Sazuna/UAT_keywords huggingface dataset:
A Search of TESS Full-frame Images for an Optical Counterpart of the Repeating FRB 20180916B. Recently, an association between an optical transient, AT2020hur, and a repeating fast radio burst, FRB 20180916b, has been suggested, based on a strong positional coincidence on the sky and the temporal coincidence with one of the fast radio burst's activity periods (~6 days duration every ~16 days). This suggestion is explored further and tested in this paper, utilizing full-frame images from the Transiting Exoplanet Survey Satellite (TESS) across three of its observing periods in 2019 and 2020 (Sectors 18, 24, and 25). The discovery observations of AT2020hur took place between Sectors 18 and 24, within 5 days of the commencement of Sector 24 observations. The TESS observations cover at least six activity periods for the FRB. Thus, the TESS data provide excellent temporal coverage close in time to the discovery of AT2020hur and at known times of FRB activity and radio detection. From the TESS data, no evidence is found for repeating optical transients with the suspected emission timescale of ⪆1000 s.

Keywords: Radio transient sources
r-process Viable Outflows are Suppressed in Global Alpha-viscosity Models of Collapsar Disks. Collapsar disks have been proposed to be rich factories of heavy elements, but the major question of whether their outflows are neutron rich and could therefore represent significant sites of the rapid neutron-capture (r-) process or dominated by iron-group elements remains unresolved. We present the first global models of collapsars that start from a stellar progenitor and self-consistently describe the evolution of the disk, its composition, and its outflows in response to the imploding stellar mantle, using energy-dependent M1 neutrino transport and an α-viscosity to approximate turbulent angular-momentum transport. We find that a neutron-rich, neutrino-dominated accretion flow (NDAF) is established only marginally-either for short times or relatively low viscosities-because the disk tends to disintegrate into an advective disk already at relatively high mass-accretion rates, launching powerful outflows but preventing it from developing a hot, dense, and therefore neutron-rich core. Viscous outflows disrupt the star within ~100 s with explosion energies close to that of hypernovae. If viscosity is ignored, a stable NDAF with disk mass of about 1 M ☉ is formed but is unable to release neutron-rich ejecta, while it produces a relatively mild explosion powered by a neutrino-driven wind blown off its surface. With ejecta electron fractions close to 0.5, all models presumably produce large amounts of 56Ni. Our results suggest that collapsar models based on the α-viscosity are inefficient r-process sites and that genuinely magnetohydrodynamic effects may be required to generate neutron-rich outflows. A relatively weak effective viscosity generated by magnetohydrodynamic turbulence would improve the prospects for obtaining neutron-rich ejecta.

Keywords: Gamma-ray bursts, Explosive nucleosynthesis, Black holes, Core-collapse supernovae, R-process
The Circumstellar Material around the Type IIP SN 2021yja. The majority of Type II-plateau supernovae (SNe IIP) have light curves that are not compatible with the explosions of stars in a vacuum; instead, the light curves require the progenitors to be embedded in circumstellar matter (CSM). We report on the successful fitting of the well-observed SN IIP 2021yja as a core-collapse explosion of a massive star with an initial mass of ~15 M ⊙ and a pre-explosion radius of 631 R ⊙. To explain the early-time behavior of the broadband light curves, the presence of 0.55 M ⊙ CSM within ~2 × 1014 cm is needed. Like many other SNe IIP, SN 2021yja exhibits an early-time flux excess including ultraviolet wavelengths. This, together with the short rise time (&lt;2 days) in the gri bands, indicates the presence of a compact component in the CSM, essentially adjacent to the progenitor. We discuss the origin of the preexisting CSM, which is most likely a common property of highly convective red supergiant envelopes. We argue that the difficulty in fitting the entire light curve with one spherical distribution indicates that the CSM around the SN 2021yja progenitor was asymmetric.

Keywords: Type II supernovae, Massive stars, Radiative transfer simulations, Circumstellar matter
Photobombing Earth 2.0: Diffraction-limit-related Contamination and Uncertainty in Habitable Planet Spectra. Observing habitable exoplanets that may resemble Earth is a key priority in astronomy that is dependent on not only detecting such worlds but also ascertaining that apparent signatures of habitability are not due to other sources. Space telescopes designed to observe such worlds, such as that recommended by NASA's 2020 Astrophysics Decadal Survey, have a diffraction-limited resolution that effectively spreads light from a source in a region around the source point. In this Letter, we show that the diffraction limit of a 6 m space telescope results in a point-spread function of an Earth-like planet that may contain additional unanticipated bodies for systems at distances relevant to the proposed searches. These unexpected additional objects, such as other planets and moons, can influence obtained spectra for a putative habitable planet by producing spurious features and adding additional uncertainty to the spectra. A model of Earth observed by a 6 m space telescope as though it was an exoplanet shows that the light from the Earth would be blended with the Moon, Mercury, Venus, and Mars in various combinations and at different times for numerous combinations of distance to the system and wavelength. Given the importance of extricating the true spectra of a potentially habitable planet in order to search for biosignatures, we highlight the need to account for this effect during the development of relevant telescopes and suggest some potential means of accounting for this photobombing effect.

Keywords: Space telescopes, Habitable planets, Exoplanets, Spectroscopy
On the Nature of the Photospheric Horizontal Magnetic Field Increase in Major Solar Flares. The rapid increase of the horizontal magnetic field (B  h ) around the flaring polarity inversion line is the most prominent photospheric field change during flares. It is considered to be caused by the contraction of flare loops, the details behind which is still not fully understood. Here we investigate the B  h  increase in 35 major flares using HMI high-cadence vector magnetograms. We find that the B  h  increase is always accompanied by the increase of field inclination. It usually initiates near the flare ribbons, showing a step-like change in between the ribbons. In particular, its evolution in the early flare phase shows a close spatiotemporal correlation to flare ribbons. We further find that the B  h  increase tends to have similar intensity in confined and eruptive flares but a larger spatial extent in eruptive flares in a statistical sense. Its intensity and timescale have inverse and positive correlations to the initial ribbon separations, respectively. The results altogether are well consistent with a recent proposed scenario that suggests that the reconnection-driven contraction of flare loops enhances the photospheric B  h  according to the ideal induction equation, providing statistical evidence of the reconnection-driven origin for the B  h  increase for the first time.

Keywords: Solar activity, Solar flares, Solar magnetic fields
XMM and NuSTAR Observations of an Optically Quiescent Quasar. Optically quiescent quasars (OQQs) represent a recently systematized class of infrared-luminous active galactic nuclei (AGNs) that have galaxy-like optical continua. They may represent an interesting, brief phase in the AGN life cycle, e.g., either cocooned within high-covering-factor media or indicative of recent triggering, though their nature remains unclear. Here, we present the first targeted simultaneous X-ray observations of an OQQ, our previously identified prototype, SDSS J075139.06+402811.2 at z = 0.587. The source is significantly detected over 0.5-16 keV with XMM-Newton and NuSTAR, unambiguously confirming the presence of current accretion activity. Spectral modeling yields an intrinsic luminosity L 2-10 keV ≍ 4.4 × 1043 erg s-1, well within the AGN regime, but underluminous relative to its infrared power. It is lightly obscured, with log N H [cm-2] ≍ 22.

Keywords: X-ray astronomy, Surveys, X-ray active galactic nuclei, Active galactic nuclei, Infrared galaxies
Discovery of a Bimodal Environmental Distribution of Compact Ellipticals in the Local Universe. Low-mass compact stellar systems (CSSs; M ⋆ &lt; 1010 M ⊙) are thought to be a mixed bag of objects with various formation mechanisms. Previous surveys of CSSs were biased to relatively high-density environments and cannot provide a complete view of the environmental dependence of the formation of CSSs. We conduct the first-ever unbiased flux-limited census of nearby quiescent CSSs over a total sky area of ~200 deg2 observed by the GAMA spectroscopic survey. The complete sample includes 82 quiescent CSSs, of which 85% fall within the stellar mass range of classical compact ellipticals (cEs). By quantifying the local environment with the normalized projected distance D/R vir to the nearest luminous neighboring galaxy, we find that these CSSs have a bimodal D/R vir distribution, with one group peaking near ~0.1 × R vir (satellite) and the other peaking near ~10 × R vir (field). In contrast to the CSSs, ordinary quiescent galaxies of similar masses have a unimodal D/R vir distribution. Satellite CSSs are older and more metal-rich than field CSSs on average. The bimodal D/R vir distribution of quiescent CSSs reinforces the existence of two distinct formation channels (tidal stripping and born-to-be) for cEs and may be understood in two mutually inclusive perspectives, i.e., substantial tidal stripping happens only when satellite galaxies travel sufficiently close to their massive hosts, and there exists an excess of high-density cE-bearing subhalos close to massive halos.

Keywords: Galaxy formation, Compact galaxies, Stellar populations, Compact dwarf galaxies, Tidal interaction, Elliptical galaxies
Turbulence and Waves in the Sub-Alfvénic Solar Wind Observed by the Parker Solar Probe during Encounter 10. During its 10th orbit around the Sun, the Parker Solar Probe sampled two intervals where the local Alfvén speed exceeded the solar wind speed, lasting more than 10 hours in total. In this paper, we analyze the turbulence and wave properties during these periods. The turbulence is observed to be Alfvénic and unbalanced, dominated by outward-propagating modes. The power spectrum of the outward-propagating Elsässer z + mode steepens at high frequencies while that of the inward-propagating z - mode flattens. The observed Elsässer spectra can be explained by the nearly incompressible (NI) MHD turbulence model with both 2D and Alfvénic components. The modeling results show that the z + spectra are dominated by the NI/slab component, and the 2D component mainly affects the z - spectra at low frequencies. An MHD wave decomposition based on an isothermal closure suggests that outward-propagating Alfvén and fast magnetosonic wave modes are prevalent in the two sub-Alfvénic intervals, while the slow magnetosonic modes dominate the super-Alfvénic interval in between. The slow modes occur where the wavevector is nearly perpendicular to the local mean magnetic field, corresponding to nonpropagating pressure-balanced structures. The alternating forward and backward slow modes may also be features of magnetic reconnection in the near-Sun heliospheric current sheet.

Keywords: Interplanetary turbulence, Solar wind, Solar coronal waves
Optical Continuum Reverberation in the Dwarf Seyfert Nucleus of NGC 4395. In order to constrain the size of the optical continuum emission region in the dwarf Seyfert 1 galaxy NGC 4395 through reverberation mapping, we carried out high-cadence photometric monitoring in the griz filter bands on two consecutive nights in 2022 April using the four-channel MuSCAT3 camera on the Faulkes Telescope North at Haleakalā Observatory. Correlated variability across the griz bands is clearly detected, and the r-, i-, and z-band light curves show lags of ${7.72}_{-1.09}^{+1.01}$ , ${14.16}_{-1.25}^{+1.22}$ , and ${20.78}_{-2.09}^{+1.99}$ minutes with respect to the g band when measured using the full-duration light curves. When lags are measured for each night separately, the Night 2 data exhibit lower cross-correlation amplitudes and shorter lags than the Night 1 light curves. Using the full-duration lags, we find that the lag-wavelength relationship is consistent with the τ ∝ λ 4/3 dependence found for more luminous active galactic nuclei. Combining our results with continuum lags measured for other objects, the lag between g and z band scales with optical continuum luminosity as τ gz ∝ L 0.56±0.05, similar to the scaling of broad-line region size with luminosity, reinforcing recent evidence that diffuse continuum emission from the broad-line region may contribute substantially to optical continuum variability and reverberation lags.

Keywords: Reverberation mapping, Seyfert galaxies
Gamma-Ray Eclipses and Orbital Modulation Transitions in the Candidate Redback 4FGL J1702.7-5655. Observations with the Fermi Large Area Telescope (LAT) of the gamma-ray source 4FGL J1702.7-5655, previously classified as a candidate millisecond pulsar, show highly significant modulation at a period of 0.2438033 days (~5.85 hr). Further examination of the folded light curve indicates the presence of narrow eclipses, suggesting that this is a redback binary system. An examination of the long-term properties of the modulation over 13 years of LAT observations indicates that the orbital modulation of the gamma rays changed from a simple eclipse before early 2013 to a broader, more easily detected quasi-sinusoidal modulation. In addition, the time of the eclipse shifts to ~0.05 later in phase. This change in the orbital modulation properties, however, is not accompanied by a significant overall change in gamma-ray flux or spectrum. The quasi-sinusoidal component peaks ~0.5 out of phase with the eclipse, which would indicate inferior conjunction of the compact object in the system. Swift X-ray Telescope observations reveal a possible X-ray counterpart within the LAT error ellipse. However, radio observations obtained with the Australia Telescope Compact Array do not detect a source in the region. 4FGL J1702.7-5655 appears to have changed its state in 2013, perhaps related to changes in the intrabinary shock in the system. We compare the properties of 4FGL J1702.7-5655 to those of other binary millisecond pulsars that have exhibited orbital modulation in gamma-rays.

Keywords: Neutron stars, Millisecond pulsars, Gamma-ray sources, Eclipsing binary stars, Low-mass x-ray binary stars
Light from the Darkness: Detecting Ultra-diffuse Galaxies in the Perseus Cluster through Over-densities of Globular Clusters with a Log-Gaussian Cox Process. We introduce a new method for detecting ultra-diffuse galaxies by searching for over-densities in intergalactic globular cluster populations. Our approach is based on an application of the log-Gaussian Cox process, which is a commonly used model in the spatial statistics literature but rarely used in astronomy. This method is applied to the globular cluster data obtained from the PIPER survey, a Hubble Space Telescope imaging program targeting the Perseus cluster. We successfully detect all confirmed ultra-diffuse galaxies with known globular cluster populations in the survey. We also identify a potential galaxy that has no detected diffuse stellar content. Preliminary analysis shows that it is unlikely to be merely an accidental clump of globular clusters or other objects. If confirmed, this system would be the first of its kind. Simulations are used to assess how the physical parameters of the globular cluster systems within ultra-diffuse galaxies affect their detectability using our method. We quantify the correlation of the detection probability with the total number of globular clusters in the galaxy and the anticorrelation with increasing half-number radius of the globular cluster system. The Sérsic index of the globular cluster distribution has little impact on detectability.

Keywords: Globular star clusters, Astrostatistics tools, Bayesian statistics, Astrostatistics techniques, Spatial point processes, Astrostatistics, Perseus Cluster, Low surface brightness galaxies
Classification and Jet Power of Fermi Blazars. In this work, we compile a sample of 449 Fermi blazars with the luminosity of the broadline region, the black hole mass, the beam radio luminosity, and the jet power; obtain the beam power and the black hole spin; investigate the dividing line between BL Lacertae objects (BL Lacs) and flat-spectrum radio quasars (FSRQs) to identify the discrepancies in their dominant mechanisms; and revisit the dependence of the jet power on the disk accretion luminosity, the black hole mass, and the black hole spin. We come to the following conclusions. (1) A boundary of log (L BLR/L Edd) = -3.14, separating the BL Lacs and the FSRQs, is obtained from the Bayesian analysis, which is consistent with the results from the literature. We employ the boundary to divide the blazar candidates of uncertain types into candidates for BL Lacs or FSRQs, and we find five changing-look blazars at the same time. (2) A strong correlation is found between black hole mass and intrinsic γ-ray luminosity, but a weaker correlation is found between black hole mass and observed γ-ray luminosity. The latter is weakened by jet effects: it is apparently weak for BL Lacs that have disordered amplification of the Doppler factor, since their mechanism is dominated by jets, while it is moderate for FSRQs, since their mechanism is dominated by accretion processes. (3) The jets of both FSRQs and BL Lacs are likely governed by the Blandford-Znajek mechanism.

Keywords: Accretion, Jets, Black holes, Blazars, Active galactic nuclei
A Probabilistic Autoencoder for Type Ia Supernova Spectral Time Series. We construct a physically parameterized probabilistic autoencoder (PAE) to learn the intrinsic diversity of Type Ia supernovae (SNe Ia) from a sparse set of spectral time series. The PAE is a two-stage generative model, composed of an autoencoder that is interpreted probabilistically after training using a normalizing flow. We demonstrate that the PAE learns a low-dimensional latent space that captures the nonlinear range of features that exists within the population and can accurately model the spectral evolution of SNe Ia across the full range of wavelength and observation times directly from the data. By introducing a correlation penalty term and multistage training setup alongside our physically parameterized network, we show that intrinsic and extrinsic modes of variability can be separated during training, removing the need for the additional models to perform magnitude standardization. We then use our PAE in a number of downstream tasks on SNe Ia for increasingly precise cosmological analyses, including the automatic detection of SN outliers, the generation of samples consistent with the data distribution, and solving the inverse problem in the presence of noisy and incomplete data to constrain cosmological distance measurements. We find that the optimal number of intrinsic model parameters appears to be three, in line with previous studies, and show that we can standardize our test sample of SNe Ia with an rms of 0.091 ± 0.010 mag, which corresponds to 0.074 ± 0.010 mag if peculiar velocity contributions are removed. Trained models and codes are released at https://github.com/georgestein/suPAErnova.

Keywords: Standard candles, Observational cosmology, Type Ia supernovae
Unsigned Magnetic Flux as a Proxy for Radial-velocity Variations in Sun-like Stars. A major obstacle to detecting and characterizing long-period, low-mass exoplanets is the intrinsic radial-velocity (RV) variability of host stars. To better understand RV variability, we estimate disk-averaged RV variations of the Sun over its magnetic cycle, from the Fe I line observed by SDO/HMI, using a physical model for rotationally modulated magnetic activity that was previously validated against HARPS-N solar observations. We estimate the unsigned magnetic flux and show that a linear fit to it reduces the RMS of RV variations by 62%, i.e., a factor of 2.6. We additionally apply the FF' method, which predicts RV variations based on a star's photometric variations. At cycle maximum, we find that additional processes must be at play beyond suppression of convective blueshift and velocity imbalances resulting from brightness inhomogeneities, in agreement with recent studies of RV variations. By modeling RV variations over the magnetic cycle using a linear fit to the unsigned magnetic flux, we recover injected planets at a period of ≈300 days with RV semi-amplitudes down to 0.3 m s-1. To reach 0.1 m s-1, we will need to identify and model additional phenomena that are not well traced by $| {\hat{B}}_{\mathrm{obs}}| $ or FF'. This study motivates ongoing and future efforts to develop observation and analysis techniques to measure the unsigned magnetic flux at high precision in slowly rotating, relatively inactive stars like the Sun. We conclude that the unsigned magnetic flux is an excellent proxy for rotationally modulated, activity-induced RV variations, and could become key to confirming and characterizing Earth analogs.

Keywords: Solar cycle, Quiet sun, Sunspots, Radial velocity, Active sun, Astronomy data analysis, Solar faculae, Exoplanet detection methods
Gamma-Ray Burst Constraints on Cosmological Models from the Improved Amati Correlation. An improved Amati correlation was constructed in ApJ 931 (2022) 50 by us recently. In this paper, we further study constraints on the ΛCDM and wCDM models from the gamma-ray bursts (GRBs) standardized with the standard and improved Amati correlations, respectively. By using the Pantheon Type Ia supernova sample to calibrate the latest A220 GRB data set, the GRB Hubble diagram is obtained model-independently. We find that at the high-redshift region (z &gt; 1.4) the GRB distance modulus from the improved Amati correlation is larger apparently than that from the standard Amati one. The GRB data from the standard Amati correlation only give a lower bound limit on the present matter density parameter Ωm0, while the GRBs from the improved Amati correlation constrain the Ωm0 with the 68% confidence level to be ${0.308}_{-0.230}^{+0.066}$ and ${0.307}_{-0.290}^{+0.057}$ in the ΛCDM and wCDM models, respectively, which are very consistent with those given by other current popular observational data including baryon acoustic oscillation, cosmic microwave background (CMB) radiation, and so on. Once the H(z) data are added in our analysis, the constraint on the Hubble constant H 0 can be achieved. We find that two different correlations provide slightly different H 0 results but the marginalized mean values seem to be close to that from the Planck 2018 CMB radiation observations.

Keywords: Cosmological parameters