Sazuna/UAT_keywords huggingface dataset:
The Impact of Stellar Rotations and Binaries on the Shape of Upper Main Sequence near Turnoff in Open Cluster NGC 6067. We present the analysis of the extended main-sequence turnoff (eMSTO) in the open cluster NGC 6067. We derive the projected rotational velocity, vsini, of the stars belonging to the eMSTO region of the main sequence (MS) utilizing Gaia-ESO spectra. Our results reveal a positive correlation between vsini and the color of eMSTO stars, where fast-rotating stars predominantly occupy the red part of the MS while slow-rotating ones prefer a bluer side of the MS. The gravity-darkening effect might be a reason for this correlation. We find that most of the close binaries present in the eMSTO population would be slow-rotating due to the tidal-locking phenomenon. We identify four double-lined spectroscopic binaries (SB2) featuring slow-rotating companions, further supporting this tidal-locking hypothesis. However, the spatial distribution and the cumulative radial distribution indicate a higher concentration of red eMSTO stars in the cluster's central region than their bluer counterparts. This suggests that tidal locking is less likely to be the cause of the observed spread in rotation rates among eMSTO stars. Instead, we propose that star─disk interactions during the pre-main-sequence phase might have played a crucial role in spreading the rotation rates of stars, leading to the eMSTO phenomenon in NGC 6067.

Keywords: Close binary stars, Spectroscopy, Open star clusters, Stellar rotation, Blue straggler stars
Constraints on Fast Radio Burst Population from the First CHIME/FRB Catalog with the Hierarchical Bayesian Inference. Fast radio bursts (FRBs) have emerged as one of the most dynamic areas of research in astronomy and cosmology. Despite increasing number of FRBs having been reported, the exact origin of FRBs remains elusive. Investigating the intrinsic redshift distributions of FRBs could provide valuable insights into their possible origins and enhance the power of FRBs as a cosmological probe. In this paper, we propose a hierarchical Bayesian inference approach combining with several viable models to investigate the redshift distribution of the Canadian Hydrogen Intensity Mapping Experiment/FRB catalog 1. By utilizing this method, we aim to uncover the underlying patterns and characteristics of the FRB population, i.e., the intrinsic redshift distribution of FRB. Taking uncertainties within the observational data and selection effects into consideration, we found that the redshift distribution of FRBs is significantly delayed with respect to that of the star formation history.

Keywords: Radio transient sources
Modeling the Multiwavelength Emission of 3C 279 during the 14 yr Fermi-LAT Era. We report the results of our long-term multiwavelength spectral energy distribution (SED) study on the flat-spectrum radio quasar 3C 279 during the ∼14 yr (2008─2022) Fermi-Large Area Telescope (LAT) observing period. The Fermi-LAT data were complemented with data in other wave bands obtained from the Swift-X-Ray Telescope (XRT)/UVOT, the Whole Earth Blazar Telescope, along with other optical and radio data from several observatories. Different activity states were identified from the weekly binned γ-ray light curve, and it was possible to create 168 high-quality and quasi-simultaneous broadband SEDs. We modeled the SEDs using a one-zone leptonic scenario, including the emission region outside the broad-line region (BLR), involving synchrotron, synchrotron self-Compton, and external Compton mechanisms. Such extensive broadband modeling is essential for constraining the underlying multiwavelength radiative mechanisms in the 3C 279 jet and permits the estimation of the physical parameters and exploration of their evolution in time. Our SED modeling study suggests that the increase in the Doppler beaming factor, along with the variation of the emitting electrons, is the cause for the flares in this source. The multiwavelength emission of 3C 279 was found to be well explained by the scenario in which the emission region is outside the BLR at a distance of ∼6.42 × 103RS. However, for two of the very bright γ-ray states, the emission region was found to be close to the outer boundary of the BLR at a distance of ∼1.28 × 103RS from the central black hole.

Keywords: Jets, Active galactic nuclei, Gamma-rays, Quasars
Tera-Hertz Counterparts to Fast Radio Bursts from Coherent Cherenkov Radiation by Tilted Bunches. Fast radio bursts (FRBs) are millisecond-duration extragalactic transients characterized by ultrahigh brightness temperatures, suggesting coherent emission mechanisms in extreme astrophysical processes. In this paper, we extend the bunched coherent Cherenkov radiation (CChR) framework by incorporating bunch inclination and geometric configuration parameters, enabling it to more rigorously model FRB emission and tera-Hertz (THz) emission from magnetars. When relativistic bunches are injected into the magnetized plasma of a magnetar's magnetosphere at the Cherenkov angle, their emitted waves achieve phase coherence through constructive interference. Furthermore, the three-dimensional geometry of the bunches plays a crucial role in influencing the coherence of the radiation. Within the framework of CChR, we predict the existence of THz emission counterparts associated with FRBs and explain the observed characteristics of the THz-emitting magnetar SGR J1745-2900. Detections of such counterparts by upgraded millimeter telescopes (e.g., Atacama Large Millimeter/submillimeter Array, IRAM) would be expected to provide new insights into the potential physical connection between FRBs and magnetars.

Keywords: Magnetars, Radio bursts, Radiative processes, Radio transient sources
PSR J1735–0243: A Pulsar with Three Cone Components Exhibiting Mode-changing Behavior. We have carried out a detailed analysis of PSR J1735‑0243 with the Five-hundred-meter Aperture Spherical radio Telescope at 1250 MHz. We found that this pulsar shows obvious mode changing, with approximately 82% in the normal mode and approximately 18% in the abnormal mode. The two modes differ not only in their integrated pulse profiles but also in their polarization properties. Further analyses suggest that the emission from the normal mode may originate from a higher height than the abnormal mode. Additionally, we found that the radio emission beam consists of four emission components, including a core component and three cone components. The tertiary cone component, which has the highest emission height, is present in both emission modes. Finally, the results shown that the radio emission of PSR J1735‑0243 may have been generated in the core gap region.

Keywords: Radio pulsars
JVLA and VLBA Study of the Merging Cool Core CHIPS 1911+4455 at z ∼ 0.5 Radio Emission from an Infant Active Galactic Nucleus and from a Rapidly Star-forming Brightest Cluster Galaxy. Recent studies of galaxy clusters found peculiar cases at the boundary between noncool core and cool core systems. While unusual, these objects can help us understand the evolution of the most massive clusters. We investigated the role of active galactic nucleus (AGN) feedback in the starburst brightest cluster galaxy (BCG) of the merging cool core cluster CHIPS 1911+4455 (z = 0.485). We conducted new multifrequency (0.3─5 GHz) Very Long Baseline Array (VLBA) and Jansky Very Large Array (JVLA) observations of CHIPS 1911+4455 across a wide range of scales (0.01─20 kpc). Our analysis reveals that the AGN in the BCG has recently awakened, showing a compact core with symmetric, ∼30 pc long jets in VLBA data. The onset of the AGN may be linked to the enhanced cooling of the hot gas found in a previous study. At larger scales (10 kpc), faint radio whiskers extending to the south show a striking alignment with star-forming knots and are thus interpreted as synchrotron-emitting regions associated with the starburst BCG. The implied radio star formation rate of 100─155 M⊙ yr−1 agrees with the optical/infrared one (140−190 M⊙ yr−1). Our JVLA and VLBA radio study, informed by previous X-ray/optical/millimeter works, indicates that CHIPS 1911+4455 represents a transitional phase in cluster evolution, where the AGN in the central galaxy has just begun to respond to copious hot gas cooling.

Keywords: Galaxy clusters, Radio cores, Active galactic nuclei, Star formation, Brightest cluster galaxies, Intracluster medium
Nonlinearity of 3 minute Slow Magnetoacoustic Waves in the Sunspot Umbral Atmosphere. Slow magnetoacoustic waves with a 3 minute period are upward-propagating waves traveling through the density-stratified umbral atmosphere. The decreasing density causes their amplitude to increase, developing into nonlinear waves through steepening and eventually forming shocks. To investigate the vertical evolution of this wave nonlinearity, we utilized multiwavelength data from the Atmospheric Imaging Assembly (AIA) onboard the Solar Dynamics Observatory, covering from the photosphere to the lower corona across 20 active regions. The steepening of the wave profile leads to the generation of higher harmonics. We quantify this using a nonlinearity index (NI), defined as the ratio of the amplitude of the second harmonic to the fundamental obtained using wavelet analysis. We find a characteristic pattern: nonlinearity increases from the photosphere through the lower chromosphere, peaking near the AIA 1700 Å formation height, and decreases at higher altitudes, notably in the AIA 304 Å channel. This trend indicates progressive wave steepening and subsequent energy dissipation before reaching the formation of AIA 304 Å, consistent with shock formation in the lower atmosphere. An additional rise in NI is observed at the AIA 131 Å channel, followed by a decline in AIA 171 Å, suggesting a second phase of wave nonlinearity evolution in the lower corona. Based on the NI profile and the formation heights of these channels, we conjecture that nonlinear wave processes are most prominent between the AIA 1700 Å and AIA 304 Å formation layers and again between AIA 131 Å and AIA 171 Å.

Keywords: Magnetohydrodynamics, Sunspots, Solar magnetic fields, Wavelet analysis, Solar oscillations
Constraining the Faint-end Slope of the Fast Radio Burst Energy Function Using CHIME/FRB Catalog-1 and Local Volume Galaxies. Despite hundreds of detected fast radio bursts (FRBs), the faint-end slope (γ) of their energy distribution remains poorly constrained, hindering understanding of whether bright, cosmological FRBs and faint, Galactic magnetar SGR 1935+2154-like bursts share a common origin. In this study, we constrain this faint-end slope, modeled with a Schechter-like distribution, by searching for potential associations between bursts from the CHIME/FRB Catalog-1 and galaxies in the Local Volume. We crossmatched CHIME/FRB Catalog-1 FRBs with 495 Local Volume galaxies within 21 Mpc, identified from the HECATE catalog, and found no associations. Assuming the FRB energy function extends to ∼3 × 1034 erg—the energy of the Galactic magnetar burst from SGR 1935+2154—this null result constrains γ to be &lt;2.3 (95% confidence upper limit), representing the first empirical estimate for extragalactic FRBs at such low energies. This finding supports the hypothesis that the FRB population is dominated by bright, likely cosmological bursts with a relatively flat energy distribution (γ &lt; 2.5). However, the constraint weakens if higher-energy thresholds are assumed. A flatter energy function is consistent with the observed anticorrelation between FRB dispersion measure and fluence, as seen across various observational bands. While the contribution of low-energy bursts, such as those from the Galactic magnetar SGR 1935+2154, appears minimal, our results suggest that normal magnetars like SGR 1935+2154 could dominate the FRB population if their burst rates and energies scale with age and magnetic field. The upcoming CHIME/FRB Catalog-2 data and targeted nearby galaxy surveys will further refine these constraints, offering critical insight into whether FRBs arise from a single population or diverse origins.

Keywords: Neutron stars, Luminosity function, Extragalactic radio sources, Galaxies, Radio transient sources
Parsec-scale SiO Emission in the Galactic Center. The central 5 pc of our Galactic center is rich in various molecular tracers. The region is observed to be hot, highly ionized, and volatile, resulting in complex chemistry and kinematics. Countless molecular observations of the central region orbiting the central supermassive black hole Sgr A* have revealed a stable grouping of clouds with a disklike structure known as the circumnuclear disk (CND) orbiting Sgr A* between 1.5 and 3 pc. The CND houses the densest population of gas outside the ionized streams in the minispiral falling onto Sgr A*. However, the small-scale kinematics of the clouds and gas are poorly understood in this region. In this paper, we report single-dish SiO (1–0) observations of the central 5 pc surrounding Sgr A* taken with the Green Bank Telescope. Most of the SiO (1–0) traces the Southern Streamer and Sgr A East—neither of which are associated with the CND. However, one region in the CND, known as the Northeast (NE) Arm, shows high-intensity SiO emission unlike in the rest of the CND, indicating the NE Arm as a candidate region of either cloud–cloud collision or early star formation. Further high-resolution observations of the region are needed to distinguish between the two scenarios.

Keywords: Galaxy circumnuclear disk, Galactic center
MINDS: Detection of an Inner Gas Disk Caused by Evaporating Bodies around HD 172555. Mechanisms such as collisions of rocky bodies or cometary activity give rise to dusty debris disks. Debris disks trace the leftover building blocks of planets, and thus also planetary composition. HD 172555, a stellar twin of β Pic, hosts a debris disk thought to have resulted from a giant collision. It is known for its extreme mid-infrared silica dust feature, indicating a warm population of silica-rich grains in the asteroid belt (∼5 au), cold CO observed by Atacama Large Millimeter/submillimeter Array (ALMA), and small bodies evaporating as they approach close to the star. Our JWST Mid-InfraRed Instrument/Medium Resolution Spectroscopy (MIRI MRS) observations now reveal emission from an inner gaseous disk (&lt;0.5 au) that arises from the evaporation of close-in material. For the first time in a debris disk, we detect neutral atomic chlorine and sulfur, as well as ionized nickel. We recovered the neutral sulfur line in ∼20 yr old Spitzer data, showing it is long-lived and stable. Ionized iron, previously seen only in β Pic, is also detected. All lines are broadened by Keplerian rotation, pinpointing the gas location. The HD 172555 system serves as a unique laboratory to study the composition of planetesimals, asteroids, and comets beyond the solar system. The comparison to β Pic reveals that the gas in HD 172555 is hotter, closer to the star, and poor in argon—suggesting it originates from evaporating rocky bodies near the star, while β Pic's gas may trace volatile-rich bodies from larger separations.

Keywords: A stars, Exoplanets, James Webb Space Telescope, Spectroscopy, Circumstellar disks, Circumstellar dust, Exocomets, Debris disks
Coronal Mass Ejection–Induced Sub-Alfvénic Solar Wind: Key Insights from Parker Solar Probe. Since its eighth encounter, starting on 2022 April 28, Parker Solar Probe has consistently sampled the elusive sub-Alfvénic solar wind during each perihelion pass, offering unprecedented insights into these critical regions of the solar atmosphere. Here, we analyze sub-Alfvénic solar wind intervals longer than 10 minutes during the 10th encounter. The plasma sampled during these intervals shares some common features: considerable density drop relative to the surrounding plasma, very low plasma beta (βp), significantly reduced levels of magnetic field fluctuations, and high magnetic field variance anisotropy (transverse to the mean field). Interestingly, no switchbacks are observed in the analyzed sub-Alfvénic regions. We explore the potential role of coronal mass ejections (CMEs) in generating sub-Alfvénic wind regions. Remarkably, we find that every extended sub-Alfvénic wind interval during encounter 10 is linked to a CME. While all the observed sub-Alfvénic intervals are associated with CME wakes, the latter also has periods that are super-Alfvénic.

Keywords: Solar coronal transients, Solar wind, Interplanetary magnetic fields, Solar coronal mass ejections
Hidden Binaries in Star-forming Regions. A significant fraction of, and possibly all, stars form in binary or multiple systems. For solar-mass stars in the Galactic field, the distribution of orbital separations is log-normal over 7 orders of magnitude, from 10‑2 to 105 au. In contrast, the separation distributions of systems in nearby star-forming regions paint a much more confusing picture. There appears to be an excess of systems in the separation range 10–1000 au, and recent high-resolution spectroscopic observations of close (&lt;10 au) systems suggest a field-like distribution in some star-forming regions, but a possible excess with respect to the field in other regions. Furthermore, the resolution limit of numerical simulations of binary star formation is ∼1 au, and consequently, comparisons with the binary distributions in star-forming regions and in the field are restricted. In this paper, we demonstrate that these observational uncertainties and limitations in the simulations are potentially a much bigger problem than previously realised. We show that the log-normal separation distribution in the field can be reproduced by combining constituent binary populations whose initial separation distributions have a very different form from a log-normal. We also argue that the observed excess of binaries in the range 10–62 au in the Orion Nebula Cluster (ONC) compared to the Galactic field is not necessarily inconsistent with the field population, because the ONC is only one of many star-forming regions that populate the field. We propose that further observations of spectroscopic binaries in star-forming regions to probe and complete the &lt;10 au parameter space are urgently needed.

Keywords: Binary stars, Close binary stars, Star forming regions, Spectroscopic binary stars, Star formation
Neutron Star Stability beyond the Mass Peak: Assessing the Role of Out-of-equilibrium Perturbations. We investigate the radial stability of neutron stars under conditions where their composition may or may not remain in chemical equilibrium during oscillations. Using different equations of state that include nucleons, hyperons, and/or Δ resonances, we compute stellar configurations and examine their fundamental mode frequencies in two limiting scenarios. In one limit, nuclear reactions are fast enough to maintain chemical equilibrium throughout the pulsation, resulting in a lower adiabatic index, ΓEQ, and softer stellar responses. In the opposite limit, nuclear reactions are too slow to adjust particle abundances during oscillations, yielding a higher index, ΓFR, and stiffer stellar responses. We find that the equilibrium scenario triggers dynamic instability at the maximum-mass configuration, whereas the frozen composition scenario allows stable solutions to persist beyond this mass, extending the stable branch. This effect is modest for simpler equations of state but becomes increasingly pronounced for more complex compositions, where a complex interplay between the available degrees of freedom due to the emergence of new particle species and the values of the coupling constants leads to a significant disparity between ΓEQ and ΓFR. Realistic conditions, in which different nuclear reactions have distinct timescales, will place the effective Γ between these two extreme values, thereby limiting the length of the extended branch relative to the fully frozen limit studied here. We also explore astrophysical scenarios in which the extended branch may be populated and outline the multimessenger observations that could reveal its presence.

Keywords: Neutron stars
Magellan Spectroscopy of Active Galactic Nuclei in Low-mass Galaxies: Scaling Relations and a Triple-peaked Active Galactic Nucleus. In this work, we aim to further populate the low-mass regime of black hole (BH) scaling relations to better understand the formation and growth mechanisms of central supermassive BHs. We target six galaxies that have been previously identified as hosting active galactic nuclei (AGNs) based on optical spectroscopy from the Galaxy and Mass Assembly survey or the Sloan Digital Sky Survey with stellar masses reported to be M⋆ &lt; 5 × 109 M⊙. Using follow-up optical spectroscopy from the Magellan Echellette Spectrograph, we extract galaxy velocity dispersions (σ⋆) and estimate virial BH masses from broad Hα emission. We find that the galaxies in our sample do not deviate significantly from either the MBH‑σ* or MBH‑M* scaling relations defined by higher-mass galaxies. Additionally, we identify one galaxy with triple-peaked [S II], [N II], Hα, and Hβ emission lines. This spectral shape is not shared by [O III] and, in fact, the [O III] line appears to have distinct kinematics from the other emission lines. Incorporating the spatial distribution of the various emission lines, we find that the galaxy spectrum is consistent with a prominent central AGN driving an outflow, surrounded by an extended ring/disk of gas predominantly ionized by shocks and/or star formation. This work has implications for the demographics of BHs in low-mass galaxies and the role of AGN feedback.

Keywords: Active galaxies, Galaxy evolution, Scaling relations
Resolving the Origin of the Unidentified TeV Source HESS J1626-490 as a Relic of the Ancient Cosmic-Ray Factory SNR G335.2+0.1. While decades of observations in the TeV gamma-ray band have revealed more than 200 sources with radio or X-ray counterparts, there remain dozens of unidentified TeV sources, which may provide crucial information of cosmic-ray (CR) accelerators. HESS J1626‑490 is an unidentified TeV gamma-ray source but is expected to originate from CRs that escaped from the nearby supernova remnant (SNR) G335.2+0.1 and are interacting with dense interstellar clouds. To test this scenario, we scrutinize the properties of the SNR and search for nonthermal counterparts by analyzing observational data in the radio, X-ray, and GeV gamma-ray bands. From analysis of the H I and 12CO (J = 1–0) line data, we identify the cloud associated with the SNR and compare the morphologies of the cloud and the gamma-ray emission. The distance and age of the SNR are estimated to be 3.3 ± 0.6 kpc and ∼5 kyr, respectively. From X-ray and GeV gamma-ray data analyses, we find an extended GeV gamma-ray emission overlapping with the SNR and H.E.S.S. source regions but no X-ray emission. The location of the peak of the extended GeV emission changes from near the SNR at ≲1 GeV to the H.E.S.S. source at &gt;10 GeV. We find a spectral hardening at ∼50 GeV, which is consistent with the existence of two components in the gamma-ray emission. We find that a combination of emission from the escaped CRs and the SNR itself can reproduce the observed broadband spectrum, on the assumption that the SNR has accelerated protons to ≳100 TeV in the past.

Keywords: Galactic cosmic rays, Supernova remnants, Cosmic ray sources, Interstellar medium, Gamma-ray astronomy, Cosmic rays