Sazuna/UAT_keywords huggingface dataset:
Unveiling Spatiotemporal Properties of the Quasiperiodic Pulsations in the Balmer Continuum at 3600 Å in an X-class Solar White-light Flare. Quasiperiodic pulsations (QPPs) in the Balmer continuum of solar white-light flares (WLFs) are rarely reported, and accurately pinpointing the spatial source of flaring QPPs remains a significant challenge. We present spatiotemporal characteristics of QPPs of an X2.8 two-ribbon solar WLF (SOL2023-12-14T17:02), which was well observed by the White-light Solar Telescope (WST) on board the Advanced Space-based Solar Observatory, with high-cadence imaging (1–2 s) in the Balmer continuum at 3600 Å. Combined with additional multi-instrument data, we find that the enhancement of the WLF in both Balmer and Paschen continua shows strong spatiotemporal correlation with hard X-ray (HXR) emissions. Notably, the pulses in the WST Balmer continuum exhibited a near-zero time lag with most HXR pulses, whereas soft X-ray and extreme ultraviolet emissions showed a lag of 2–3 s. Interestingly, quasi-harmonic QPPs with periods of ∼11 and ∼20 s were observed in multiple wavelengths in the rising phase of the white-light continuum. Furthermore, we employed Fourier transform to spatially locate the QPPs around 11 and 20 s, revealing that they primarily originated from the east flare ribbon, which exhibited the most substantial continuum enhancement. More interestingly, we find that the west ribbon contributed significantly to the 11 s QPP but had a weaker contribution to the 20 s QPP. Moreover, the occurrence of quasi-harmonic QPPs is temporally coincident with the rapid elongation and separation motions of flare ribbons. Possible mechanisms for the quasi-harmonic QPPs have been discussed. These observations provide valuable insights into QPP modeling for solar and stellar flares.

Keywords: Solar flares, Solar x-ray emission, Solar white-light flares, Solar radiation, Solar oscillations, Solar activity, Astronomical location
From Misaligned Sub-Saturns to Aligned Brown Dwarfs: The Highest M<SUB>p</SUB>/M<SUB>*</SUB> Systems Exhibit Low Obliquities, Even around Hot Stars. We present a pattern emerging from stellar obliquity measurements in single-star systems: planets with high planet-to-star mass ratios (MP/M* ≥ 2 × 10‑3)—such as super-Jupiters, brown dwarf companions, and M dwarfs hosting Jupiter-like planets—tend to be aligned, even around hot stars. This alignment represents a 3.7σ deviation from the obliquity distribution observed in systems with lower mass ratios (MP/M* &lt; 2 × 10‑3), which predominantly include Jupiters and sub-Saturns. The only known outlier system, XO-3, exhibits misalignment confirmed via our newly collected Rossiter–McLaughlin effect measurement (λ =  ). However, the relatively large Gaia renormalized unit weight error of XO-3 suggests that it may harbor an undetected binary companion, potentially contributing to its misalignment. Given that tidal realignment mechanisms are weak for hot stars, the observed alignment in high MP/M* systems is likely primordial rather than resulting from tidal interactions. One possible explanation is that only dynamically isolated planets can continue accreting gas and evolve into super-Jupiters while maintaining their primordial alignment. Conversely, planets formed in compact configurations may be unable to grow beyond the gap-opening mass, for which our work suggests an empirical boundary MP/M* = 2 × 10‑3 identified between aligned high MP/M* systems and misaligned low MP/M* systems, with dynamical instabilities contributing to the diverse spin–orbit misalignments observed in the latter. *After our Letter was submitted, Dr. Adam Kraus informed us that he reanalyzed Keck direct imaging data of XO-3 from 2012, 2013, and 2018 (H. Ngo et al. 2015; M. C. Johnson 2018, private communication) and identified a faint companion with a K-band magnitude of 5.7 at a separation of 0 43, corresponding to an M4–M5 star at ∼90 au. This new result excludes the single previously misaligned system above the Mp/M* = 2 × 10‑3 threshold and increases the significance of our result to 4.1σ.

Keywords: Exoplanet dynamics, Planetary theory, Exoplanets, Exoplanet systems, Exoplanet evolution, Star-planet interactions, Exoplanet formation
The Efficiency of Harmonic Emissions Excited by Energetic Electrons in Coronal Loops. Magnetic reconnection is a key process that drives the energy release in solar flares. This process can occur at multiple locations along the coronal loop. The reconnection generates energetic electrons capable of exciting wave modes and emissions as they propagate through the loop. In this follow-up study, we investigate the influence of the injection site location of these energetic electrons, either at the looptop (LT) or at the leg of the loop around a footpoint (FP), on the excitation of wave modes, especially the second harmonic emissions (X2) in coronal loops. Our simulations reveal that the injection location significantly impacts the spatial distribution and intensity of excited wave modes. When electrons are injected at the LT, electromagnetic X2, and Z-modes dominate along the loop, with minimal excitation of Langmuir waves. Conversely, the present study reveals that injection close to FP leads to a strong Langmuir wave excitation throughout the loop, particularly as electrons ascend toward the LT. We find that X2 and Z-modes are consistently excited at the injection site with different intensities, regardless of the injection location. However, electron injection near the FP scenario creates favorable conditions for significant Langmuir wave generation, potentially leading to plasma emission under specific circumstances. These findings emphasize the importance of electron injection location in determining the properties of the excited and emitted waves in solar coronal loops.

Keywords: Solar activity, Radio bursts, Solar coronal radio emission, Solar corona
Impact of Spectral Resolution on S-index and Its Application to Spectroscopic Surveys. Utilizing the PHOENIX synthetic spectra, we investigated the impact of spectral resolution on the calculation of S-indices. We found that for spectra with a resolution lower than ≈30,000, it is crucial to calibrate S-indices for accurate estimations. This is especially essential for low-resolution spectral observations. We provided calibrations for several ongoing or upcoming spectroscopic surveys such as the LAMOST low-resolution survey, the SEGUE survey, the Sloan Digital Sky Survey-V/BOSS survey, the DESI survey, the Maunakea Spectroscopic Explorer survey, and the MUST survey. Using common targets between the HARPS and Mount Wilson Observatory (MWO) observations, we established conversions from spectral S-indices to the well-known SMWO values, applicable to stars with [Fe/H] values greater than ‑1. These calibrations offer a reliable approach to converting S-indices obtained from various spectroscopic surveys into SMWO values and can be widely applied in studies on chromospheric activity.

Keywords: Late-type stars, Stellar activity
Upper Limits on the Gamma-Ray Emission from the Microquasar V4641 Sgr. Following a recent detection of TeV radiation by the Large High Altitude Air Shower Observatory and the High-Altitude Water Cherenkov Observatory, coincident with the direction of the microquasar V4641 Sgr, we search for possible GeV emission from this source. We explored the morphology and temporal features of the source as well as two nearby unassociated point sources, which could be a part of the extended structure of V4641 Sgr, and compared results with corresponding X-ray and TeV emissions. No significant gamma-ray signal linked to V4641 Sgr was detected in the energy range of 1–300 GeV. The 95% confidence level upper limits for the flux from the source, assuming both point and extended source models, were 5.38 × 10‑13 erg cm‑2 s‑1 and 1.12 × 10‑12 erg cm‑2 s‑1, respectively. Additionally, no correlation between the gamma-ray light curve and X-ray outbursts was observed.

Keywords: Gamma-ray astronomy
The Observations of Magnetic Reconnection during the Interaction Process of Two Active Region Filaments. We investigate the interaction between two filaments (F1 and F2) and their subsequent magnetic reconnection in active region (AR) NOAA 13296 and AR NOAA 13293 on 2023 May 9, utilizing high spatial and temporal resolution and multiwavelength observational data from the Solar Dynamics Observatory, the New Vacuum Solar Telescope, and the Chinese Hα Solar Explorer. The movement of F1 from the southeast toward the northwest, driven by the motion of the positive magnetic polarity (P1), leads to a collision and reconnection with F2. This reconnection exchanges their footpoints, resulting in the formation of two new filaments (F3 and F4) consistent with "slingshot" type filament interaction. During the interaction, the current sheet, moving due to the motion of F1, and the reconnection outflows, moving along F3 and F4, were both observed. The current sheet is rarely observed in the slingshot type filament interaction, measuring approximately 2.17 Mm in length and 0.84 Mm in width. After the interaction, the F1 disappears, whereas a portion of F2 remains, indicating that the interaction involves partial slingshot reconnection, due to the unequal magnetic flux between the filaments. The residual part of F2 will undergo another magnetic reconnection in the same interaction region with the magnetic loops connecting polarities N1 and P1. The material generated by the reconnection is continuously injected into F4, leading to its final morphology. The findings enhance our understanding of slingshot-type filament interactions, indicating that partial slingshot reconnections between filaments may be more common than full slingshot events.

Keywords: The Sun, Solar filaments, Solar magnetic reconnection
Detection of an Orphan X-Ray Flare from a Blazar Candidate EP240709a with the Einstein Probe. Blazars are often observed to flare across multiple wavelengths. Orphan flares from blazars have only been detected a few times, providing an opportunity to understand the structure of the jet in the accreting system. We report a remarkable orphan X-ray flare from a blazar candidate EP240709a, detected by the Einstein Probe (EP) in July 2024. The multiband spectral properties and variability support EP240709a as a high-energy peaked BL Lacertae-type object. The flux in 0.5–10 keV increased by at least 28 times to the value of low state in 2020, with no significant flaring detected in other bands during the same period. EP240709a exhibits the harder-when-brighter tendency in the X-ray band during the orphan flare, while its infrared-optical spectra are featureless. We employ one-zone and two-zone leptonic synchrotron self-Compton models to perform the spectral energy distribution fitting. Detecting this rare orphan flare shows the potential of EP in discovering peculiar activities from AGN in high-cadence X-ray sky surveys.

Keywords: Blazars, Jets, Active galactic nuclei, High energy astrophysics
Energetic Ion Composition as a Means of Investigating the Physical Origins of Alpha Particle Heavy Magnetic Switchbacks. Magnetic switchbacks are of continuing interest to the scientific community because the phenomenon has not been completely understood. Although most of the research into them in the Parker Solar Probe era has largely focused on creating a theoretical framework for causing the field reversal through magnetic interchange reconnection, reconnecting streams of plasma in the solar wind, or shear driven turbulence, it remains unclear as to what extent these models may or may not represent the underlying physical reality of magnetic switchbacks. In this paper, we present the results of our study on the energetic ion composition of magnetic switchback events using statistical methods with the aim of obtaining new insights into the underlying physics. In doing so, we find evidence that switchbacks containing suprathermal alpha flux display traits that are indicative of the Zank model of a magnetic "kink" propagating as a fast magnetosonic wave. These switchbacks also correlated with increased solar activity such as coronal mass ejections, high-speed streams, and solar flares. At the same time, switchbacks not meeting this criteria appear to occur at rates that are unaffected by increasing solar activity, which implies the existence of multiple populations of switchbacks with differing physical mechanisms behind them.

Keywords: Solar corona, Solar wind, Solar magnetic reconnection
A Novel Blast Wave Solution for the Propagation of Coronal And Interplanetary Shocks. Coronal mass ejections (CMEs) and their associated shock waves have severe space weather effects in the near-Earth space. Therefore, predicting the propagation and arrival time of the CME/shock is an important component of the space weather forecast. In this work, the analytical solutions for the propagation of blast waves are reorganized and derived, and a novel solution is obtained to describe their propagation in the background flow field moving at a constant speed. This novel solution can be used to predict the propagation and arrival time of the CME-associated shock waves in both the coronal and interplanetary medium. The input parameters of this novel solution are the shock wave's initial velocity, the piston-driving time in an analog of the initial blast process, and the background solar wind velocity. Based on the same initial conditions, we compare quantitatively the propagation processes of shock waves predicted by this novel solution and those predicted by other already existing models of the blast wave theory. The obtained results demonstrate the feasibility of this novel solution in predicting the arrival time of the interplanetary shock in the future.

Keywords: Solar-terrestrial interactions, Space weather, Interplanetary shocks, Solar coronal mass ejections
Stellar β<SUP>‑</SUP>-decay Rate of <SUP>63</SUP>Ni and Its Impact on the s-process Nucleosynthesis in Massive Stars. The β‑-decay rate of 63Ni, an important branching point, affects the subsequent nucleosynthesis in the weak component of the slow-neutron capture process (weak s-process). To evaluate the impact of the uncertainties of stellar lifetime of 63Ni on abundances, we calculate the contribution to β‑-decay rates from its excited states using the large-scale shell model with various interactions and also explore the atomic effects in the highly ionized plasma. In the core He burning stage and the shell C burning stage of massive stars, our new rates can be larger than those from K. Takahashi &amp; K. Yokoi by up to a factor of 4 and 6, respectively. We evaluate the impact of the stellar decay rates of 63Ni on the nucleosynthesis of A = 60 ∼ 90 in a star with an initial mass of 25 M⊙ and solar metallicity. We find that the new rates can lead to abundance changes of 64Ni, 63Cu, 65Cu, 64Zn, 66Zn, 67Zn, and 68Zn by up to 18%, 14%, 7%, 98%, 16%, 15%, and 13%, respectively, after the shell C burning stage at the Lagrangian mass coordinate Mr = 2M⊙. The enhancement of the decay rate of 63Ni increases the weak s-process efficiency of nuclei after 65Cu.

Keywords: Nucleosynthesis, Massive stars, Carbon burning, Helium burning, S-process
Searching for Accreting Compact Binary Systems from Spectroscopy and Photometry: Application to LAMOST Spectra. Compact objects undergoing mass transfer exhibit significant (and double-peaked) Hα emission lines. Recently, new methods have been developed to identify black hole X-ray binaries and calculate their systematic parameters using Hα line parameters, such as the full width at half-maximum (FWHM), equivalent width (EW), and separation of double peaks. In addition, the FWHM–EW plane from spectroscopy and the Hα color–color diagram from photometry can be used for rapid stellar classification. We measure the Hα and Hβ profiles (e.g., FWHM and EW) using the LAMOST DR9 low- and medium-resolution spectra, and calculate the systematic parameters (e.g., velocity semiamplitude of the donor star, mass ratio, inclination angle, and mass of the accretor). A new correlation between FWHM and K2, K2 = 0.205(18) FWHM, is obtained for cataclysmic variables (CVs) in our sample. Both the FWHM–EW plane and the Hα color–color diagram can distinguish CVs with FWHM ≳ 1000 km s‑1 from Be stars and young stellar objects to some extent. To improve classification accuracy and enhance the selection of compact objects, we propose a new set of idealized filters with effective widths of 30, 130, and 400 Å for the narrow Hα filter, broad Hα filter, and r-band filter, respectively.

Keywords: Cataclysmic variable stars, Binary stars, Black holes
Thermal Evolution of the Plasma Sheet Region in the 2017 September 10 Solar Eruption. We conduct detailed thermal analysis of the plasma sheet region during the post-eruption phase of a flare that occurred on 2017 September 10, examining the thermal properties as both a function of space and time. The plasma sheet that develops is best observed using the 131 Å and 193 Å filters of the Atmospheric Imaging Assembly on the Solar Dynamics Observatory. We use the differential emission measure technique to calculate the emission measure, emission measure weighted average temperature, density, and thermal energy inside the plasma sheet region. These quantities are calculated as a function time to assess how the conditions of the plasma sheet region change throughout the duration of the event. We find that there is a minimal decrease in the temperature as the plasma sheet region evolves. The total thermal energy in the plasma sheet is on the order of 1.5–3.0 1029 erg for the first 1.5 hr of the eruption and then decreases. For the first time for this event, we examine the conductive and radiative loss rates, which indicate rapid cooling should be expected, contradicting the temperature results. These findings suggest that there are underlying mechanisms such as adiabatic heating and/or turbulence-induced suppression of conduction that contribute to the sustained hot conditions in the plasma sheet.

Keywords: Solar activity, Solar flares, Solar magnetic reconnection
High-resolution Observations of Pickup-ion-mediated Shocks to 60 au. This study provides a detailed analysis of 14 distant interplanetary shocks observed by the Solar Wind Around Pluto instrument on board New Horizons. These shocks were observed with a pickup ion data cadence of approximately 30 minutes, covering a heliocentric distance range of ∼52–60 au. All the shocks observed within this distance range are fast forward shocks, and the shock compression ratios vary between ∼1.2 and 1.9. The shock transition scales are generally narrow, and the SW density compressions are more pronounced compared to the previous study of seven shocks by D. J. McComas et al. A majority (64%) of these shocks have upstream sonic Mach numbers greater than 1. In addition, all high-resolution measurements of distant interplanetary shocks analyzed here show that the shock transition scale is independent of the shock compression ratio. However, the shock transition scale is strongly anticorrelated with the shock speed in the upstream plasma frame, meaning faster shocks generally yield sharper transitions.

Keywords: Space plasmas, Interplanetary shocks, Heliosphere, Plasma physics, Solar wind, Pickup ions, Interplanetary particle acceleration
Strong Scatterings Invalidate Proposed Models of Enhanced Tidal Disruption Event Rates in Post-starburst Galaxies. Stars wandering too close to supermassive black holes (SMBHs) can be ripped apart by the tidal forces of the black hole. Recent optical surveys have revealed that E+A galaxies are over-represented by a factor of ∼30, while green galaxies are over-represented in both optical and IR surveys. Different stellar models have been proposed to explain this tidal disruption event (TDE) preference: ultrasteep stellar densities in the nuclear cluster, radial velocity anisotropies, and a top-heavy initial mass function (IMF). Here, we explore these hypotheses in the framework of our revised loss cone theory that accounts for both weak and strong scattering, i.e., a scattering strong enough to eject a star from the nuclear cluster. We find that when accounting for weak and strong scatterings, both ultrasteep densities and radial velocity anisotropies fail to explain the post-starburst preference of TDEs, except when considering a high anisotropy factor together with a high SMBH mass and a shallow density profile of stellar-mass BHs γbh = 7/4. Our findings hold when combining either model with top-heavy IMFs. Hence, our work emphasizes both the importance of taking into account strong scatterings and the need for new hypotheses to explain the post-starburst preference of TDEs.

Keywords: Supermassive black holes, Tidal disruption, Black holes, Galaxy nuclei
JWST NIRCam Simulations and Observations of AGN Ionization Cones in Cosmic Noon Galaxies. The extended narrow-line region (NLR) of active galactic nuclei (AGNs) provides a valuable laboratory for exploring the relationship between AGNs and their host galaxies, often appearing as an "ionization cone" that can extend out to the very edge of the galaxy. We use new James Webb Space Telescope NIRCam imaging to study the morphologies and sizes of NLRs traced by [O III] at cosmic noon (z ∼ 2─3). To determine NIRCam's ability to probe the properties of the NLR in cosmic noon galaxies, we present simulated images of AGNs at z = 2─3 created with archival data cubes from the Multi Unit Spectroscopic Explorer of nine nearby (z &lt; 0.05) AGN host galaxies with previously confirmed extended NLRs. Our simulated images show that NIRCam is able to resolve the morphologies of NLRs at z = 2─3 with narrow- and medium-band observations. We then search for extended NLRs with NIRCam medium-band observations targeting the [O III] + Hβ emission in 27 previously identified AGNs at z = 2.4─3.4 in the Great Observatories Origins Deep Survey South field. We detect six galaxies in our observed sample with [O III] + Hβ morphologies consistent with AGN ionization cones with characteristic NLR sizes of 1─2.5 kpc. Thanks to our simulated data, we can predict the effects of cosmological surface brightness dimming and instrument noise on the NLR size measurements at high redshift, which has the biasing effect of lowering the NLR size─AGN luminosity trend that is observed at low redshift by a factor of ∼2.

Keywords: Emission line galaxies, James Webb Space Telescope, Seyfert galaxies, Active galactic nuclei, High-redshift galaxies