such as solar filaments to near-potential structures such as the open magnetic flux. For any global model to be useful in space weather applications, the model must on a single day reproduce all of these phenomena in the same simulation, using the same set of coronal physics and parameters. The purpose of the present paper is to evaluate whether the evolving magnetofrictional model can achieve this goal. Twenty-eight separate simulations are analyzed, where each tries to reproduce both highly non-potential and near-potential phenomena observed in the solar corona on the same day. This day is chosen to be 2015 March 20, the date of the solar eclipse. The study evaluates how the cadence of bipole data, ideal or nonideal coronal physics, and the variety of helicity injection mechanisms affect the accuracy of the simulations. Results show that significantly better agreement arises when using Advective Flux Transport (AFT) synoptic maps to drive the simulations, as compared to 27-day Carrington rotation synoptic maps. Using the nonideal effect of hyperdiffusion leads to the worst agreement with all coronal phenomena. Alternatively, when running either ideal or ohmic diffusion simulations with helicity condensation or bipoles with a self-helicity, a good agreement with both on-disk and limb structures can be found. This suggests that future studies aiming to simulate the corona and reproduce multiple phenomena on a given day should use data products such as AFT and avoid using the nonideal physics of hyperdiffusion.

Keywords: solar corona; solar magnetic fields; solar evolution; solar prominences
Spectroscopic and Asteroseismic Analysis of the Secondary Clump Red Giant HD 226808

In order to clarify the properties of the secondary clump star HD 226808 (KIC 5307747), we combined four years of data from Kepler space photometry with high-resolution spectroscopy of the High Efficiency and Resolution Mercator Échelle Spectrograph mounted on the Mercator telescope. The fundamental atmospheric parameters, radial velocities, rotation velocities, and elemental abundance for Fe and Li were determined by analyzing line strengths and fitting-line profiles, based on a 1D local thermodynamic equilibrium model atmosphere. Second, we analyzed a photometric light curve obtained by Kepler and we extracted asteroseismic data of this target using Lets Analysis, Use and Report of Asteroseismology, a new seismic tool developed for the study of evolved FGK solar-like stars. We determined the evolutionary status and effective temperature, surface gravity, metallicity, microturbulence, and chemical abundances for Li, Ti, Fe, and Ni for HD 226808, by employing spectroscopy, asteroseismic scaling relations, and evolutionary structure models built in order to match observed data. Our results also show that an accurate synergy between good spectroscopic analysis and asteroseismology can provide a jump toward understanding evolved stars.

Keywords: stellar abundances; high resolution spectroscopy; red giant clump; asteroseismology
Discovery of Astrometric Accelerations by Dark Companions in the Globular Cluster ω Centauri

We present results from the search for astrometric accelerations of stars in ω Centauri using 13 yr of regularly scheduled Hubble Space Telescope WFC3/UVIS calibration observations in the cluster core. The high-precision astrometry of ∼160,000 sources was searched for significant deviations from linear proper motion. This led to the discovery of four cluster members and one foreground field star with compelling acceleration patterns. We interpreted them as the result of the gravitational pull by an invisible companion and determined preliminary Keplerian orbit parameters, including the companion's mass. For the cluster members, our analysis suggests periods ranging from 8.8 to 19+ yr and dark companions in the mass range of ∼0.7 to ∼1.4M ☉. At least one companion could exceed the upper mass boundary of white dwarfs and can be classified as a neutron star candidate.

Keywords: astrometry; globular star clusters; hubble space telescope; hst photometry; binary stars; white dwarf stars; neutron stars; black holes; gaia; space observatories; keplerian orbit
Confined and Eruptive Catastrophes of Solar Magnetic Flux Ropes Caused by Mass Loading and Unloading

It is widely accepted that coronal magnetic flux ropes are the core structures of large-scale solar eruptive activities, which have a dramatic impact on the solar-terrestrial system. Previous studies have demonstrated that varying magnetic properties of a coronal flux rope system could result in a catastrophe of the rope, which may trigger solar eruptive activities. Since the total mass of a flux rope also plays an important role in stabilizing the rope, we use 2.5 dimensional magnetohydrodynamic numerical simulations in this article to investigate how a flux rope evolves as its total mass varies. It is found that an unloading process that decreases the total mass of the rope could result in an upward (eruptive) catastrophe in the flux rope system, during which the rope jumps upward and the magnetic energy is released. This indicates that mass unloading processes could initiate the eruption of the flux rope. Moreover, when the system is not too diffusive, there is also a downward (confined) catastrophe that could be caused by mass loading processes via which the total mass accumulates. The magnetic energy, however, is increased during the downward catastrophe, indicating that mass loading processes could cause confined activities that may contribute to the storage of energy before the onset of coronal eruptions.

Keywords: solar prominences; solar flares; solar filament eruptions; solar coronal mass ejections; solar filaments; solar activity; quiescent solar prominence
Chemical Compositions of Red Giant Stars from Habitable Zone Planet Finder Spectroscopy

We have used the Habitable Zone Planet Finder (HPF) to gather high-resolution, high signal-to-noise near-infrared spectra of 13 field red horizontal branch (RHB) stars, one open cluster giant, and one very metal-poor halo red giant. The HPF spectra cover the 0.81-1.28 μm wavelength range of the zyJ bands, partially filling the gap between the optical (0.4-1.0 μm) and infrared (1.5-2.4 μm) spectra already available for the program stars. We derive abundances of 17 species from LTE-based computations involving equivalent widths and spectrum syntheses, and estimate abundance corrections for the species that are most affected by departures from LTE in RHB stars. Generally good agreement is found between HPF-based metallicities and abundance ratios and those from the optical and infrared spectral regions. Light element transitions dominate the HPF spectra of these red giants, and HPF data can be used to derive abundances from species with poor or no representation in optical spectra (e.g., C I, P I, S I, K I). Attention is drawn to the HPF abundances in two field solar-metallicity RHB stars of special interest: one with an extreme carbon isotope ratio, and one with a rare, very large lithium content. The latter star is unique in our sample in exhibiting very strong He I 10830 Å absorption. The abundances of the open cluster giant concur with those derived from other wavelength regions. Detections of C I and S I in HD 122563 are reported, yielding the lowest metallicity determination of [S/Fe] from more than one multiplet.

Keywords: chemical abundances; metallicity; near infrared astronomy; atomic spectroscopy; horizontal branch
Analyses of Johannes Kepler's Sunspot Drawings in 1607: A Revised Scenario for the Solar Cycles in the Early 17th Century

Telescopic sunspot observations began in 1610 and captured subsequent solar cycles. In combination with proxy reconstructions on an annual scale, these data sets indicate a gradual transition between regular solar cycles and the Maunder Minimum. The telescopic sunspot observations missed the beginning of the first telescopic solar cycle (Solar Cycle ‑13), leaving room for considerable uncertainty as to its temporal evolution. Before these early telescopic observations, however, Kepler made solar observations using camerae obscurae and recorded a sunspot group in three solar drawings in 1607. Here, we make use of Kepler's sunspot drawings and descriptive texts to identify his observational sites and time stamps. We have deprojected his sunspot drawings and compared the reported positions with our calculations of the inclination of the solar equator as seen from these sites at that time. These results locate the reported sunspot group near the solar equator eastward from the central meridian. This contrasts with telescopic sunspot drawings from the 1610s that show sunspot groups in the higher heliographic latitudes. Therefore, what Kepler saw was probably a sunspot group from Solar Cycle ‑14, rather than one from Solar Cycle ‑13. These records allow us to place the beginning of Solar Cycle ‑13 between 1607 and 1610. In comparison with the 14C-based solar-cycle reconstructions, our result supports regular solar-cycle durations around the 1610s, rather than any suggested extreme extensions of the solar-cycle duration(s) around the 1610s.

Keywords: sunspot groups; sunspot cycle; sunspots; solar cycle; maunder minimum; solar-terrestrial interactions