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3D Magnetic Free Energy and Flaring Activity Using 83 Major Solar Flares

In this Letter, we examine the relationship between 3D magnetic free energy (MFE) and flaring activity using 83 major solar flares (M-class and X-class) in nine solar active regions (ARs). For this, we use 998 nonlinear force-free field extrapolations compiled by the "Institute for Space-Earth Environmental Research Database" at Nagoya University. These ARs produced at least three major flares with distinct rising and peak phases of 3D MFE. For each phase, the solar flare occurrence rate (FOR) is calculated as a ratio of the number of flares to the duration. The major results from this study are summarized as follows. First, there is no clear linear correlation (CC = 0.15) between 3D MFE and flare peak flux. Second, the FOR (3.4 day‑1) of the rising phase is a little higher than that (3.1 day‑1) of the peak phase, depending on AR. Third, for several flares, there are noticeable decreases in 3D MFE, which correspond to the typical energy of a major flare (about 1032 erg). Fourth, it is interesting to note that there are noticeable enhancements in FORs at several local maxima of 3D MFE, which may be associated with flux emergence and/or shearing motions. Fifth, the flare index rates, which are defined as the summation of flaring activity divided by the duration, of rising and peak phases are 151 day‑1 and 314 day‑1, respectively. Our results imply that the traditional and simple "storage and release" model does not apply to flare activities, and the random perturbation may be important for triggering flares.

Keywords: solar flares; solar active regions; solar magnetic fields; the sun; solar magnetic flux emergence
The Art of Modeling Stellar Mergers and the Case of the B[e] Supergiant R4 in the Small Magellanic Cloud

Most massive stars exchange mass with a companion, leading to evolution which is altered drastically from that expected of stars in isolation. Such systems result from unusual binary evolution pathways and can place stringent constraints on the physics of these interactions. We use the R4 binary system's B[e] supergiant, which has been postulated to be the product of a stellar merger, to guide our understanding of such outcomes by comparing observations of R4 to the results of simulating a merger with the 3D hydrodynamics code FLASH. Our approach tailors the simulation initial conditions to observed properties of R4 and implements realistic stellar profiles from the 1D stellar evolution code MESA onto the 3D grid, resolving the merger inspiral to within 0.02 R⊙. We map the merger remnant into MESA to track its evolution on the H-R diagram over a period of 104 yr. This generates a model for a B[e] supergiant with stellar properties, age, and nebula structure in qualitative agreement with those of the R4 system. Our calculations provide evidence to support the idea that R4's B[e] supergiant was originally a member of a triple system in which the inner binary merged after its most massive member evolved off the main sequence, producing a new object of similar mass but significantly more luminosity than the A supergiant companion. The code framework presented in this paper, which was constructed to model tidal encounters, can be used to generate accurate models of a wide variety of merger stellar remnants.

Keywords: binary stars; stellar mergers; hydrodynamical simulations
Differencing and Coadding JWST Images with Matched Point-spread Function

We present an algorithm to derive difference images for data taken with JWST with matched point-spread functions (PSFs). It is based on the saccadic fast Fourier transform method but with revisions to accommodate the rotations and spatial variations of the PSFs. It allows for spatially varying kernels in B-spline form with separately controlled photometric scaling and Tikhonov kernel regularization for harnessing the ultimate fitting flexibility. We present this method using the JWST/NIRCam images of galaxy cluster Abell 2744 acquired in JWST Cycle 1 as the test data. The algorithm can be useful for time-domain source detection and differential photometry with JWST. It can also coadd images of multiple exposures taken at different field orientations. The coadded images preserve the sharpness of the central cores of the PSFs, and the positions and shapes of the objects are matched precisely with B-splines across the field.

Keywords: astronomy software; transient detection
Stellar Superflares Observed Simultaneously with Kepler and XMM-Newton

Solar and stellar flares are powerful events that produce intense radiation across the electromagnetic spectrum. Multiwavelength observations are highly important for understanding the nature of flares, because different flare-related processes reveal themselves in different spectral ranges. To study the correlation between thermal and nonthermal processes in stellar flares, we have searched the databases of Kepler (optical observations) and XMM-Newton (soft X-rays) for the flares observed simultaneously with both instruments; nine distinctive flares (with energies exceeding 1033 erg) on three stars (of K-M spectral classes) have been found. We have analyzed and compared the flare parameters in the optical and X-ray spectral ranges; we have also compared the obtained results with similar observations of solar flares. Most of the studied stellar flares released more energy in the optical range than in X-rays. In one flare, X-ray emission strongly dominated, which could be caused either by a soft spectrum of energetic electrons or by a near-limb position of this flare. The X-ray flares were typically delayed with respect to and shorter than their optical counterparts, which is partially consistent with the Neupert effect. Using the scaling laws based on the magnetic reconnection theory, we have estimated the characteristic magnetic field strengths in the stellar active regions and the sizes of these active regions as about 25-70 G and 250,000-500,000 km, respectively. The observed stellar superflares appear to be scaled-up versions of solar flares, with a similar underlying mechanism and nearly the same characteristic magnetic field values, but with much larger active region sizes.

Keywords: optical flares; stellar x-ray flares; markov chain monte carlo
Groups and Protocluster Candidates in the CLAUDS and HSC-SSP Joint Deep Surveys

Using the extended halo-based group finder developed by Yang et al., which is able to deal with galaxies via spectroscopic and photometric redshifts simultaneously, we construct galaxy group and candidate protocluster catalogs in a wide redshift range (0 < z < 6) from the joint CFHT Large Area U-band Deep Survey and Hyper Suprime-Cam Subaru Strategic Program deep data set. Based on a selection of 5,607,052 galaxies with i-band magnitude m i < 26 and a sky coverage of 34.41 deg2, we identify a total of 2,232,134 groups, of which 402,947 groups have at least three member galaxies. We have visually checked and discussed the general properties of these richest groups at redshift z > 2.0. By checking the galaxy number distributions within a 5-7 h -1Mpc projected separation and a redshift difference Δz ≤ 0.1 around those richest groups at redshift z > 2, we identify lists of 761, 343, and 43 protocluster candidates in the redshift bins 2 ≤ z < 3, 3 ≤ z < 4, and z ≥ 4, respectively. In general, these catalogs of galaxy groups and protocluster candidates will provide useful environmental information in probing galaxy evolution along cosmic time.

Keywords: dark matter; dark matter distribution; large-scale structure of the universe; galaxies; galaxy groups; galaxy clusters; galaxy dark matter halos; protoclusters; galaxy evolution
HST UV Observations of Asteroid (16) Psyche

The Main Belt Asteroid (16) Psyche is the target object of the NASA Discovery Mission Psyche. We observed the asteroid at ultraviolet (UV) wavelengths (170-310 nm) using the Space Telescope Imaging Spectrograph on the Hubble Space Telescope during two separate observations. We report that the spectrum is very red in the UV, with a blue upturn shortward of ∼200 nm. We find an absorption feature at 250 nm and a weaker absorption feature at 275 nm that may be attributed to a metal-oxide charge transfer band. We find that the red-sloped, relatively featureless spectrum of (16) Psyche is best matched with the reflectance spectrum of pure iron; however, our intimate mixture models show that small grains of iron may dominate the reflectance spectrum even if iron only comprises up to 10% of the material on the surface. We also stress that there is a limited database of reflectances for planetary surface analogs at UV wavelengths for comparison with the spectrum of (16) Psyche. The mid- and far-UV spectra (<240 nm) are markedly different for each of the four asteroids observed at these wavelengths so far, including ones in the same spectral class, indicating that UV observations of asteroids could be used to better understand differences in the composition and processing of the surfaces of these small bodies.

Keywords: main belt asteroids; ultraviolet astronomy; hubble space telescope
Magnetic Fields and Plasma Heating in the Sun's Atmosphere

We use the first publicly available data from the Daniel K. Inouye Solar Telescope to track magnetic connections from the solar photosphere into the corona. We scrutinize relationships between chromospheric magnetism and bright chromospheric, transition region, and coronal plasmas. In 2022 June, the Visible Spectro-Polarimeter (ViSP) instrument targeted unipolar network within a decaying active region. ViSP acquired rastered scans with longitudinal Zeeman sensitivities of 0.25 Mx cm-2 (Fe I, 630.2 nm) and 0.5 Mx cm-2 (Ca II, 854.2 nm). ViSP was operated in a "low" resolution mode (0.″214 slit width, spectral resolution ${ \mathcal R }\approx {\rm{70,000}}$ ) to produce polarization maps over a common area of 105″ × 50″. Data from the Solar Dynamics Observatory and Interface Region Imaging Spectrograph are combined to ask: Why is only a fraction of emerging flux filled with heated plasma? What is the elemental nature of the plasmas? No correlations were found between heated plasma and the properties of chromospheric magnetic fields derived from the weak field approximation, on scales below supergranules. Processes hidden from our observations control plasma heating. While improved magnetic measurements are needed, these data indicate that "the corona is a self-regulating forced system." Heating depends on the state of the corona, not simply on boundary conditions. Heating models based upon identifiable bipolar fields, including cool loops, tectonics, and observable magnetic reconnection, are refuted for these regions with unipolar chromospheric magnetic fields.

Keywords: solar coronal heating; solar chromospheric heating; solar magnetic fields; magnetohydrodynamics
The Most Sensitive SETI Observations Toward Barnard's Star with FAST

Search for extraterrestrial intelligence (SETI) has been mainly focused on nearby stars and their planets in recent years. Barnard's star is the second closest star system to the Sun and the closest star in the Five-hundred-meter Aperture Spherical radio Telescope (FAST) observable sky which makes the minimum Equivalent Isotropic Radiated Power required for a hypothetical radio transmitter from Barnard's star to be detected by FAST telescope a mere 4.36 × 108 W. In this paper, we present the FAST telescope as the most sensitive instrument for radio SETI observations toward nearby star systems and conduct a series of observations to Barnard's star (GJ 699). By applying the multibeam coincidence matching strategy on the FAST telescope, we search for narrow-band signals (~Hz) in the frequency range of 1.05-1.45 GHz, and two orthogonal linear polarization directions are recorded. Despite finding no evidence of radio technosignatures in our series of observations, we have developed predictions regarding the hypothetical extraterrestrial intelligence signal originating from Barnard's star. These predictions are based on the star's physical properties and our observation strategy.

Keywords: astrobiology; search for extraterrestrial intelligence; technosignatures; exoplanets
The Roles of Dust Growth in the Temperature Evolution and Snow Line Migration in Magnetically Accreting Protoplanetary Disks

The temperature structure of protoplanetary disks provides an important constraint on where in the disks rocky planets like our own form. Recent nonideal magnetohydrodynamical (MHD) simulations have shown that the internal Joule heating associated with magnetically driven disk accretion is inefficient at heating the disk midplane. A disk temperature model based on the MHD simulations predicts that in a disk around a solar-mass young star, the water snow line can move inside the current Earth's orbit within 1 Myr after disk formation. However, the efficiency of the internal Joule heating depends on the disk's ionization and opacity structures, both of which are governed by dust grains. In this study, we investigate these effects by combining the previous temperature model for magnetically accreting disks with a parameterized model for the grain size and vertical distribution. Grain growth enhances the gas ionization fraction and thereby allows Joule heating to occur closer to the midplane. However, growth beyond 10 μm causes a decrease in the disk opacity, leading to a lower midplane temperature. The combination of these two effects results in the midplane temperature being maximized when the grain size is in the range 10-100 μm. Grain growth to millimeter sizes can also delay the snow line's migration to the 1 au orbit by up to a few million years. We conclude that accounting for dust growth is essential for accurately modeling the snow line evolution and terrestrial planet formation in magnetically accreting protoplanetary disks.

Keywords: protoplanetary disks; magnetohydrodynamics; planet formation; solar system terrestrial planets
High-resolution Spectroscopic Metallicities of Milky Way Cepheid Standards and Their Impact on the Leavitt Law and the Hubble Constant

Milky Way Cepheid variables with accurate Hubble Space Telescope photometry have been established as standards for primary calibration of the cosmic distance ladder to achieve a percent-level determination of the Hubble constant (H 0). These 75 Cepheid standards are the fundamental sample for investigation of possible residual systematics in the local H 0 determination due to metallicity effects on their period-luminosity relations. We obtained new high-resolution (R ~ 81,000), high-signal-to-noise (S/N ~ 50-150) multiepoch spectra of 42 out of 75 Cepheid standards using the ESPaDOnS instrument at the 3.6 m Canada-France-Hawaii Telescope. Our spectroscopic metallicity measurements are in good agreement with the literature values with systematic differences up to 0.1 dex due to different metallicity scales. We homogenized and updated the spectroscopic metallicities of all 75 Milky Way Cepheid standards and derived their multiwavelength (GVIJHK s ) period-luminosity-metallicity and period-Wesenheit-metallicity relations using the latest Gaia parallaxes. The metallicity coefficients of these empirically calibrated relations exhibit large uncertainties due to low statistics and a narrow metallicity range (Δ[Fe/H] = 0.6 dex). These metallicity coefficients are up to 3 times better constrained if we include Cepheids in the Large Magellanic Cloud and range between -0.21 ± 0.07 and -0.43 ± 0.06 mag dex-1. The updated spectroscopic metallicities of these Milky Way Cepheid standards were used in the Cepheid-supernovae distance ladder formalism to determine H 0 = 72.9 ± 1.0 km s-1 Mpc-1, suggesting little variation (~0.1 km s-1 Mpc-1) in the local H 0 measurements due to different Cepheid metallicity scales.

Keywords: distance indicators; stellar pulsations; hubble constant; cepheid variable stars
The Merger Rate of Primordial Black Hole-Neutron Star Binaries in Ellipsoidal-collapse Dark Matter Halo Models

In this work, we calculate the merger rate of primordial black hole-neutron star (PBH-NS) binaries within the framework of ellipsoidal-collapse dark matter models and compare it with that obtained from spherical-collapse dark matter halo models. Our results exhibit that ellipsoidal-collapse dark matter halo models can potentially amplify the merger rate of PBH-NS binaries in such a way that it is very close to the range estimated by the LIGO-Virgo observations. In contrast, spherical-collapse dark matter halo models cannot justify PBH-NS merger events as consistent results with the latest gravitational wave data reported by the LIGO-Virgo collaborations. In addition, we calculate the merger rate of PBH-NS binaries as a function of PBH mass and fraction within the context of ellipsoidal-collapse dark matter halo models. The results indicate that PBH-NS merger events with masses of M PBH ≤ 5M ⊙, M NS ≃ 1.4M ⊙ will be consistent with the LIGO-Virgo observations if f PBH ≃ 1.

Keywords: dark matter; primordial black holes; neutron stars; gravitational collapse; compact objects
Super-Earth GJ 667Cc: Age and XUV Irradiances of the Temperate-zone Planet with Potential for Advanced Life

GJ 667Cc is a nearby (23.6 lt-yr) super-Earth that orbits within the habitable zone (HZ) of its ~M2V host star and has Earth-like properties: (M- $\sin (i)\sim 4.1\,{M}_{\oplus };$ R ~ 1.7 R ⊕; T eq (A = 0.3) ~ 277 K). The age of the star/planet is poorly constrained at 2 ≳ Gyr. Age is crucial in evaluating the potential for complex life. We determine an age of ~6.10 ± 2.2 Gyr from our recent Age-Rotation relations. This is compatible with its low metallicity ([Fe/H] ~ -0.59 ± 0.1 dex), weak coronal/chromospheric X-ray/FUV emissions, and space motions. We also determine the photodissociating/photoionizing X-ray-UV irradiances from Chandra and ROSAT X-ray and HST/FUV observations. Like most HZ-planets hosted by M-dwarfs, these irradiances are much higher than Earth's and are detrimental to the planet's atmosphere retention, water inventories, and habitability. A strong geomagnetic field could mitigate atmospheric erosion, permitting life to develop.

Keywords: m dwarf stars; exoplanets; habitable planets; late-type stars; stellar ages; super earths; late-type dwarf stars
KR Persei, a Mid-F Eclipsing Binary with a One-day Period

KR Per is a partially eclipsing binary with an orbital period of 0.9960798 days, very close to one sidereal day, making it difficult to obtain extensive phase coverage in a reasonable amount of time. We used the Wilson-Devinney program to determine its orbital elements and stellar absolute dimensions from recently acquired radial velocities and differential BVRI observations that were supplemented with previous differential UBV measurements and published times of minima. The two components are each F5 V stars with masses of $1.466\pm 0.015\,{M}_{\odot }$ and $1.458\pm 0.015\,{M}_{\odot }$ . The radii are $1.855\pm 0.021\,{R}_{\odot }$ and $1.824\pm 0.022\,{R}_{\odot }$ . The orbital period of the eclipsing system is variable and more times of minima observations are needed. A comparison with evolutionary tracks indicates that the system has an age of 2.1 ± 0.1 Gyr.

Keywords: detached binary stars; eclipsing binary stars; spectroscopic binary stars; fundamental parameters of stars
Measurements of the Hyperfine Structure of Atomic Energy Levels in Co II

Analysis of hyperfine structure constants of singly ionized cobalt (Co II) were performed on cobalt spectra measured by Fourier transform spectrometers in the region 3000-63,000 cm-1 (33333 - 1587 Å). Fits to over 700 spectral lines led to measurements of 292 magnetic dipole hyperfine interaction A constants, with values between -32.5 mK and 59.5 mK (1 mK = 0.001 cm-1). Uncertainties of 255 A constants were between ±0.4 mK and ±3.0 mK, the remaining 37 ranged up to ±7 mK. The electric quadrupole hyperfine interaction B constant could be estimated for only one energy level. The number of Co II levels with known A values has now increased tenfold, improving and enabling the wider, more reliable, and accurate application of Co II in astronomical chemical abundance analyses.

Keywords: atomic physics; atomic spectroscopy; laboratory astrophysics; experimental techniques; line intensities; line positions; spectroscopy
The Diffuse X-Ray Background of the Insight-HXMT/LE Telescope in the Galactic Plane

Accurately estimating of diffuse X-ray background (DXB) is essential for the investigation of sources in the Galactic plane observed with Insight-HXMT/LE, which is a collimated telescope in the soft X-ray energy band with a relatively large field of view. In the high-Galactic-latitude region, DXB is dominated by the cosmic X-ray background, which is almost uniform, but DXB in the Galactic plane region is more complex due to the Galactic H I absorption and the contribution of the Galactic ridge X-ray emission. This study, as a part of background estimation of LE, focuses on estimating the contribution of DXB in the Galactic plane to Insight-HXMT/LE observations. We calculate DXB confined in a region of 0° < l < 360° and ∣b∣ < 10°, where l and b denote Galactic longitude and latitude, respectively, with the first 3 yr of Galactic-plane-scanning survey data of Insight-HXMT/LE. The Galactic plane is divided into 360 × 20 small pixels (1° × 1° per pixel), and a DXB spectrum is obtained for each pixel. An indirect method is developed for the pixels of the bright source regions, which brings a systematic error of ~10%. The systematic error brought by the satellite attitude is ~7% on average for all the pixels in the Galactic plane. The LE DXB spectrum obtained in this study is consistent with that reported by RXTE's Proportional Counter Array.

Keywords: telescopes; astronomy data analysis; x-ray detectors; milky way disk; diffuse x-ray background
VERTICO II: How H I-identified Environmental Mechanisms Affect the Molecular Gas in Cluster Galaxies

In this VERTICO early science paper we explore in detail how environmental mechanisms, identified in H I, affect the resolved properties of molecular gas reservoirs in cluster galaxies. The molecular gas is probed using ALMA ACA (+TP) observations of 12CO(2-1) in 51 spiral galaxies in the Virgo cluster (of which 49 are detected), all of which are included in the VIVA H I survey. The sample spans a stellar mass range of $9\leqslant \mathrm{log}\,{M}_{\star }/{M}_{\odot }\leqslant 11$ . We study molecular gas radial profiles, isodensity radii, and surface densities as a function of galaxy H I deficiency and morphology. There is a weak correlation between global H I and H2 deficiencies, and resolved properties of molecular gas correlate with H I deficiency: galaxies that have large H I deficiencies have relatively steep and truncated molecular gas radial profiles, which is due to the removal of low-surface-density molecular gas on the outskirts. Therefore, while the environmental mechanisms observed in H I also affect molecular gas reservoirs, there is only a moderate reduction of the total amount of molecular gas.

Keywords: galaxies; virgo cluster; interstellar medium; molecular gas; galaxy clusters; galaxy evolution; galaxy environments