Sazuna/UAT_keywords huggingface dataset:
Dynamic Photometric Variability in Three Young Brown Dwarfs in Taurus: Detection of Optical Flares with TESS Data. We present I-band time-series photometric variability studies of three known nearby (∼140 pc) and young (∼1 Myr) brown dwarfs (BD) in the Taurus star-forming region in the Perseus molecular cloud. From 10 nights of observations over a time span of 10 yr, with a typical run of 3–6 hr each night, we estimated that the BDs show unstable short-scale periodicity from 1.5 to 4.8 hr. Using the long-term photometry from the Transiting Exoplanet Survey Satellite (TESS), we have conducted a time-resolved variability analysis of CFHT-BD-Tau 3 and CFHT-BD-Tau 4, revealing orbital periods of ∼0.96 days and ∼3 days respectively, consistent with earlier studies. We also found two superflares in TESS sector 43 data for CFHT-BD-Tau 4 and estimated the flare energies as 7.09 × 1035 erg and 3.75 × 1036 erg. A magnetic field of ∼3.39 kG is required to generate such flare energies on this BD. We performed spot modeling analysis on CFHT-BD-Tau 3 and CFHT-BD-Tau 4 to address the variability detected in the data using the package BASSMAN. Spectral energy distribution and infrared colors of the sources suggest that they have a sufficient amount of circumstellar material around them.

Keywords: Starspots, Brown dwarfs, Space telescopes, Stellar activity, Low mass stars, Variable stars, Optical flares, Photometry, Ground-based astronomy, Stellar rotation, Atmospheric variability
Simulating the Arrival of Multiple Coronal Mass Ejections That Triggered the Gannon Superstorm on 2024 May 10. The 2024 May 10 space weather event stands out as the most powerful storm recorded during the current solar cycle. This study employs a numerical framework utilizing a semiempirical coronal model, along with heliospheric upwind extrapolation with time dependence and cone coronal mass ejection (CME) models for the inner heliosphere, to forecast solar wind velocity and the arrival of CMEs associated with this event. The simulations were also carried out using the Space Weather Adaptive Simulation framework and a drag-based model (DBM) for this complex event of multiple CMEs. Predicted arrival times and velocities from these models are compared with actual observations at the Sun–Earth L1 point. These simulations reveal that three CMEs reached Earth nearly simultaneously, resulting in the extreme space weather event, followed by the arrival of a few more eruptions. The simulations accurately predicted arrival times with a discrepancy of approximately 5 hr or less for these CMEs. Further, the ensemble study of the DBM shows the sensitivity of the CME arrival time to the background solar wind speed and drag parameters. All three models have done fairly well in reproducing the arrival time closely to the actual observation of the CMEs responsible for the extreme geomagnetic storm of 2024 May 10. These rare solar storms offered a unique opportunity to thoroughly evaluate and validate our advanced models for predicting their arrival at Earth.

Keywords: Heliosphere, Space weather, Solar wind, Solar coronal mass ejections, Solar-terrestrial interactions
Empirical Constraints on Tidal Dissipation in Exoplanet Host Stars. The orbits of short-period exoplanets are sculpted by tidal dissipation. However, the mechanisms and associated efficiencies of these tidal interactions are poorly constrained. We present robust constraints on the tidal quality factors of short-period exoplanetary host stars through the usage of a novel empirical technique. The method is based on analyzing structures in the population-level distribution of tidal decay times, defined as the time remaining before a planet spirals into its host star due to stellar tides. Using simple synthetic planet population simulations and analytic theory, we show that there exists a steady-state portion of the decay time distribution with an approximately power-law form. This steady-state feature is clearly evident in the decay time distribution of the observed short-period planet population. We use this to constrain both the magnitude and frequency dependence of the stellar tidal quality factor and show that it must decrease sharply with planetary orbital period. Specifically, with  , we find 105.5 ≲ Q0 ≲ 107 and ‑4.33 ≲ α ≲ ‑2. Our results are most consistent with predictions from tidal resonance locking, in which the planets are locked into resonance with a tidally excited gravity mode in their host stars.

Keywords: Hot Jupiters, Exoplanets, Exoplanet tides, Tides, Planetary dynamics
The Formation Histories of Massive and Quiescent Galaxies in the 3 &lt; z &lt; 4.5 Universe. We present the formation histories of 19 massive (≳3 × 1010M⊙) quiescent (specific star formation rate, sSFR &lt; 0.15 Gyr‑1) galaxy candidates at z ~ 3.0–4.5 observed using JWST/NIRSpec. This completes the spectroscopic confirmation of the 24 K-selected quiescent galaxy sample from the ZFOURGE and 3DHST surveys. Utilizing Prism 1–5 μm spectroscopy, we confirm that all 12 sources that eluded confirmation by ground-based spectroscopy lie at z &gt; 3, resulting in a spectroscopically confirmed number density of ~1.4 × 10‑5 Mpc‑3 between z ~ 3 and 4. Rest-frame U ‑ V versus V ‑ J color selections show high effectiveness in identifying quiescent galaxies, with a purity of ~90%. Our analysis shows that parametric star formation histories (SFHs) from FAST++ and binned SFHs from Prospector on average yield consistent results, revealing diverse formation and quenching times. The oldest galaxy formed ~6 × 1010M⊙ by z ~ 10 and has been quiescent for over 1 Gyr at z ~ 3.2. We detect two galaxies with ongoing star formation and six with active galactic nuclei (AGNs). We demonstrate that the choice of stellar population models, stellar libraries, and nebular or AGN contributions does not significantly affect the derived average SFHs of the galaxies. We demonstrate that extending spectral fitting beyond the rest-frame optical regime reduces the inferred average star formation rates (SFRs) in the earliest time bins of the SFH reconstruction. The assumed SFH prior influences the SFR at early times, where spectral diagnostic power is limited. Simulated z ~ 3 quiescent galaxies from IllustrisTNG, SHARK, and Magneticum broadly match the average SFHs of the observed sample but struggle to capture the full diversity, particularly at early stages. Our results emphasize the need for mechanisms that rapidly build stellar mass and quench star formation within the first billion years of the Universe.

Keywords: Galaxy evolution
One-dimensional Linear Analysis and Numerical Simulations of Alfvén Waves in a Force-free Magnetosphere around a Kerr Black Hole. We perform 1D linear analysis and numerical simulations of the propagation of Alfvén waves in a force-free magnetosphere along magnetic field lines around a spinning black hole. We use the results to investigate the dynamic process of wave propagation and energy transport for Alfvén waves. As in a previous study using the Banados–Teitelboim–Zanelli spacetime, the Alfvén wave induces a fast magnetosonic wave in the case of a spinning black hole. Energy conservation is confirmed when this additional induced magnetosonic wave is considered. We also observe the reflection of the inwardly propagating Alfvén wave around the static limit, which is prohibited in theory when using the eikonal approximation.

Keywords: Alfven waves, Magnetohydrodynamics, Plasma astrophysics, Kerr black holes
Unveiling the Interior Structure and Thermal Evolution of Super-Earth GJ 486b. Recent ground- and space-based surveys have shown that planets between Earth and Neptune in size, known as "super-Earths," are among the most frequently found planets in the Galaxy. Although the JWST era has provided high-quality atmospheric data on many such super-Earths, modeling tools are crucial for understanding their unobservable interiors. Consequently, interior studies represent the next essential step in gaining a comprehensive understanding of this class of exoplanets. This study investigates the interior structure, thermal evolution, and atmospheric dynamics of the super-Earth GJ 486b using SERPINT, a 1D self-consistent coupled interior structure and evolution model, aiming to understand the planet's thermal evolution based on an Earth-like structure. Our results indicate that GJ 486b's core is approximately 1.34 times larger than Earth's, with a core pressure of about 1171 GPa. The thermal evolution model predicts that the planet's mantle cools and solidifies over approximately 0.93 Myr. As the magma ocean cools, water is released from the melt, forming a water-rich atmosphere during early solidification. Photolysis of water vapor and subsequent hydrogen escape lead to oxygen accumulation, forming a water- and oxygen-rich secondary atmosphere. Future high-sensitivity JWST observations, with improved wavelength coverage and the detection of additional trace gases, will enable a detailed analysis of the planet's atmospheric composition, providing crucial insights into the interior, surface, and subsurface properties of GJ 486b.

Keywords: Extrasolar rocky planets, Super Earths, Planetary interior, Exoplanets
The Circumgalactic Medium Traced by Mg II Absorption with DESI: Dependence on Galaxy Stellar Mass, Star Formation Rate, and Azimuthal Angle. Understanding the circumgalactic medium (CGM) distribution of galaxies is the key to revealing the dynamical exchange of materials between galaxies and their surroundings. In this work, we use the DESI Early Data Release data set to investigate the cool CGM of galaxies (0.3 &lt; z &lt; 1.7) by stacking the spectra of background quasi-stellar objects to obtain the Mg II absorption of foreground galaxies. The equivalent width of Mg II absorption strongly correlates with stellar mass, with EW(Mg II)   for star-forming galaxies with  , but is independent of mass for galaxies above this mass. At a given stellar mass, EW(Mg II) is larger for galaxies of higher star formation rate with an impact parameter less than 50 kpc, while showing little dependence on galaxy size. By studying the dependence on azimuthal angle, we find EW(Mg II) is strongest at the direction near the minor axis for star-forming galaxies with  , while no dependence on azimuthal angle is seen for luminous red galaxies. This indicates that the outflow associated with star formation enhances the Mg II absorption. However, for galaxies with  , the EW(Mg II) at the minor axis is largely suppressed with respect to low-mass galaxies. This suggests that the competing processes, such as stellar feedback and gravity, play a key role in shaping the distribution of outflowing gas.

Keywords: Quasar absorption line spectroscopy, Circumgalactic medium
Parallel Electric Fields and Electron Heating Observed in the Young Solar Wind. The largest electric fields between 18 and 30 solar radii are in narrowband waves simultaneously observed at a few Hz (somewhat above the local proton gyrofrequency) and a few hundred Hz (far below the lower hybrid frequency), with the higher-frequency wave triggered at specific phases of the lower-frequency wave. This wave pair, called "triggered ion-acoustic waves" (TIAWs), has been shown to both be physical and to occur at times of electron heating. A theory of electron heating and acceleration by the low-frequency wave has been presented. While this theory and the TIAW results strongly suggest the presence of low-frequency electric fields that are parallel to the local magnetic field, such fields have not been directly observed. In this paper, such parallel electric field observations are reported, and TIAWs are further described to conclude that they occur during about 75% of the Parker Solar Probe passes through 18–30 solar radii, and when present, they are the dominant wave signal, lasting for hours. In the presence of these parallel electric fields, electrons are heated while, in their absence, there is no electron heating. That there is no heating between 18 and 30 solar radii in the absence of TIAWs is a most significant result because it invalidates other proposed mechanisms that predict heating in this radial range all of the time.

Keywords: Solar coronal waves, Plasma physics
Probing 3D Magnetic Fields Using Starlight Polarization and Grain Alignment Theory. Polarization of starlight induced by dust grains aligned with the magnetic field (hereafter B-field) is widely used to measure the 2D B-fields projected onto the plane-of-sky. Here, we introduce a new method to infer 3D B-fields using starlight polarization. We show that the inclination angle or line-of-sight component of B-fields can be constrained by the starlight polarization efficiency from observations, the alignment degree provided by the magnetically enhanced radiative torque (MRAT) alignment theory, and the effect of B-field tangling. We first perform synthetic observations of starlight polarization of magnetohydrodynamic (MHD) simulations of a filamentary cloud with our updated POLARIS code incorporating the modern MRAT theory. We test the new technique with synthetic observations and find that the B-field inclination angles can be accurately determined by the synthetic starlight polarization efficiency once the effects of grain alignment, dust properties, and B-field fluctuations are well characterized. The technique can provide an accurate constraint on B-field inclination angles using optical polarization in low-density regions AV &lt; 3 with efficient MRAT alignment, whereas the technique can infer further to high-density regions with significant alignment loss at AV ∼ 8–30 by using near-infrared polarization. Our new technique unlocks the full potential of tracing 3D B-fields and constraining dust properties and grain alignment physics on multiple scales of the diffuse interstellar medium and star-forming regions using multiwavelength starlight polarization observations.

Keywords: Interstellar magnetic fields, Starlight polarization, Star formation, Interstellar medium
Neutrinos from Carbon-burning Red Supergiants and Their Detectability. Stars emit megaelectronvolt neutrinos during their evolution via nuclear syntheses and thermal processes, and detecting them could provide insights into stellar structure beyond what is accessible through electromagnetic wave observations. So far, megaelectronvolt neutrinos have been observed from the Sun and SN 1987A. It has been suggested that pre-supernova stars in the oxygen- and silicon-burning stages would emit enough megaelectronvolt neutrinos to be detectable on Earth, provided they are in the local Universe. In this study, we investigate the prospect of detecting neutrinos from red supergiants (RSGs) in the carbon-burning phase. In our Galaxy, around a thousand RSGs have been cataloged, and several are expected to be in the carbon-burning phase. We first calculate the luminosity and energy spectrum of the neutrinos emitted during the post-main-sequence evolution of massive stars. For a nearby carbon-burning RSG located ∼200 pc away, we estimate the neutrino flux reaching Earth to be as large as ∼105 cm‑2 s‑1, with a spectrum peaking at ∼0.6 MeV. We then assess the feasibility of detecting these neutrinos in underground facilities, particularly in hybrid detectors equipped with a water-based liquid scintillator and ultrafast photodetectors. In detectors with a volume comparable to Super-Kamiokande, for the above flux, we anticipate up to ∼50 neutrino events per year with directional information. Although this is a fair number, the number of events from radioactive backgrounds would be much larger. Our results indicate that studying neutrinos from carbon-burning RSGs and predicting supernovae well in advance before their explosion would be challenging with currently available detector technologies.

Keywords: Neutrino telescopes, Neutrino astronomy, Carbon burning, Stellar evolution
Spectra of He Isotopes and the <SUP>3</SUP>He/<SUP>4</SUP>He Ratio. Since its launch, the Alpha Magnetic Spectrometer-02 (AMS-02) has delivered outstanding quality measurements of the spectra of cosmic-ray (CR) species, e±,  , and nuclei (H–Si, S, Fe), which have resulted in a number of breakthroughs. Besides elemental spectra, AMS-02 also measures the spectra of light isotopes albeit within a smaller rigidity range. In this paper, we use the precise measurements of He isotopes and the 3He/4He ratio by AMS-02, together with Voyager 1 data, and investigate their origin. We show that there is an excess in 3He at higher energies compared to standard calculations assuming its fully secondary origin, which may indicate a source of primary 3He, or signify a change in the propagation parameters over the Galactic volume probed by the 3He/4He ratio. We provide updated local interstellar spectra (LIS) of 3He and 4He in the rigidity range from 2 to 40 GV. Our calculations employ the self-consistent GALPROP–HELMOD framework that has proved to be a reliable tool in deriving the LIS of CR e‑,  , and nuclei Z ≤ 28.

Keywords: Galactic cosmic rays, Secondary cosmic rays, Heliosphere, Cosmic rays
Investigating the Effects of Atmospheric Stratification on Coronal Active Region Field Modeling. Understanding the evolution of the complex magnetic fields found in solar active regions is an active area of research. There exist many different models for such fields, which range in their complexity due to the number of physical effects included in them—one common factor being that they all extrapolate the field up from the photosphere. In this study, we focus on the fact that above the photosphere and below the corona lies the relatively cool and dense chromosphere—which is often neglected in coronal models, due to it being comparatively thin and difficult to model. We isolate and examine the effect including this boundary layer has on a 2.5D class of driven MHD models of an active region eruption. We find that it can result in significant changes to the dynamics of an erupting field far higher in the atmosphere than the chromosphere itself, generally delaying eruptions and increasing the magnetic energy released in each eruption. We also test whether these effects can be approximated using a variation of the more computationally efficient magnetofrictional model, finding a number of simple adaptations of the standard magnetofrictional model, which capture the effect of the chromospheric stratification well.

Keywords: Solar atmosphere, Solar coronal mass ejections, Solar corona, Solar transition region
Cataloging Stream Interaction Regions at MAVEN: A Cross-comparative Study with STEREO-A. Stream interaction regions (SIRs) are long-lasting solar wind structures that result from stable fast solar wind interacting with preceding slow solar wind. These structures have been examined in depth throughout the heliosphere, particularly at 1 au; however, due to sparse observations, SIRs have not been characterized thoroughly at 1.5 au. Thanks to the Mars Atmosphere and Volatile EvolutioN (MAVEN) mission, we have a chance to fill this observational gap. We implement in situ solar wind data collected by MAVEN to identify SIRs between 2014 November and 2023 September. We observe 185 SIRs with average durations of 2.2 days that occur primarily during periods of low solar activity. We detect 19 forward shocks, seven reverse shocks, and one shock pair within these 185 SIRs. We predict a total SIR-associated shock detection rate of ∼56% at 1.5 au and compare this rate to previous findings spanning 0.1─5 au. We examine Solar Terrestrial Relations Observatory (STEREO) A data at 1 au to cross-compare with our results at 1.5 au. We determine the magnetic compression ratios (H) associated with SIRs at MAVEN and STEREO-A and find that H is ∼18% higher at 1.5 au than 1 au. We find that for a given SIR observed at both 1 and 1.5 au, H is ∼32% higher at 1.5 au. We also do not see a stark difference in the change in H for SIRs observed at both STEREO-A and MAVEN with respect to the angular separation of the spacecraft.

Keywords: Solar wind, Interplanetary physics, Corotating streams
Discovery of Weak CN Stars in the Large Magellanic Cloud and Comparison to Stellar Models. The recent discovery that red supergiants in M31 and M33 contain a weak CN spectral absorption feature at ∼8000 Å prompted us to analyze a large CTIO 4 m Hydra spectral database of stars in the Large Magellanic Cloud (LMC). We find 751 confirmed weak CN stars in the LMC, present an overview of their spectral and photometric properties, and compare them with the weak CN stars in M31 and M33. We use a method for automatically identifying weak CN stars based on a spectral template and find that weak CN stars are almost exclusively short-lived massive stars in the core He-burning evolutionary phase. We derive a mean main-sequence age of 40 Myr for these stars through a Bayesian approach to isochrone fitting that is consistent across all three galaxies. We then examine possible evolutionary processes and atmospheric conditions that could lead to weak CN stars using a suite of low-resolution model spectra. We find a preferred range of values for Teff and log g in O-rich stars that would result in the CN absorption and also speculate that this feature could arise due to the N enhancement expected in fast-rotating stars, though more targeted modeling is required.

Keywords: Carbon stars, CN stars, Red supergiant stars, Stellar evolution
Tidal Formation of Dark Matter Deficit Diffuse Galaxy NGC 1052-DF2 by SIDM. Observations have revealed a significant dark matter deficit in the ultradiffuse galaxy NGC 1052-DF2 (DF2). It is widely accepted that the formation of this unique galaxy can be attributed to the tidal stripping of its host galaxy, NGC 1052. In this study, we simulate the evolution of a satellite system containing globular clusters (GCs) within an accreting host halo in the framework of self-interacting dark matter (SIDM). Our simulation results suggest that the heightened tidal stripping resulting from dark matter (DM) self-interactions can give rise to the transformation of a conventional dwarf galaxy into a dark matter deficit galaxy resembling DF2. Furthermore, we demonstrate that a DF2 analog can also be produced on an orbit with a greater pericenter distance by increasing the strength of DM self-interactions. This suggests that the issue of extreme orbital parameters can be mitigated by implementing the SIDM model. The distributions of the GC population derived in our SIDM simulation are consistent with the observed characteristics of DF2. The potential for reproducing DF2 and its GC population in the cold dark matter scenario is also discussed.

Keywords: Dark matter