Sazuna/UAT_keywords huggingface dataset:
Periodic Gamma-Ray Modulation of the Blazar PG 1553+113 Confirmed by Fermi-LAT and Multiwavelength Observations. A 2.1 yr periodic oscillation of the gamma-ray flux from the blazar PG 1553+113 has previously been tentatively identified in ∼7 yr of data from the Fermi Large Area Telescope. After 15 yr of Fermi sky-survey observations, doubling the total time range, we report &gt;7 cycle gamma-ray modulation with an estimated significance of 4σ against stochastic red noise. Independent determinations of oscillation period and phase in the earlier and the new data are in close agreement (chance probability &lt;0.01). Pulse timing over the full light curve is also consistent with a coherent periodicity. Multiwavelength new data from Swift X-Ray Telescope, Burst Alert Telescope, and UVOT, and from KAIT, Catalina Sky Survey, All-Sky Automated Survey for Supernovae, and Owens Valley Radio Observatory ground-based observatories as well as archival Rossi X-Ray Timing Explorer satellite-All Sky Monitor data, published optical data of Tuorla, and optical historical Harvard plates data are included in our work. Optical and radio light curves show clear correlations with the gamma-ray modulation, possibly with a nonconstant time lag for the radio flux. We interpret the gamma-ray periodicity as possibly arising from a pulsational accretion flow in a sub-parsec binary supermassive black hole system of elevated mass ratio, with orbital modulation of the supplied material and energy in the jet. Other astrophysical scenarios introduced include instabilities, disk and jet precession, rotation or nutation, and perturbations by massive stars or intermediate-mass black holes in polar orbit.

Keywords: Supermassive black holes, BL Lacertae objects, Jets, High energy astrophysics, Gamma-ray sources, Blazars, Relativistic jets, Galaxy accretion disks, Gamma-ray telescopes, Active galactic nuclei, Gamma-ray astronomy, Gamma-rays
Spectropolarimetric Inversion in Four Dimensions with Deep Learning (SPIn4D). I. Overview, Magnetohydrodynamic Modeling, and Stokes Profile Synthesis. The National Science Foundation's Daniel K. Inouye Solar Telescope (DKIST) will provide high-resolution, multiline spectropolarimetric observations that are poised to revolutionize our understanding of the Sun. Given the massive data volume, novel inference techniques are required to unlock its full potential. Here, we provide an overview of our "SPIn4D" project, which aims to develop deep convolutional neural networks (CNNs) for estimating the physical properties of the solar photosphere from DKIST spectropolarimetric observations. We describe the magnetohydrodynamic (MHD) modeling and the Stokes profile synthesis pipeline that produce the simulated output and input data, respectively. These data will be used to train a set of CNNs that can rapidly infer the four-dimensional MHD state vectors by exploiting the spatiotemporally coherent patterns in the Stokes profile time series. Specifically, our radiative MHD model simulates the small-scale dynamo actions that are prevalent in quiet-Sun and plage regions. Six cases with different mean magnetic fields have been explored; each case covers six solar-hours, totaling 109 TB in data volume. The simulation domain covers at least 25 × 25 × 8 Mm, with 16 × 16 × 12 km spatial resolution, extending from the upper convection zone up to the temperature minimum region. The outputs are stored at a 40 s cadence. We forward model the Stokes profile of two sets of Fe I lines at 630 and 1565 nm, which will be simultaneously observed by DKIST and can better constrain the parameter variations along the line of sight. The MHD model output and the synthetic Stokes profiles are publicly available, with 13.7 TB in the initial release.

Keywords: Spectropolarimetry, Solar photosphere, Convolutional neural networks, Magnetic fields, Active solar chromosphere, Magnetohydrodynamical simulations
DIISC-IV. DIISCovery of Anomalously Low Metallicity H II Regions in NGC 99: Indirect Evidence of Gas Inflows. As a part of the Deciphering the Interplay between the Interstellar medium, Stars, and the Circumgalactic medium (DIISC) survey, we investigate indirect evidence of gas inflow into the disk of the galaxy NGC 99. We combine optical spectra from the Binospec spectrograph on the MMT telescope with optical imaging data from the Vatican Advanced Technology Telescope, radio H I 21 cm emission images from the NSF Karl G. Jansky's Very Large Array, and UV spectroscopy from the Cosmic Origins Spectrograph on the Hubble Space Telescope. We measure emission lines (Hα, Hβ, [O III]λ5007, [N II]λ6583, and [S II]λ6717, 31) in 26 H II regions scattered about the galaxy and estimate a radial metallicity gradient of ‑0.017 dex kpc‑1 using the N2 metallicity indicator. Two regions in the sample exhibit an anomalously low metallicity (ALM) of 12 + log(O/H) = 8.36 dex, which is ∼0.16 dex lower than other regions at that galactocentric radius. They also show a high difference between their H I and Hα line of sight velocities on the order of 35 km s‑1. Chemical evolution modeling indicates gas accretion as the cause of the ALM regions. We find evidence for corotation between the interstellar medium of NGC 99 and Lyα clouds in its circumgalactic medium, which suggests a possible pathway for low metallicity gas accretion. We also calculate the resolved Fundamental Metallicity Relation (rFMR) on subkiloparsec scales using localized gas-phase metallicity, stellar mass surface density, and star formation rate surface density. The rFMR shows a similar trend as that found by previous localized and global FMR relations.

Keywords: Galaxy chemical evolution, Galaxy abundances, Galaxy accretion, Circumgalactic medium, H II regions
A Promising Approach for Determining Neutrino Mass Hierarchy by Using Supernova Neutrino Detections. The determination of neutrino mass hierarchy is crucial for particle physics, astrophysics, and cosmology. In this work, we propose an easy-to-use method to determine the neutrino hierarchy based on core-collapse supernova (CCSN) neutrino detections. By analyzing the expected event rates of the neutrino burst at a terrestrial water Cherenkov detector, we found that the event rates predicted by the normal and inverted hierarchy models have marked differences in the neutrino energy range 10 ∼ 20 MeV and the postbounce time &lt;0.5 s. Within this specific energy and time range, the analytical relationship between the cumulative event number and proto–neutron star (PNS) baryon mass is extracted. Based on the normal and inverted hierarchy models, two different PNS masses can be inferred from this relationship by using the time profile of neutrino events. Then, the neutrino hierarchy can be determined by comparing the PNS mass inferred from the neutrino detections and the electromagnetic or gravitational-wave channels. Furthermore, the nonadiabatic part of the Mikheyev–Smirnov–Wolfenstein flavor conversions may also be quantified with this method, which would be very helpful for the studies of the explosion mechanism and nucleosynthesis of CCSNe.

Keywords: Neutrino oscillations, Neutron stars, Supernova neutrinos, Neutrino masses
Simultaneous Eruption and Shrinkage of Preexisting Flare Loops during a Subsequent Solar Eruption. We investigated two consecutive solar eruption events in the solar active region 12994 at the solar eastern limb on 2022 April 15. We found that the flare loops formed by the first eruption were involved in the second eruption. During the initial stage of the second flare, the middle part of these flare loops (E-loops) erupted outward along with the flux ropes below, while the parts of the flare loops (I-loops1 and I-loops2) on either side of the E-loops first rose and then contracted. Approximately 1 hr after the eruption, the heights of I-loops1 and I-loops2 decreased by 9 Mm and 45 Mm, respectively, compared to before the eruption. Their maximum descent velocities were 30 km s‑1 and 130 km s‑1, respectively. The differential emission measure results indicate that the plasma above I-loops1 and I-loops2 began to be heated about 23 minutes and 44 minutes after the start of the second flare, respectively. Within ∼20 minutes, the plasma temperature in these regions increased from ∼3 MK to ∼6 MK. We proposed an adiabatic heating mechanism where magnetic energy would be converted into thermal and kinetic energy when the prestretched loops contract. Our calculations show that the magnetic energy required to heat the two high-temperature regions are 1029–1030 erg, which correspond to a loss of field strength of 2–3 G.

Keywords: Solar activity, Solar flares
Model-independent Calibration for Sound Horizon: Combining Observations of Supernovae and Baryon Acoustic Oscillation Measurements. The sound horizon scale is a key theoretical prediction of the cosmological model that depends on the speed of sound in the baryon-photon fluid and the rate of expansion of the early Universe, before matter and radiation decoupled. Baryon acoustic oscillations (BAOs) offer the direct measurement of this important scale imprinted in the distribution of galaxies. We propose a new model-independent method to calibrate the sound horizon   (relative standard ruler) by using the latest observations of Type Ia supernovae (SNe Ia) and 2D BAO measurements. The final result is   Mpc h ‑1 in the framework of the Pantheon SN Ia data set. This result changes to   Mpc h ‑1 when the Pantheon+ data set is used. To highlight our analysis and results, we also use BAO DESI measurements and obtain the best-fitting value   Mpc h ‑1. Note that even without an estimate of the dimensionless Hubble constant h, the combination of 2D BAO and SN Ia data sets already constrains the low-redshift standard ruler scale   at the ∼1.26% level (at the ∼1.00% level in the framework of BAO DESI data set). More importantly, it is interesting to note that most of the   obtained at high redshifts have systematically larger values: 9 out of 15 results are larger than the result obtained by combining all 2D BAOs. This finding may give us a better understanding of the discordance between the data sets, shed light on the Hubble tension, or reveal the need for new physics beyond the standard cosmological model.

Keywords: Cosmology, Baryon acoustic oscillations, Gaussian Processes regression
Slope of Magnetic Field–Density Relation as an Indicator of Magnetic Dominance. The electromagnetic field is a fundamental force in nature that regulates the formation of stars in the Universe. Despite decades of efforts, a reliable assessment of the importance of the magnetic fields in star formation relations remains missing. In star formation research, our acknowledgment of the importance of magnetic fields is best summarized by the R. M. Crutcher et al. B–ρ relation,  &lt;?CDATA \begin{eqnarray*}\mathrm{log}B(\rho )/\mathrm{Gauss}=\left\{\begin{array}{l}-5,\,\mathrm{if}\,\rho \,\lesssim \,{10}^{-20}\,{\rm{g}}\,{\mathrm{cm}}^{-3}\\ \displaystyle \frac{2}{3}\cdot \mathrm{log}\rho +\mathrm{log}{\rho }_{0},\,\mathrm{if}\,\rho \,\gtrsim \,{10}^{-20}\,{\rm{g}}\,{\mathrm{cm}}^{-3},\end{array}\right.\end{eqnarray*}?&gt;  whose interpretation remains controversial. The relation is either interpreted as proof of the importance of a magnetic field in gravitational collapse or as the result of self-similar collapse where the role of the magnetic field is secondary to gravity. Using simulations, we find a fundamental relation,  –k  B‑ρ  (the slope of the B–ρ relation):  &lt;?CDATA \begin{eqnarray*}\displaystyle \frac{{{ \mathcal M }}_{{\rm{A}}}}{{{ \mathcal M }}_{{\rm{A}},{\rm{c}}}}={{\rm{k}}}_{B-\rho }^{{ \mathcal K }}\approx \displaystyle \frac{{{ \mathcal M }}_{{\rm{A}}}}{7.5}\approx {{\rm{k}}}_{B-\rho }^{1.7\pm 0.15}.\end{eqnarray*}?&gt;  This fundamental B–ρ slope relation enables one to measure the Alfvénic Mach number, a direct indicator of the importance of the magnetic field, using the distribution of data in the B–ρ plane. It allows us to apply the following empirical B–ρ relation:  &lt;?CDATA \begin{eqnarray*}\displaystyle \frac{B}{{B}_{c}}=\exp \left({\left(\displaystyle \frac{\gamma }{{ \mathcal K }}\right)}^{-1}{\left(\displaystyle \frac{\rho }{{\rho }_{c}}\right)}^{\displaystyle \frac{\gamma }{{ \mathcal K }}}\right)\approx \displaystyle \frac{B}{{10}^{-6.3}{\rm{G}}}\approx \exp \left(9{\left(\displaystyle \frac{\rho }{{10}^{-16.1}{\rm{g}}\,{\mathrm{cm}}^{-3}}\right)}^{0.11}\right)\ ,\end{eqnarray*}?&gt;  which offers an excellent fit to the Crutcher et al. data, where we assume an   relation ( ). The foundational   relation provides an independent way to measure the importance of the magnetic field against the kinematic motion using multiple magnetic-field measurements. Our approach offers a new interpretation of the classical B–ρ relation, where a gradual decrease in the importance of B at higher densities is implied.

Keywords: Interstellar magnetic fields, Star formation, Interstellar medium
Orbital-period Changes of Low-mass X-Ray Binaries Driven by Magnetic Braking. Magnetic braking (MB) plays an important role in driving the evolution of low-mass X-ray binaries (LMXBs). The modified MB prescription, the convection and rotation boosted (CARB) model, is very successful in reproducing the detected mass-transfer rates of persistent neutron star (NS) LMXBs. In this work, we investigate whether the CARB MB prescription could account for the formation and evolution of some NS and black hole (BH) LMXBs with an observed orbital-period derivative. Using the MESA code, we perform a detailed binary evolution model for six NS and three BH LMXBs. Our simulations find that the CARB MB prescription can successfully reproduce the observed donor-star masses, orbital periods, and period derivatives of four NS LMXBs and one BH LMXB. Our calculated effective temperatures are in good agreement with the detected spectral types of two NS LMXBs and one BH LMXB. However, the standard MB model makes it difficult to produce the observed period derivatives of those LMXBs experiencing a rapid orbital shrinkage or expansion.

Keywords: Neutron stars, X-ray binary stars, Black holes, Orbital evolution, Stellar evolution
The Disk Reverberation Mapping of the Lensed Quasar Q0957+561. The measurement of continuum time lags in lensed quasars can effectively probe the accretion physics of quasars. This is because microlensing observations of lensed quasars can provide constraints on the half-light radii of quasar accretion disks. By combining the microlensing results with time lag measurements, one can, for the first time, estimate the propagation velocity of the physical process that drives interband time lags and cross correlations among disk emission (i.e., in UV/optical bands). In this study, we perform the disk reverberation mapping study for the well-studied lensed quasar, Q0957+561. The cross correlation between the Zwicky Transient Facility g and r bands was measured; the g variations lead the r ones by 6.4 ± 2.6 days in the rest frame. In combination with the half-light radius from the existing literature, we find that the propagation velocity of the variability mechanism should be   times the speed of light. We discuss the possible outcomes of this result. Similar studies can be applied to other lensed quasars by utilizing the Legacy Survey of Space and Time observations.

Keywords: Accretion, Supermassive black holes, Reverberation mapping, Quasar microlensing
Characterizing the Nanohertz Gravitational Wave Background Using a t-process Power Spectral Density. Pulsar timing arrays (PTAs) are sensitive to low-frequency gravitational waves (GWs), which induce correlated changes in millisecond pulsars' timing residuals. PTA collaborations around the world have recently announced evidence of a nanohertz gravitational wave background (GWB), which may be produced by a population of supermassive black hole binaries (SMBHBs). The GWB is often modeled as following a power-law power spectral density (PSD); however, a GWB produced by a cosmological population of SMBHBs is expected to have a more complex power spectrum due to the discrete nature of the sources. In this paper, we investigate using a t-process PSD to model the GWB, which allows us to fit for both the underlying power-law amplitude and spectral index as well as deviations from that power law, which may be produced by individual nearby binaries. We create simulated data sets based on the properties of the NANOGrav 15 yr data set, and we demonstrate that the t-process PSD can accurately recover the PSD when deviations from a power law are present. With longer timed data sets and more pulsars, we expect the sensitivity of our PTAs to improve, which will allow us to precisely measure the PSD of the GWB and study the sources producing it.

Keywords: Gravitation, Computational methods, Gravitational wave astronomy, Markov chain Monte Carlo
SN 1885A and Supernova Remnants in the Centre of M31 with LOFAR. We present the first LOFAR image of the center of M31 at a frequency of 150 MHz. We clearly detect three supernova remnants, which, along with archival VLA data at 3 GHz and other published radio and X-ray data, allows us to characterize them in detail. Our observations also allow us to obtain upper limits of the historical SN 1885A, which is undetected even at a low frequency of 150 MHz. From analytical modeling, we find that SN 1885A will stay in its free-expansion phase for at least another couple of centuries. We find an upper limit of n H ≲ 0.04 cm‑3 for the interstellar medium of SN 1885A, and that the SN ejecta density is not shallower than ∝r ‑9 (on average). From the 2.6σ tentative detection in X-ray, our analysis shows that nonthermal emission is expected to dominate the SN 1885A emission. Comparing our results with those on G1.9+0.3, we find that it is likely that the asymmetries in G1.9+0.3 make it a more efficient radio and X-ray emitter than SN 1885A. For Braun 80, 95, and 101, the other remnants in this region, we estimate ages of 5200, 8100, and 13,100 yr, and shock speeds of 1150, 880, and 660 km s‑1, respectively. Based on this, the supernova rate in the central 0.5 kpc × 0.6 kpc of M31 is at least one per ∼3000 yr. We estimate radio spectral indices of ‑0.66 ± 0.05, ‑0.37 ± 0.03, and ‑0.50 ± 0.03 for the remnants, respectively, which match fairly well with previous studies.

Keywords: Radio continuum emission, Supernova remnants, Galaxies
Broadband Spectral Modeling of the M87 Nucleus. We study spectra produced by weakly accreting black hole (BH) systems using the semianalytic advection-dominated accretion flow (ADAF) model and the general-relativistic magnetohydrodynamic (GRMHD) simulation. We find significant differences between these two approaches related to a wider spread of the flow parameters as well as a much steeper radial distribution of the magnetic field in the latter. We apply these spectral models to the broadband spectral energy distribution (SED) of the nucleus of the M87 galaxy. The standard (in particular, 1D) formulation of the ADAF model does not allow us to explain it; previous claims that this model reproduces the observed SED suffer from an inaccurate treatment of the Compton process. The spectra based on GRMHD simulation are in a much better agreement with the observed data. In our GRMHD model, in which we assumed the BH spin a = 0.9, the bulk of radiation observed between the millimeter and the X-ray range is produced in the disk area within 4 gravitational radii from the BH. In this solution, the synchrotron component easily reproduces the spectral data between the millimeter and the UV range, and the Compton component does not violate the X-rays constraints, for   yr‑1 and a relatively strong magnetic field, with the plasma β ∼ 1 in the region where radiation is produced. However, the Compton component cannot explain the observed X-ray spectrum. Instead, the X-ray spectrum can be reproduced by a high-energy tail of the synchrotron spectrum if electrons have a hybrid energy distribution with a ∼5% nonthermal component.

Keywords: Accretion, Active galactic nuclei, Astrophysical black holes
Low-latitude Magnetic Flux Emergence on Rapidly Rotating Solar-type Stars. Besides a dense coverage of their high latitudes by starspots, rapidly rotating cool stars also display low-latitude spots in Doppler images, although generally with lower coverage. In contrast, flux emergence models of fast-rotating stars predict strong poleward deflection of radially rising magnetic flux as the Coriolis effect dominates over buoyancy, leaving a spot-free band around the equator. To resolve this discrepancy, we consider a flux tube near the base of the convection zone in a solar-type star rotating 8 times faster than the Sun, assuming field intensification by weak-tube explosions. For the intensification to continue into the buoyancy-dominated regime, the upper convection zone must have a significantly steeper temperature gradient than in the Sun by a factor that is comparable with that found in 3D simulations of rotating convection. Within the hypothesis that stellar active regions stem from the base of the convection zone, flux emergence between the equator and 20° latitudes requires highly supercritical field strengths of up to 500 kG in rapidly rotating stars. These field strengths require explosions of 100 kG tubes within the convection zone, compatible with reasonable values of the superadiabatic temperature gradient associated with the more rapid rotation.

Keywords: Starspots, Solar magnetic flux emergence, Solar analogs, G dwarf stars, Stellar magnetic fields, Stellar activity
Radio Continuum Halos of Seven Nearby Large Galaxies Using uGMRT. We present the results of deep radio observations of seven nearby large galaxies observed using the upgraded Giant Metrewave Radio Telescope (uGMRT) 0.3–0.5 GHz receivers with an angular resolution of ∼10″. The achieved sensitivities of these observations range from ≈15 to 50 μJy beam‑1, which is a factor of ≈3–4 lower than the previous observations at these frequencies. For two galaxies (NGC 3344 and NGC 3627) with moderate inclination angles, significant diffuse emissions are seen for the first time. The detected radio halos in the vertical direction are significantly larger in our 0.4 GHz maps compared to the observations at ∼1.5 GHz for four nearly edge-on galaxies—NGC 3623, NGC 4096, NGC 4594, and NGC 4631. For these four galaxies, significantly larger halos are also detected along the galaxy disk. For NGC 3623 and NGC 4594, we could detect elongated radio disks that were not seen before. We also present new uGMRT images of NGC 3344 and NGC 3623 at 1.3 GHz and a new VLA image of NGC 3627 at 1.5 GHz. We fitted an exponential function to the flux densities along different cross-cuts and found a significantly wider distribution at the 0.4 GHz uGMRT images compared to the high-frequency images at ∼1.5 GHz. Using maps at 0.144, 0.4, and ∼1.5 GHz, we made spectral index maps of the seven sample galaxies and found a steepening of the spectrum up to a value of ∼‑1.5 in the halo regions of the galaxies.

Keywords: Galaxy magnetic fields, Spiral galaxies, Interstellar medium, Radio continuum emission, Cosmic rays