Sazuna/UAT_keywords huggingface dataset:
Universal Constants in Self-organized Criticality Systems. The occurrence frequency distributions of fluxes (F) and fluences or energies (E) observed in the majority (in 18 out of 23 cases) of astrophysical phenomena are found to be consistent with the predictions of the fractal-diffusive self-organized criticality (FD-SOC) model, which predicts power-law slopes with universal constants of αF = (9/5) = 1.80 for the flux and αE = (5/3) ≈ 1.67 for the fluence. The theoretical FD-SOC model is based on the fractal dimension, the flux-volume proportionality, and classical diffusion. The universal scaling laws predict the size distributions of numerous astrophysical phenomena, such as solar flares, stellar flares, coronal mass ejections, auroras, blazars, active galactic nuclei, black hole systems, galactic fast radio bursts, gamma-ray bursts, and soft gamma-ray repeaters. In contrast, we identify five outliers of astrophysical phenomena, i.e., coherent solar radio bursts, random solar radio bursts, solar energetic particles, cosmic rays, and pulsar glitches, which are not consistent with the standard FD-SOC model, and thus require different physical mechanisms.

Keywords: Solar flares, Magnetospheric radio emissions, Cosmic ray astronomy, Gamma-ray bursters, Galactic and extragalactic astronomy, Stellar flares, Active solar corona
Self-consistent Solutions of Evolving Nuclear Star Clusters with Two-dimensional Monte Carlo Dynamical Simulations. We recently developed a Monte Carlo method (GNC) that can simulate the dynamical evolution of a nuclear star cluster (NSC) with a massive black hole (MBH), where the two-body relaxations can be solved by the Fokker–Planck equations in energy and angular momentum space. Here we make a major update of GNC by integrating stellar potential and adiabatic invariant theory, so that we can study the self-consistent dynamics of NSCs with increasing mass of the MBH. We perform tests of the self-adaptation of cluster density due to MBH mass growth and Plummer core collapse, both finding consistent results with previous studies, the latter having a core collapse time of ∼17trh by GNC, where trh is the time of half-mass relaxation. We use GNC to study the cosmological evolution of the properties of NSCs and the mass of MBHs assuming that the mass growth of the MBH is due to loss-cone accretion of stars (e.g., tidal disruption of stars) and stellar black holes, and we compare the simulation results with the observations of NSCs in the Milky Way or nearby galaxies. It is possible for such a scenario to produce MBHs with mass 105–107 M⊙ for NSCs with stellar mass of 106–109 M⊙. In the Milky Way's NSC, to grow an MBH up to 4 × 106 M⊙, its size needs to be ∼1.7 times more compact in early Universe than the current value. MBHs with current masses &gt;6 × 107 M⊙ seem difficult to explain by loss-cone accretion alone, and thus they may require other additional accretion channels, such as gas accretion.

Keywords: Supermassive black holes, Galactic center, Gravitation, Tidal disruption, Stellar dynamics, Galaxy nuclei, Star clusters
Extragalactic Magnetar Giant Flares: Population Implications, Rates, and Prospects for Gamma-Rays, Gravitational Waves, and Neutrinos. Magnetar giant flares (MGFs) are the most energetic non-catastrophic transients known to originate from stellar objects. The first discovered events were nearby. In recent years, several extragalactic events have been identified, implying an extremely high volumetric rate. We show that future instruments with a sensitivity ≲5 × 10‑9 erg cm‑2 at ∼1 MeV will be dominated by extragalactic MGFs over short gamma-ray bursts (sGRBs). Clear discrimination of MGFs requires intrinsic GRB localization capability to identify host galaxies. As MGFs involve a release of a sizable fraction of the neutron star's magnetic free energy reservoir in a single event, they provide us with invaluable tools for better understanding magnetar birth properties and the evolution of their magnetic fields. A major obstacle is to identify a (currently) small subpopulation of MGFs in a larger sample of more energetic and distant sGRBs. We develop the tools to analyze the properties of detected events and their occurrence rate relative to sGRBs. Even with the current (limited) number of events, we can constrain the initial internal magnetic field of a typical magnetar at formation to be B0 ≈ 4 × 1014–2 × 1015 G. Larger samples will constrain the distribution of birth fields. We also estimate the contribution of MGFs to the gravitational-wave (GW) stochastic background. Depending on the acceleration time of baryon-loaded ejecta involved in MGFs, their GW emission may reach beyond 10 kHz and, if so, will likely dominate over other conventional astrophysical sources in that frequency range.

Keywords: Magnetars, Neutrino astronomy, Gamma-ray bursts, Gravitational wave sources
Bridging the Gap: GRB 230812B—A 3 s Supernova-associated Burst Detected by the GRID Mission. GRB 230812B, detected by the Gamma-Ray Integrated Detectors constellation mission, is an exceptionally bright gamma-ray burst (GRB) with a duration of only 3 s. Sitting near the traditional boundary (∼2 s) between long and short GRBs, GRB 230812B is notably associated with a supernova, indicating a massive star progenitor. This makes it a rare example of a short-duration GRB resulting from stellar collapse. Our analysis, using a time-evolving synchrotron model, suggests that the burst has an emission radius of approximately 1014.5 cm. We propose that the short duration of GRB 230812B is due to the combined effects of the central engine's activity time and the time required for the jet to break through the stellar envelope. Our findings provide another case that challenges the conventional view that short-duration GRBs originate exclusively from compact object mergers, demonstrating that a broader range of durations exists for GRBs arising from the collapse of massive stars.

Keywords: Gamma-ray bursters, Supernovae
Hunting for Candidates of Changing-look Blazars Using Mclust Clustering Analysis. Changing-look blazars (CLBs) are blazars whose optical spectral lines at different epochs show significant changes and present a clear transition between standard FSRQ and BL Lacertae (BL Lac). Changing-look phenomena in blazars are highly significant for enhancing our understanding of certain physical problems of active galactic nuclei (AGNs), such as the potential mechanism of state transition in the accretion process of supermassive black holes in the central engine of AGNs, the possible intrinsic variation of the jet, and the connection between the accretion disk and the jet. Currently, the CLBs reported in the literature are still rare astronomical objects. In our previous work, we found that there are eight physical property parameters of CLBs located between those of FSRQs and BL Lacs. In order to search for more CLB candidates (CLBCs), we employed the mclust Gaussian mixture modeling clustering algorithm to perform clustering analysis for 255 subsets of the eight physical property parameters with 2250 blazars from 4FGL data release 3. We find that there are 29 subsets with three groups (corresponding to bl lacs, fsrqs, and CLBCs), in which there are four subsets with an adjusted Rand index greater than 0.610. The combined clustering results from the four subsets report that there are 111 CLBCs, which include 44 CLBs reported in previous literature and 67 new CLBCs, of which 11 are labeled as BL Lacs and 56 are labeled as FSRQs in the 4FGL catalog.

Keywords: Blazars, Flat-spectrum radio quasars, Active galactic nuclei, BL Lacertae objects
Multiband Polarization Profile Analysis of Three-component Radio Pulsars by Implementing a Relativistic Phase-shift Method. In this paper, we show the estimation of the emission altitude of pulsars PSRs B0329+54, B0450-18, B2045-16, J1909+0007, and J0337+1715 for both core and conal components at multiple radio bands by implementing a relativistic phase-shift method, which is constrained based on the plethora of standard radio emission geometry. Using the information of pulse longitudes for each component, coupled with a dipolar field geometry, we obtain a rough estimation of the height and transverse location of the emitting cones for these pulsars, i.e., footpoint location of the pulse edge, normalized with the last open magnetic field line constant. We also analyzed the profile of a well-known millisecond pulsar J0337+1715 at 1250 MHz, which has an asymmetric core-cone structure for both the main pulse and interpulse. This is the first time such a case has been analyzed to probe emission height by implementing the relativistic phase-shift method. We discuss the implications of our findings in the context of the pulsar's emission geometry to reach a consensus on the existing emission mechanism of pulsars.

Keywords: Radio pulsars
The Morphology of Dwarf Galaxies Hosting Variable Active Galactic Nuclei. We analyze Hubble Space Telescope optical imaging of eight low-mass galaxies hosting active galactic nuclei (AGN) identified via their photometric variability in V. F. Baldassare et al. We use GALFIT to model the 2D galaxy light profiles, and find a diversity of morphologies. The galaxies with regular morphologies are best fit with pseudobulges and disks, rather than classical bulges. We estimate black hole masses using scaling relations and find black hole masses of 103.7‑6.6 M⊙. We compare this sample to dwarf galaxies with AGN selected via optical spectroscopy. On average, the variable host galaxies have lower-mass black holes. We analyze the brightest point source in each galaxy and find their properties are not entirely consistent with star clusters, indicating that they are likely AGN. These point sources are found to have lower luminosities than spectroscopically selected dwarf AGN, but brighter than the point sources in dwarf galaxies not identified as AGN. Our detailed imaging analysis shows that variability selection has the potential to find lower-mass black holes and lower-luminosity AGN than optical spectroscopy. These active dwarfs may have been missed by spectroscopic searches due to star formation dilution or low gas content.

Keywords: AGN host galaxies, Dwarf galaxies, Active galactic nuclei
Measuring Star Formation Rates in the Milky Way from Hi-GAL 70 μm Observations. Three methods for computing the total star formation rate (SFR) of the Milky Way agree well with a reference value of 1.65 ± 0.19 M⊙ yr−1. They are then used to determine the radial dependence of the SFR and face-on map for the Milky Way. First, the method based on a model of star formation in Hi-GAL-defined dense clumps, adjusted for an increase in the gas-to-dust ratio with Galactocentric radius, predicts 1.65 ± 0.61 M⊙ yr−1. Second, the method using the 70 μm emission, commonly used in other galaxies, with a technique to assign distances to the extended emission, predicts  1.42−0.44+0.63  M⊙ yr−1. Finally, a method based on theoretical predictions of star formation efficiency as a function of virial parameter, with masses corrected for metallicity dependence, applied to a catalog of molecular clouds also predicts a value in agreement at 1.47 M⊙ yr−1. The three methods predict the radial variation of the SFR, with remarkably good agreement from the Central Molecular Zone out to about 20 kpc. More differences were seen in face-on maps with a resolution of 0.5 kpc made with the three approaches and in comparisons to the local (within 3 kpc) SFR, indicating limitations of the methods when applied to smaller scales. The 70 μm SFR follows very closely the surface density of molecular gas, corrected for a metallicity-dependent CO conversion factor. A molecular gas depletion time of 1 Gyr is consistent with the data, as is a molecular Kennicutt─Schmidt relation with a power-law slope of 1.10 ± 0.06.

Keywords: Gas-to-dust ratio, Far infrared astronomy, Star formation, Interstellar medium, Milky Way Galaxy
Asteroseismology with TESS: Emergence of Dipole Mode Suppression from Subgiants?. Dipole mode suppression is an observed behavior of solar-like oscillations in evolved stars. This study aims to search for depressed dipole modes in giant stars using data from the Transiting Exoplanet Survey Satellite (TESS) and investigate when the suppression starts to emerge. We study a sample of 8651 evolved stars from TESS and find 179 stars with significant dipole mode depression by comparing the oscillation amplitudes of radial and dipole modes. Notably, 11 of them are located near the base of the red giant branch, indicating that mode suppression appears earlier than the point inferred in previous studies with Kepler data. These findings provide new evidence for dipole mode suppression in giant stars, particularly in subgiants.

Keywords: Stellar magnetic fields, Subgiant stars, Asteroseismology, Giant stars
Dependence of Multiband Absolute Magnitudes and Color Indexes of the Tip of the Red Giant Branch Stars on Metallicity in Galactic Globular Clusters. The tip of the red giant branch (TRGB) stars have attracted intensive attention in recent years because their I-band absolute magnitudes, MI, are often used for distance calibration in the Hubble constant measurements because of its almost independence on metallicity ([Fe/H]). However, a discrepancy exists between various studies, and the theoretical stellar model predicts the dependence of their luminosity on [Fe/H]. Here, we present a careful study of the dependence of absolute magnitudes and color indexes on metallicity in optical and near-infrared bands. With the TRGB stars identified in 33 Galactic globular clusters by the reddest color in the GBP ‑ GRP versus GRP diagram, it is confirmed that MI is almost constant of ‑4.017 ± 0.036 ± 0.027 mag when [Fe/H] &lt; ‑1.2, which would give H0 = 70.86 ± 1.2 ± 0.9 km s‑1 Mpc‑1 with this updated luminosity calibration for Type Ia supernovae. However, for [Fe/H] &gt; ‑1.2, MI is found to become fainter with lower metallicity, which would lead to a larger Hubble constant. In the optical GBP, GRP, and V bands, the absolute magnitude of TRGB stars tends to increase with metallicity, while in the infrared J, H, and Ks bands, the variation with metallicity shows an inverse tendency. In addition, the analytical relations of the color indexes with metallicity are presented, which have smaller dispersion than those derived for the corresponding absolute magnitudes.

Keywords: Globular star clusters, Red giant tip, Red giant branch
The Bolometric Light-curve Modeling of 98 Type I Superluminous Supernovae Using the Magnetar- and the Circumstellar Interaction Models Reveals Surprisingly High Ejecta Masses. We present the bolometric light-curve modeling of 98 hydrogen-poor superluminous supernovae (SLSNe-I) using three types of power inputs: the magnetar model and two kinds of circumstellar interaction models, applying the constant density and the steady wind scenario. The quasi-bolometric luminosities of the objects were calculated from the Zwicky Transient Facility g- and r-band data using the methodology of Chen et al., and then they were modeled with the Minim code. It was found that the light curves of 45 SLSNe-I can be fitted equally well with both the magnetar and the circumstellar material (CSM) models, 14 objects prefer the magnetar model, and 39 SLSNe-I favor the CSM model. The magnetar modeling yielded a mean spin period of P = 4.1 ± 0.20 ms and a magnetic field of B = 5.65 ± 0.43 · 1014 G, consistent with the literature. However, the ejected mass was estimated to be significantly larger compared to previous studies presenting either multicolor light-curve modeling with MOSFiT or bolometric light-curve modeling: we obtained a mean value and standard error of 34.26 and 4.67 M⊙, respectively. The circumstellar interaction models resulted in even larger ejecta masses with a mean and standard error of 116.82 and 5.97 M⊙ for the constant density model, and 105.99 and 4.50 M⊙ for the steady wind model. Although the ejected mass depends strongly on the electron scattering opacity (assumed to be κ = 0.2 in this work) and the ejecta velocity, which were estimated to be globally larger compared to earlier studies, our results suggest that SLSNe-I are indeed explosions of the most-massive stars.

Keywords: Burst astrophysics, Supernovae
Constraining the Nuclear Equation of State of a Neutron Star via High-frequency Quasi-periodic Oscillation in Short Gamma-Ray Bursts. The determination of the equation of state (EOS) of a neutron star (NS) and its maximum mass is very important for understanding the formation and properties of NSs under extreme conditions, but they remain open questions. Short-duration gamma-ray bursts (GRBs) are believed to originate from the merger of binary NSs or giant flares (GFs) of soft gamma repeaters (SGRs). Recently, the high-frequency quasi-periodic oscillations (QPOs) have been claimed to be identified from two short GRBs (GRB 931101B and GRB 910711). In this paper, we propose that the observed high-frequency QPOs in these two short GRBs result from torsional oscillations in the GFs of SGRs associated with cold NSs, or from radial oscillations of hypermassive NSs as the hot remnants of binary NS mergers, and then to constrain the EOS of NSs. For torsional oscillations, the six selected EOSs (TM1, NL3, APR, SLy4, DDME2, and GM1) of NSs suitable for the zero-temperature condition exhibit significant overlap in mass ranges, suggesting that we cannot constrain the EOS of NSs. For radial oscillations, the six selected EOSs (IUF, TM1, TMA, FSG, BHBLp, and NL3) of NSs suitable for the high-temperature condition cannot be ruled out when redshift is considered. However, it is found that the EOS can only be constrained if the redshift and temperature of the remnant can be measured.

Keywords: Gamma-ray bursts
Impacts of UV Radiation from an AGN on Planetary Atmospheres and Consequences for Galactic Habitability. We present a study of the effects of ultraviolet (UV) emission from active galactic nuclei (AGN) on the atmospheric composition of planets and potential impact on life. It is expected that all supermassive black holes, which reside at galactic centers, have gone through periods of high AGN activity in order to reach their current masses. We examine potential damaging effects on lifeforms on planets with different atmosphere types and receiving different levels of AGN flux, using data on the sensitivity of various species' cells to UV radiation to determine when radiation becomes "dangerous." We also consider potential chemical changes to planetary atmospheres as a result of UV radiation from AGN, using the Platform for Atmosphere, Land, Earth, and Ocean photochemical model. We find that the presence of sufficient initial oxygen (surface mixing ratio ≥10‑3 mol mol‑1) in the planet's atmosphere allows a thicker ozone layer to form in response to AGN radiation, which reduces the level of dangerous UV radiation incident on the planetary surface from what it was in absence of an AGN. We estimate the fraction of solar systems in galaxies that would be affected by substantial AGN UV radiation, and find that the impact is most pronounced in compact galaxies such as "red nugget relics," as compared to typical present-day ellipticals and spirals (using M87 and the Milky Way as examples).

Keywords: Active galactic nuclei, Habitable planets, Exoplanet atmospheres, Black holes
Alfvén Wave Conversion to Low Frequency Fast Magnetosonic Waves in Magnetar Magnetospheres. Rapid shear motion of magnetar crust can launch Alfvén waves into the magnetosphere. The dissipation of the Alfvén waves has been theorized to power the X-ray bursts characteristic of magnetars. However, the process by which Alfvén waves convert their energy to X-rays is unclear. Recent work has suggested that energetic fast magnetosonic (fast) waves can be produced as a byproduct of Alfvén waves propagating on curved magnetic field lines; their subsequent dissipation may power X-ray bursts. In this work, we investigate the production of fast waves by performing axisymmetric force-free simulations of Alfvén waves propagating in a dipolar magnetosphere. For Alfvén wave trains that do not completely fill the flux tube confining them, we find a fast wave dominated by a low frequency component with a wavelength defined by the bouncing time of the Alfvén waves. In contrast, when the wave train is long enough to completely fill the flux tube, and the Alfvén waves overlap significantly, the energy is quickly converted into a fast wave with a higher frequency that corresponds to twice the Alfvén wave frequency. We investigate how the energy, duration, and wavelength of the initial Alfvén wave train affect the conversion efficiency to fast waves. For modestly energetic star quakes, we see that the fast waves that are produced will become nonlinear well within the magnetosphere, and we comment on the X-ray emission that one may expect from such events.

Keywords: Neutron stars, Magnetars, Alfven waves, Plasma physics
A Pilot Study for the CSST Slitless Spectroscopic Quasar Survey Based on Mock Data. The wide survey of the Chinese Space Station Telescope (CSST) will observe a large field of 17,500 deg2. The GU, GV, and GI grism observations of CSST will cover the wavelength range from 2550 to 10000 Å at a resolution of R ∼ 200 and a depth of about 22 AB magnitude for the continuum. In this paper, we present a pipeline to identify quasars and measure their physical properties with the CSST mock data. We simulate the raw images and extract the one-dimensional grism spectra for quasars, galaxies, and stars with r-band magnitudes of 18 &lt; mr &lt; 22 using the CSST Cycle 6 simulation code (https://csst-tb.bao.ac.cn/code/csst_sim/csst-simulation). Using a convolution neural network, we separate quasars from stars and galaxies. We measure the redshifts by identifying strong emission lines of quasars. We also fit the 1D slitless spectra with QSOFITMORE to estimate black hole masses and Eddington ratios. Our results show that CSST slitless spectroscopy can effectively separate quasars with redshifts z = 0‑5 from other types of objects with an accuracy of 99%. Among those successfully classified quasars, 90% of them could have precise redshift measurements with σNMAD = 0.002. The scatters of black hole masses and Eddington ratios from the spectral fittings are 0.13 and 0.15 dex, respectively. The metallicity diagnosis line ratios have a scatter of 0.1–0.2 dex. Our results show that the CSST slitless spectroscopy survey has the potential to discover about 0.9 million new quasars and provide important contributions to the science of active galactic nuclei and cosmology.

Keywords: Supermassive black holes, Quasars, Galactic and extragalactic astronomy, Active galactic nuclei, Spectroscopy
Exploring Mass Transfer Mechanisms in Symbiotic Systems. We define two regimes of the parameter space of symbiotic systems based on the dominant mass transfer mechanism. A wide range of white dwarf (WD) mass, donor mass, and donor radius combinations are explored to determine the separation for each parameter combination, below which wind Roche-lobe (RL) overflow will be the dominant mass transfer mechanism. The underlying concept is the premise that the wind accelerates. If it reaches the RL before attaining sufficient velocity to escape, it will be trapped and gravitationally focused through the inner Lagrangian point toward the accreting WD. However, if the wind succeeds in attaining the required velocity to escape from the donor's RL, it will disperse isotropically, and the dominant mass transfer mechanism will be the Bondi–Hoyle–Lyttleton prescription, in which only a fraction of the wind will be accreted onto the WD. We present these two regimes of the 4D parameter space, covering 375 different parameter combinations.

Keywords: Binary stars, Interacting binary stars, Symbiotic novae, Stellar accretion, Symbiotic binary stars