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<jats:title>Abstract</jats:title> <jats:p>Three minute oscillations in the chromosphere are attributed to both slow magnetoacoustic waves propagating from the photosphere and to oscillations generated within the chromosphere itself at its natural frequency as a response to a disturbance. Here we present an investigation of the spatial and temporal behavior of the chromospheric 3 minute oscillations before, during, and after the SOL2011-02-15T01:56 X2.2 flare. Observations in ultraviolet emission centered on 1600 and 1700 Å obtained at 24 s cadence from the Atmospheric Imaging Assembly on board the Solar Dynamics Observatory are used to create power maps as functions of both space and time. We observe higher 3 minute power during the flare, spatially concentrated in small areas ∼10 pixels (<jats:inline-formula> <jats:tex-math> <?CDATA $\sim 4^{\prime\prime} $?> </jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjabb701ieqn1.gif" xlink:type="simple" /> </jats:inline-formula>) across. This implies that the chromospheric plasma is not oscillating globally as a single body. The locations of increased 3 minute power are consistent with observations of HXR flare emission from previous studies, suggesting that these small areas are manifestations of the chromosphere responding to injection of energy by nonthermal particles. This supports the theory that the chromosphere oscillates at the acoustic cutoff frequency in response to a disturbance.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We study the neutrino pair annihilation into electron–positron pairs (<jats:inline-formula> <jats:tex-math> <?CDATA $\nu +\bar{\nu }\to {e}^{-}+{e}^{+}$?> </jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjabba2cieqn1.gif" xlink:type="simple" /> </jats:inline-formula>) near the surface of a neutron star. The analysis is performed in the framework of extended theories of gravity. The latter induce a modification of the minimum photon sphere radius (<jats:italic>R</jats:italic> <jats:sub>ph</jats:sub>) and the maximum energy deposition rate near <jats:italic>R</jats:italic> <jats:sub>ph</jats:sub>, as compared to those of general relativity. These results might lead to an efficient mechanism for generating GRBs.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>With the recent advent of circular polarization capabilities at the Atacama Large Millimeter/submillimeter Array (ALMA), Zeeman effect measurements of spectral lines are now possible as a means to directly probe line-of-sight magnetic fields in protoplanetary disks (PPDs). We present a modeling study that aims to guide physical interpretation of these anticipated observations. Using a fiducial density structure based on a typical ringed disk, we simulate line emission for the hyperfine components of the CN <jats:italic>J</jats:italic> = 1−0 transition with the POLARIS radiative transfer code. Since the expected magnetic field and typical CN distribution in PPDs remain largely unconstrained, we produce models with several different configurations. Corresponding integrated Stokes <jats:italic>I</jats:italic> and <jats:italic>V</jats:italic> profiles and 0.4 km s<jats:sup>−1</jats:sup> resolution, 1″ beam convolved channel maps are presented. We demonstrate that the emission signatures from toroidally dominated magnetic fields are distinguishable from vertically dominated magnetic field based on channel map morphology. Due to line-of-sight and beam cancellation effects, disks with toroidal <jats:inline-formula> <jats:tex-math> <?CDATA ${\boldsymbol{B}}$?> </jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjabb67aieqn1.gif" xlink:type="simple" /> </jats:inline-formula>-field configurations result in significantly diminished Stokes <jats:italic>V</jats:italic> emission. Complex magnetic fields therefore render the traditionally used method for inferring line-of-sight magnetic field strengths (i.e., fitting the derivative of the Stokes <jats:italic>I</jats:italic> to the Stokes <jats:italic>V</jats:italic> profile) ambiguous, since a given intrinsic field strength can yield a variety of Stokes <jats:italic>V</jats:italic> amplitudes depending on the magnetic field geometry. In addition, gas gaps can create structure in the integrated Stokes <jats:italic>V</jats:italic> profile that might mimic magnetic substructure. This method should therefore be applied with caution in PPD environments and can only confidently be used as a measure of magnetic field strength if the disk’s magnetic field configuration is well understood.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The Dual-zone Aperture X-ray Solar Spectrometer (DAXSS) was flown on 2018 June 18 on the NASA 36.336 sounding rocket flight and obtained the highest resolution to date for solar soft X-ray (SXR) spectra over a broad energy range. This observation was during a time with quiescent (nonflaring) small active regions on the solar disk and when the 10.7 cm radio flux (F10.7) was 75 solar flux units (1 sfu = 10–22 W m<jats:sup>−2</jats:sup> Hz<jats:sup>−1</jats:sup>). The DAXSS instrument consists of a LASP-developed dual-zone aperture and a commercial X-ray spectrometer from Amptek that measures solar full-disk irradiance from 0.5 to 20 keV with a resolving power of 20 near 1 keV. This paper discusses the novel design of the spectrometer and the instrument characterization techniques. Additionally, the solar measurements obtained from the 2018 sounding rocket flight are analyzed using CHIANTI spectral models to fit the temperatures, emission measures, and relative elemental abundances of the solar corona plasma. The abundance of iron was found to be 35% higher than expected in the quiescent Sun’s corona suggesting either that our spectral models require additional sophistication or that the underlying atomic database may require updates. Future long-term systematic observations of this spectral range are needed to provide further insight into the sources of coronal heating through modeling the changes of relative elemental abundances during developments of active regions and solar flaring events.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Cygnus X-1 is one of the brightest X-ray sources observed and shows the X-ray intensity variations on timescales from milliseconds to months in both the soft and hard X-rays. The accretion onto the black hole is believed to be wind fed due to focused stellar wind from the binary companion HDE-226868. We aim to understand the physical mechanism responsible for the short timescale X-ray variability (&lt;100 s) of the source in its hard/low state. We compute the 2D relativistic hydrodynamic simulation of the low angular momentum accretion flow with a time-dependent outer boundary condition that reflects the focused, clumpy wind from the supergiant in this X-ray binary system. We follow the dynamical evolution of our model for about 100 s and present the results showing an oscillatory shock, being a potential explanation of variability observed in hard X-rays. The simulated model with shock solutions is in good agreement with the observed power density spectra of the source.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The James Webb Space Telescope (JWST) will provide moderate-resolution transit spectra with continuous wavelength coverage from the optical to the mid-infrared for the first time. In this paper, we illustrate how different aerosol species, size distributions, and spatial distributions encode information in the JWST transit spectra of warm exoplanets. We use the transit spectral modeling code METIS, along with Mie theory and several flexible treatments of aerosol size and spatial distributions to perform parameter sensitivity studies, calculate transit contribution functions, compute Jacobians, and retrieve parameters from simulated data. The broader wavelength coverage of the JWST can encompass enough non-gray aerosol behavior to recover information about the species and size distribution of particles under many feasible aerosol scenarios. Within the JWST wavelength range, the optical and mid-infrared typically provide information about 0.1–1 <jats:italic>μ</jats:italic>m sized aerosols, while the near-infrared to mid-infrared wavelengths usually provide information about gaseous absorption. Strong gaseous absorption features in the infrared can remain visible, even when clouds and hazes are flattening the optical and near-infrared portion of the spectrum that is currently observable. For some combinations of aerosol properties, temperature, and surface gravity, one can make a precise measure of metallicity despite the presence of aerosols, but more often the retrieved metallicity of a cloudy or hazy atmosphere has significantly lower precision than for a clear atmosphere with otherwise similar properties. Future efforts to securely link aerosol properties to atmospheric metallicity and temperature in a physically motivated manner will ultimately enable a robust physical understanding of the processes at play in cloudy, hazy exoplanet atmospheres.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We use observational measurements of thermal and kinetic Sunyaev–Zel’dovich effects, as well as soft X-ray emission associated with galaxy groups, to constrain the gas density and temperature in the circumgalactic medium for dark matter halos with masses above 10<jats:sup>12.5</jats:sup> <jats:italic> M</jats:italic> <jats:sub>⊙</jats:sub>. A number of generic models are used together with a Bayesian scheme to make model inferences. We find that gas with a single temperature component cannot provide a consistent model to match the observational data. A simple two-phase model assuming a hot component and an ionized warm component can accommodate all three observations. The total amount of the gas in individual halos is inferred to be comparable to the universal baryon fraction corresponding to the halo mass. The inferred temperature of the hot component is comparable to the halo virial temperature. The fraction of the hot component increases from (15–40)% for 10<jats:sup>12.5</jats:sup> <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub> halos to (40–60)% for 10<jats:sup>14.5</jats:sup> <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub> halos, where the ranges reflect uncertainties in the assumed gas density profile. Our results suggest that a significant fraction of the halo gas is in a nonthermalized component with the temperature much lower than the virial temperature.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Magnetic flux generated within the solar interior emerges to the surface, forming active regions (ARs) and sunspots. Flux emergence may trigger explosive events—such as flares and coronal mass ejections, and therefore understanding emergence is useful for space-weather forecasting. Evidence of any pre-emergence signatures will also shed light on subsurface processes responsible for emergence. In this paper, we present a first analysis of EARs from the Solar Dynamics Observatory/Helioseismic Emerging Active Regions dataset using deep convolutional neural networks (CNN) to characterize pre-emergence surface magnetic field properties. The trained CNN classifies between pre-emergence line-of-sight magnetograms and a control set of nonemergence magnetograms with a true skill statistic (TSS) score of approximately 85% about 3 hr prior to emergence and approximately 40% about 24 hr prior to emergence. Our results are better than a baseline classification TSS obtained using discriminant analysis (DA) of only the unsigned magnetic flux, although a multivariable DA produces TSS values consistent with the CNN. We develop a network-pruning algorithm to interpret the trained CNN and show that the CNN incorporates filters that respond positively as well as negatively to the unsigned magnetic flux of the magnetograms. Using synthetic magnetograms, we demonstrate that the CNN output is sensitive to the length scale of the magnetic regions, with small-scale and intense fields producing maximum CNN output and possibly a characteristic pre-emergence pattern. Given increasing popularity of deep learning, the techniques developed here to interpret the trained CNN—using network pruning and synthetic data—are relevant for future applications in solar and astrophysical data analysis.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We report on X-ray measurements constraining the spectral energy distribution (SED) of the high-redshift <jats:italic>z</jats:italic> = 5.18 blazar SDSS J013127.34−032100.1 with new XMM-Newton and NuSTAR exposures. The blazar’s X-ray spectrum is well fit by a power law with Γ = 1.9 and <jats:inline-formula> <jats:tex-math> <?CDATA ${N}_{{\rm{H}}}=1.1\times {10}^{21}\,{\mathrm{cm}}^{-2}$?> </jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjabbb91ieqn1.gif" xlink:type="simple" /> </jats:inline-formula>, or a broken power law with <jats:inline-formula> <jats:tex-math> <?CDATA ${{\rm{\Gamma }}}_{l}=0.7$?> </jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjabbb91ieqn2.gif" xlink:type="simple" /> </jats:inline-formula>, <jats:inline-formula> <jats:tex-math> <?CDATA ${{\rm{\Gamma }}}_{h}=1.8$?> </jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjabbb91ieqn3.gif" xlink:type="simple" /> </jats:inline-formula>, and a break energy <jats:inline-formula> <jats:tex-math> <?CDATA ${E}_{b}=0.7\,\mathrm{keV}$?> </jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjabbb91ieqn4.gif" xlink:type="simple" /> </jats:inline-formula> for an expected absorbing column density of <jats:inline-formula> <jats:tex-math> <?CDATA ${N}_{{\rm{H}}}=3.6\times {10}^{20}\ {\mathrm{cm}}^{-2}$?> </jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjabbb91ieqn5.gif" xlink:type="simple" /> </jats:inline-formula>, supported by spectral fitting of a nearby bright source. No additional spectral break is found at higher X-ray energies (1–30 keV). We supplement the X-ray data with lower-energy radio-to-optical measurements and Fermi-LAT gamma-ray upper limits, construct broadband SEDs of the source, and model the SEDs using a synchro-Compton scenario. This modeling constrains the bulk Doppler factor of the jets to ≥7 and ≥6 (90%) for the low- and high-<jats:italic>N</jats:italic> <jats:sub>H</jats:sub> SEDs, respectively. The corresponding beaming implies ≥130 (low <jats:italic>N</jats:italic> <jats:sub>H</jats:sub>) or <jats:inline-formula> <jats:tex-math> <?CDATA $\geqslant 100$?> </jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjabbb91ieqn6.gif" xlink:type="simple" /> </jats:inline-formula> (high <jats:italic>N</jats:italic> <jats:sub>H</jats:sub>) high-spin supermassive black holes similar to J0131 exist at similar redshifts.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We present the Voigt profile (VP) models, column densities, Doppler <jats:italic>b</jats:italic> parameters, kinematics, and distribution of components for 422 Mg <jats:sc>ii</jats:sc> absorbers found in a survey of 249 HIRES and UVES quasar spectra. The equivalent width range of the sample is 0.006 ≤ <jats:italic>W</jats:italic> <jats:sub> <jats:italic>r</jats:italic> </jats:sub>(2796) ≤ 6.23 Å and the redshift range is 0.19 ≤ <jats:italic>z</jats:italic> ≤ 2.55, with a mean of <jats:inline-formula> <jats:tex-math> <?CDATA $\langle z\rangle =1.18$?> </jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjabbb34ieqn1.gif" xlink:type="simple" /> </jats:inline-formula>. Based on historical precedent, we classified 180 absorbers as weak systems (<jats:italic>W</jats:italic> <jats:sub> <jats:italic>r</jats:italic> </jats:sub>(2796) &lt; 0.3 Å) and 242 as strong systems (<jats:italic>W</jats:italic> <jats:sub> <jats:italic>r</jats:italic> </jats:sub>(2796) ≥ 0.3 Å). Assuming a minimum number of significant components per system, the VP fitting, yielded a total of 2989 components, with an average of 2.7 and 10.3 components found for the weak and strong Mg <jats:sc>ii</jats:sc> subsamples, respectively. The VP component line density for the full sample is 8.62 ± 0.23 clouds Å<jats:sup>−1</jats:sup>. The distribution of VP component column density over the range 12.4 ≤ log <jats:italic>N</jats:italic>(Mg <jats:sc>ii</jats:sc>) ≤ 17.0 cm<jats:sup>−2</jats:sup> is well modeled with a power-law slope of −1.45 ± 0.01. The median Doppler <jats:italic>b</jats:italic> parameters are 4.5 ± 3.5 km s<jats:sup>−1</jats:sup>, 6.0 ± 4.5 km s<jats:sup>−1</jats:sup>, and 5.7 ± 4.4 km s<jats:sup>−1</jats:sup> for the weak, strong, and full samples. We modeled the probability of component velocity splitting (the two-point velocity correlation function) of our full sample using a three-component composite Gaussian function. Our resulting velocity dispersions are <jats:italic>σ</jats:italic> <jats:sub>1</jats:sub> = 25.4 km s<jats:sup>−1</jats:sup>, <jats:italic>σ</jats:italic> <jats:sub>2</jats:sub> = 68.7 km s<jats:sup>−1</jats:sup>, and <jats:italic>σ</jats:italic> <jats:sub>3</jats:sub> = 207.1 km s<jats:sup>−1</jats:sup>. These data provide an excellent database for studying the cosmic evolution of Mg <jats:sc>ii</jats:sc> absorber kinematic evolution.</jats:p>