Sazuna/UAT_keywords huggingface dataset:
VERITAS Discovery of Very High Energy Gamma-Ray Emission from S3 1227+25 and Multiwavelength Observations. We report the detection of very high energy gamma-ray emission from the blazar S3 1227+25 (VER J1230+253) with the Very Energetic Radiation Imaging Telescope Array System (VERITAS). VERITAS observations of the source were triggered by the detection of a hard-spectrum GeV flare on 2015 May 15 with the Fermi-Large Area Telescope (LAT). A combined 5 hr VERITAS exposure on May 16 and 18 resulted in a strong 13σ detection with a differential photon spectral index, Γ = 3.8 ± 0.4, and a flux level at 9% of the Crab Nebula above 120 GeV. This also triggered target-of-opportunity observations with Swift, optical photometry, polarimetry, and radio measurements, also presented in this work, in addition to the VERITAS and Fermi-LAT data. A temporal analysis of the gamma-ray flux during this period finds evidence of a shortest variability timescale of τ obs = 6.2 ± 0.9 hr, indicating emission from compact regions within the jet, and the combined gamma-ray spectrum shows no strong evidence of a spectral cutoff. An investigation into correlations between the multiwavelength observations found evidence of optical and gamma-ray correlations, suggesting a single-zone model of emission. Finally, the multiwavelength spectral energy distribution is well described by a simple one-zone leptonic synchrotron self-Compton radiation model.

Keywords: Jets, High energy astrophysics, Blazars, Active galactic nuclei, Gamma-rays
Fading AGNs in Poststarburst Galaxies. The role of active galactic nuclei (AGNs) in quenching galaxies and driving the evolution from star forming to quiescence remains a key question in galaxy evolution. We present evidence from the Mapping Nearby Galaxies at APO survey for fading AGN activity in 6/93 poststarburst galaxies. These six galaxies show extended emission line regions (EELRs) consistent with ionization from past AGN activity, analogous to "Hanny's Voorwerp" and other systems where the [O III] λ5007 emission is bright enough to be visible in broadband imaging. Using the infrared luminosities from IRAS to estimate the current AGN luminosities, we find that 5/6 of the poststarburst galaxies have current AGNs which have faded from the peak luminosity required to have ionized the EELRs. Given the rate at which we observe EELRs, the typical EELR visibility timescale, and an estimate of how often EELRs would be visible, we estimate the duty cycle of AGN activity during the poststarburst phase. The timescale for the galaxy to cycle between peaks in AGN luminosity is t EELR ~ 1.1-2.3 × 105 yr. Given the rate at which we observe current AGN activity during this phase, we estimate that the AGN spends only 5.3% of this time (or t ON = 0.6-1.3 × 104 yr) in its luminous phase, with the rest of the time spent "off" or in a low-luminosity phase. The length of this duty cycle may explain why so few luminous AGNs have been observed during the poststarburst phase, despite evidence for AGN feedback at work.

Keywords: AGN host galaxies, Post-starburst galaxies, E+A galaxies
The Evolution of the 1/f Range within a Single Fast-solar-wind Stream between 17.4 and 45.7 Solar Radii. The power spectrum of magnetic field fluctuations in the fast solar wind (V SW &gt; 500 km s-1) at magnetohydrodynamic scales is characterized by two different power laws on either side of a break frequency f b. The low-frequency range at frequencies f smaller than f b is often viewed as the energy reservoir that feeds the turbulent cascade at f &gt; f b. At heliocentric distances r exceeding 60 solar radii (R s), the power spectrum often has a 1/f scaling at f &lt; f b, i.e., the spectral index is close to -1. In this study, measurements from the Parker Solar Probe's Encounter 10 with the Sun are used to investigate the evolution of the magnetic field power spectrum at f &lt; f b at r &lt; 60 R s during a fast radial scan of a single fast-solar-wind stream. We find that the spectral index in the low-frequency part of the spectrum decreases from approximately -0.61 to -0.94 as r increases from 17.4 to 45.7 R s. Our results suggest that the 1/f spectrum that is often seen at large r in the fast solar wind is not produced at the Sun, but instead develops dynamically as the wind expands outward from the corona into the interplanetary medium.

Keywords: Interplanetary turbulence, Magnetohydrodynamics, Solar wind
The "Canonical" White Dwarf Cooling Sequence of M5. Recently, slowly cooling white dwarfs (WDs) are a new class of WD that have been identified in two globular clusters (namely M13 and NGC 6752), showing a horizontal branch (HB) morphology with an extended blue tail. The cooling rate of these WDs is reduced by stable thermonuclear hydrogen burning in their residual envelope, and they are thought to originate by stars that populate the blue tail of the HB and then skip the asymptotic giant branch phase. Consistently, no evidence of such kind of WDs has been found in M3, a similar cluster with no blue extension of the HB. To further explore this phenomenon, we took advantage of deep photometric data acquired with the Hubble Space Telescope in the near-ultraviolet and investigated the bright portion of the WD cooling sequence in M5, another Galactic globular cluster with HB morphology similar to M3. The normalized WD luminosity function derived in M5 was found to be impressively similar to that observed in M3, in agreement with the fact that the stellar mass distribution along the HB of these two systems is almost identical. The comparison with theoretical predictions is consistent with the fact that the cooling sequence in this cluster is populated by canonical (fast cooling) WDs. Thus, the results presented in this paper provide further support to the scenario proposing a direct causal connection between the slow cooling WD phenomenon and the horizontal branch morphology of the host stellar cluster.

Keywords: Globular star clusters, Luminosity function, White dwarf stars, HST photometry, Ultraviolet photometry, Hertzsprung Russell diagram
Which Component of Solar Magnetic Field Drives the Evolution of Interplanetary Magnetic Field over the Solar Cycle?. The solar magnetic structure changes over the solar cycle. It has a dipole structure during solar minimum, where the open flux extends mainly from the polar regions into the interplanetary space. During maximum, a complex structure is formed with low-latitude active regions and weakened polar fields, resulting in spread open field regions. However, the components of the solar magnetic field that are responsible for long-term variations in the interplanetary magnetic field (IMF) are not clear, and the IMF strength estimated based on the solar magnetic field is known to be underestimated by a factor of 3-4 against the actual in situ observations (the open flux problem). To this end, we decomposed the coronal magnetic field into the components of the spherical harmonic function of degree and order (ℓ, m) using the potential field source surface model with synoptic maps from SDO/HMI for 2010-2021. As a result, we found that the IMF rapidly increased in 2014 December (7 months after the solar maximum), which coincided with the increase in the equatorial dipole, (ℓ, m) = (1, ±1), corresponding to the diffusion of active regions toward the poles and in the longitudinal direction. The IMF gradually decreased until 2019 December (solar minimum) and its variation corresponded to that of the nondipole component ℓ ≥ 2. Our results suggest that the understanding of the open flux problem may be improved by focusing on the equatorial dipole and the nondipole component and that the influence of the polar magnetic field is less significant.

Keywords: Solar photosphere, Heliosphere, Interplanetary magnetic fields, Solar magnetic fields, Solar corona, Solar coronal holes
Nature, Generation, and Dissipation of Alfvénic Kinks/Switchbacks Observed by Parker Solar Probe and WIND. The discovery of very prominent magnetic kinks/switchbacks in the solar wind within 0.3 au has become a scientific highlight of the Parker Solar Probe (PSP) mission. This discovery points at the promising impact of small-scale solar activity on the inner heliosphere. To address the nature, generation, and dissipation of these kinks, we perform a statistical analysis of the plasma and boundary properties of the kinks using PSP multi-encounter observations and WIND measurements at 1 au. The kinks show strong Alfvénicity and velocity fluctuations of the order of the local Alfvén speed. These findings suggest that the nature of the kinks is consistent with large-amplitude Alfvén pulses, and the steepening of these Alfvén pulses is likely the formation mechanism of these kinks. Based on the angle between the normal direction of the kinks' boundaries and the background magnetic field vector, PSP kinks and WIND kinks can be divided into two groups: quasi-parallel and quasi-perpendicular kinks. We speculate that quasi-parallel kinks form through the coupling of Alfvén and fast waves as launched from coronal interchange magnetic reconnection. In contrast, quasi-perpendicular kinks may come from the steepening of Alfvén waves launched from both coronal interchange magnetic reconnection and from the more inhomogeneous lower solar atmosphere. We find that the kink velocity perturbation gradually decreases during outward propagation and is much lower than expected from WKB theory, suggesting a progressive dissipation of the kinks. Comparing PSP kinks and WIND kinks, we conjecture that the kinks dissipate through merging with the turbulent energy cascade within 0.25 au.

Keywords: Interplanetary turbulence, Interplanetary discontinuities, Solar wind
Harnessing Unresolved Lensed Quasars: The Mathematical Foundation of the Fluctuation Curve. Strong gravitational lensed quasars (QSOs) have emerged as powerful and novel cosmic probes as they can deliver crucial cosmological information, such as a measurement of the Hubble constant, independent of other probes. Although the upcoming LSST survey is expected to discover 103-104 lensed QSOs, a large fraction will remain unresolved due to seeing. The stochastic nature of the quasar intrinsic flux makes it challenging to identify lensed quasars and measure the time delays using unresolved light-curve data only. In this regard, Bag et al. introduced a data-driven technique based on the minimization of the fluctuation in the reconstructed image light curves. In this article, we delve deeper into the mathematical foundation of this approach. We show that the lensing signal in the fluctuation curve is dominated by the autocorrelation function (ACF) of the derivative of the joint light curve. This explains why the fluctuation curve enables the detection of the lensed QSOs only using the joint light curve, without making assumptions about QSO flux variability, nor requiring any additional information. We show that the ACF of the derivative of the joint light curve is more reliable than the ACF of the joint light curve itself because intrinsic quasar flux variability shows significant autocorrelation up to a few hundred days (as they follow a red power spectrum). In addition, we show that the minimization of fluctuation approach provides even better precision and recall as compared to the ACF of the derivative of the joint light curve when the data have significant observational noise.

Keywords: Strong gravitational lensing, Astrostatistics techniques, Quasars
Characterizing the Conditional Galaxy Property Distribution Using Gaussian Mixture Models. Line-intensity mapping (LIM) is a promising technique to constrain the global distribution of galaxy properties. To combine LIM experiments probing different tracers with traditional galaxy surveys and fully exploit the scientific potential of these observations, it is necessary to have a physically motivated modeling framework. As part of developing such a framework, in this work, we introduce and model the conditional galaxy property distribution (CGPD), i.e., the distribution of galaxy properties conditioned on the host halo mass and redshift. We consider five galaxy properties, including the galaxy stellar mass, molecular gas mass, galaxy radius, gas-phase metallicity, and star formation rate (SFR), which are important for predicting the emission lines of interest. The CGPD represents the full distribution of galaxies in the five-dimensional property space; many important galaxy distribution functions and scaling relations, such as the stellar mass function and SFR main sequence, can be derived from integrating and projecting it. We utilize two different kinds of cosmological galaxy simulations, a semi-analytic model and the IllustrisTNG hydrodynamic simulation, to characterize the CGPD and explore how well it can be represented using a Gaussian mixture model (GMM). We find that with just a few (approximately three) Gaussian components, a GMM can describe the CGPD of the simulated galaxies to high accuracy for both simulations. The CGPD can be mapped to LIM or other observables by constructing the appropriate relationship between galaxy properties and the relevant observable tracers, which will be discussed in future works.

Keywords: Gaussian mixture model, Astrostatistics distributions, Galaxy evolution, Line intensities, Astrostatistics strategies
The Lively Accretion Disk in NGC 2992. III. Tentative Evidence of Rapid Ultrafast Outflow Variability. We report on the 2019 XMM-Newton+NuSTAR monitoring campaign of the Seyfert galaxy NGC 2992, observed at one of its highest flux levels in the X-rays. The time-averaged spectra of the two XMM-Newton orbits show ultrafast outflows (UFOs) absorbing structures above 9 keV with &gt;3σ significance. A detailed investigation of the temporal evolution on a ~5 ks timescale reveals UFO absorption lines at a confidence level &gt;95% (2σ) in 8 out of 50 XMM-Newton segments, estimated via Monte Carlo simulations. We observe a wind variability corresponding to a length scale of 5 Schwarzschild radii r  S . Adopting the novel Wind in the Ionized Nuclear Environment model, we estimate the outflowing gas velocity (v = 0.21-0.45c), column density (N H = 4-8 × 1024 cm-2) and ionization state ( $\mathrm{log}({\xi }_{0}/\mathrm{erg}\ \mathrm{cm}\ {{\rm{s}}}^{-1})=3.7\mbox{--}4.7$ ), taking into account geometrical and special relativity corrections. These parameters lead to instantaneous mass outflow rates of ${\dot{M}}_{\mathrm{out}}\simeq 0.3\mbox{--}0.8$ M ☉ yr-1, with associated outflow momentum rates ${\dot{p}}_{\mathrm{out}}\simeq 20\mbox{--}90$ L Bol/c and kinetic energy rates ${\dot{E}}_{{\rm{K}}}\simeq 2\mbox{--}25$ L Bol. We estimate a wind duty cycle of ≈12% and a total mechanical power of ≈2 times the active galactic nuclei (AGN) bolometric luminosity, suggesting that the wind may drive significant feedback effects between the AGN and the host galaxy. Notably, we also provide an estimate for the wind launching radius and density of ≈5r  S , 1011 cm-3, respectively.

Keywords: Active galactic nuclei, Photoionization, X-ray active galactic nuclei
Core-collapse Supernova Explosions in Active Galactic Nucleus Accretion Disks. Astrophysical events that occur in active galactic nucleus (AGN) disks are believed to differ significantly from the ordinary in the interstellar medium. We show that stars located in the outer region of the AGN disk would explode near the original migration starting points instead of being accreted by the central supermassive black hole owing to the effect of viscosity. AGN disks provide a dense environment for supernova (SN) explosions, which inevitably involve ejecta-disk interactions. In this paper, we investigate the light curves (LCs) of core-collapse SNe that exploded in AGN disks. In addition to the fundamental energy source of the 56Ni-56Co-56Fe decay reaction powering the SN LCs, the forward/reverse shock produced during interactions may contribute significantly to the observed flux. If the stellar winds manage to create a cavity surrounded by a shell near the star before the SN explosion, the ejecta-winds-disk configurations are expected. We present various SN LCs from different types of progenitors and find that the SN LCs are dominated by the radiation of ejecta-disk interaction induced shocks. The resulting SNe in the AGN disk are promising transient sources for UV and optical band detection by the Neil Gehrels Swift Observatory, the Ultraviolet Explorer, and wide-field survey telescopes such as the Ultraviolet Transient Astronomy Satellite, the Wide Field Survey Telescope, and the Legacy Survey of Space and Time at the Vera C. Rubin Observatory. These detections could aid in the investigation of AGN disks and the associated high-energy transient occurrences.

Keywords: Stellar winds, Galaxy accretion disks, Supernova dynamics
Joint Modeling of Radial Velocities and Photometry with a Gaussian Process Framework. Developments in the stability of modern spectrographs have led to extremely precise instrumental radial velocity (RV) measurements. For most stars, the detection limit of planetary companions with these instruments is expected to be dominated by astrophysical noise sources such as starspots. Correlated signals caused by rotationally modulated starspots can obscure or mimic the Doppler shifts induced by even the closest, most massive planets. This is especially true for young, magnetically active stars where stellar activity can cause fluctuation amplitudes of ≳0.1 mag in brightness and ≳100 m s-1 in RV semiamplitudes. Techniques that can mitigate these effects and increase our sensitivity to young planets are critical to improving our understanding of the evolution of planetary systems. Gaussian processes (GPs) have been successfully employed to model and constrain activity signals in individual cases. However, a principled approach of this technique, specifically for the joint modeling of photometry and RVs, has not yet been developed. In this work, we present a GP framework to simultaneously model stellar activity signals in photometry and RVs that can be used to investigate the relationship between both time series. Our method, inspired by the FF ${}^{{\prime} }$ framework of Aigrain et al., models spot-driven activity signals as the linear combinations of two independent latent GPs and their time derivatives. We also simulate time series affected by starspots by extending the starry software to incorporate time evolution of stellar features. Using these synthetic data sets, we show that our method can predict spot-driven RV variations with greater accuracy than other GP approaches.

Keywords: Astronomy data modeling, Astronomy data analysis, Stellar activity, Photometry, Radial velocity
Parameterized Asymmetric Neutral Hydrogen Disk Integrated Spectrum Characterization (PANDISC). I. Introduction to a Physically Motivated H I Model. Modeling the integrated H I spectra of galaxies has been a difficult task, due to their diverse shapes, but more dynamical information is waiting to be explored in H I line profiles. Based on simple assumptions, we construct a physically motivated model for the integrated H I spectra: Parameterized Asymmetric Neutral hydrogen Disk Integrated Spectrum Characterization (PANDISC). The model shows great flexibility in reproducing the diverse H I profiles. We use Monte Carlo Markov Chain for fitting the model to global H I profiles and produce statistically robust quantitative results. Comparing with several samples of H I data available in the literature, we find the model-fitted widths agree with cataloged velocity widths (e.g., W50) down to S/N ≲ 6. While dynamical information can only be extracted reliably from spectra with S/N &gt; 8. The model is also shown to be useful for applications like the baryonic Tully-Fisher relation (BTFR) and profile-based sample control. By comparing the model parameter v  r  to v flat, we uncover how the H I width is affected by the structure of the rotation curve, following a trend consistent with the difference in the BTFR slope. We also select a sample of spectra with broad wing-like features suggestive of a population of galaxies with unusual gas dynamics. The PANDISC model bears both promise and limitations for potential use beyond H I lines. Further application on the whole ALFALFA sample will enable us to perform large-scale ensemble studies of the H I properties and dynamics in nearby galaxies.

Keywords: Galaxy dynamics, Galaxy rotation, Astronomy data analysis, H I line emission
Deciphering Faint Gyrosynchrotron Emission from a Coronal Mass Ejection Using Spectropolarimetric Radio Imaging. Measurements of the plasma parameters of coronal mass ejections (CMEs), particularly the magnetic field and nonthermal electron population entrained in the CME plasma, are crucial to understand their propagation, evolution, and geo-effectiveness. Spectral modeling of gyrosynchrotron (GS) emission from CME plasma has been regarded as one of the most promising remote-sensing techniques for estimating spatially resolved CME plasma parameters. Imaging the very low flux density CME GS emission in close proximity to the Sun with orders of magnitude higher flux density has, however, proven to be rather challenging. This challenge has only recently been met using the high dynamic range imaging capability of the Murchison Widefield Array (MWA). Although routine detection of GS is now within reach, the challenge has shifted to constraining the large number of free parameters in GS models, a few of which are degenerate, using the limited number of spectral points at which the observations are typically available. These degeneracies can be broken using polarimetric imaging. For the first time, we demonstrate this using our recently developed capability of high-fidelity polarimetric imaging on the data from the MWA. We show that spectropolarimetric imaging, even when only sensitive upper limits on circularly polarization flux density are available, is not only able to break the degeneracies but also yields tighter constraints on the plasma parameters of key interest than possible with total intensity spectroscopic imaging alone.

Keywords: Space weather, Solar physics, Solar radio emission, Solar magnetic fields, Solar coronal mass ejections
Semi-analytical Expression of G-mode Period Spacing: The Case of Brunt-Väisälä Frequency with Not a Jump but a Ramp. To decipher complex patterns of gravity-mode period spacings observed for intermediate-mass main-sequence stars is an important step toward a better understanding of the structure and dynamics in the deep radiative region of the stars. In this study, we apply the JWKB approximation to derive a semi-analytical expression of the g-mode period spacing pattern, for which the gradient in the Brunt-Väisälä frequency is taken into account. The formulation includes the term P -1 B ⋆, where P and B ⋆ represent the g-mode period and degree of the structural variation, the latter of which especially is related to the steepness of the gradient of the Brunt-Väisälä frequency. Tests with one-dimensional stellar models show that the semi-analytical expression derived in this study is useful for inferring the degree of the structural variation B ⋆ with an accuracy of ~10 % in the case of relatively massive intermediate-mass models with the mass M larger than 3 M ⊙. The newly formulated expression will possibly allow us to put further constraints on, e.g., mixing processes inside intermediate-mass main-sequence g-mode pulsators such as β Cep, SPB, and γ Dor stars that have been principal targets in asteroseismology.

Keywords: Stellar interiors, Stellar cores, Stellar oscillations, Asteroseismology, Stellar evolution