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<jats:title>Abstract</jats:title> <jats:p>Quiescent coronal cavities can provide insight into solar magnetic fields. They are observed in the coronal emission lines in both polarized and unpolarized light. In the total linear polarization fraction (<jats:italic>L</jats:italic>/<jats:italic>I</jats:italic>), they often possess a “lagomorphic,” or “rabbit-shaped,” structure that reflects the underlying magnetic field configuration. We studied quiescent coronal cavities observed between 2012 and 2018 by the Coronal Multichannel Polarimeter (CoMP). The majority of cavities in our study had a characteristic lagomorphic structure in linear polarization. We additionally compared cavity widths as observed in intensity with sizes of their linear polarization signatures for 70 cavities and found that both features are strongly correlated. Our results indicate that chances for observing a lagomorphic structure increase greatly with cavity lifetime, suggesting that the visibility depends on the spatial orientation of the cavity. Forward-modeled observations in linear polarization of flux ropes confirmed this assumption. We conclude that observations of the solar coronal cavities in linear polarization are consistent with the theoretical model of flux rope formation and structure.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>In van der Holst et al. (2019), we modeled the solar corona and inner heliosphere of the first encounter of NASA’s Parker Solar Probe (PSP) using the Alfvén Wave Solar atmosphere Model (AWSoM) with Air Force Data Assimilative Photospheric flux Transport–Global Oscillation Network Group magnetograms, and made predictions of the state of the solar wind plasma for the first encounter. AWSoM uses low-frequency Alfvén wave turbulence to address the coronal heating and acceleration. Here, we revise our simulations, by introducing improvements in the energy partitioning of the wave dissipation to the electron and anisotropic proton heating and using a better grid design. We compare the new AWSoM results with the PSP data and find improved agreement with the magnetic field, turbulence level, and parallel proton plasma beta. To deduce the sources of the solar wind observed by PSP, we use the AWSoM model to determine the field line connectivity between PSP locations near the perihelion at 2018 November 6 UT 03:27 and the solar surface. Close to the perihelion, the field lines trace back to a negative-polarity region about the equator.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The nuclear equation of state (EOS) is an important component in the evolution of core-collapse supernovae. In this paper we make a survey of various EOSs in the literature and analyze their effect on spherical core-collapse models in which the effects of three-dimensional turbulence is modeled by a general relativistic formulation of Supernova Turbulence In Reduced-dimensionality (STIR). We show that the viability of the explosion is quite EOS dependent and that it best correlates with the early-time interior entropy density of the proto–neutron star. We check that this result is not progenitor dependent, although the lowest-mass progenitors show different explosion properties, due to the different pre-collapse nuclear composition. Larger central entropies also induce more vigorous proto–neutron star convection in our one-dimensional turbulence model, as well as a wider convective layer.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Astrophysical ices are being exposed to ionizing radiation in space environments, which trigger new reactions and desorption processes. In the lab, such processing by radiation has revealed the appearance of several new species and complements the study of the chemical evolution of icy astrophysical scenarios. Here, we develop a computational methodology that helps to clarify the chemical evolution of ices investigated experimentally under photolysis/radiolysis processes until reaching chemical equilibrium (CE). Briefly, the code (named PROCODA) solves a system of coupled differential equations and describes the evolution of the molecular abundances with the irradiation time for ices under processing by radiation. Two experimental ice samples containing pure CO<jats:sub>2</jats:sub> and irradiated by two ionizing agents (cosmic rays and ultraviolet photons) were considered prototype systems. Here, we considered 11 different chemical species within the ice (four observed: CO<jats:sub>2</jats:sub>, CO, O<jats:sub>3</jats:sub>, and CO<jats:sub>3</jats:sub>; seven nonobserved or unknown: O, O<jats:sub>2</jats:sub>, C, C2, C<jats:sub>2</jats:sub>O, C<jats:sub>2</jats:sub>O<jats:sub>2</jats:sub>, and C<jats:sub>2</jats:sub>O<jats:sub>3</jats:sub>), 100 reaction routes (e.g., direct dissociation reactions, bimolecular and termolecular reactions) and radiation-induced desorption processes. The best-fit models provide the reaction rates, several desorption parameters, as well as the characterization of the CE phase. At CE, the percentage of nonobserved species in the UV model was almost triple the one calculated in the CR model (which also includes a lot of O and C atoms). The determined values can be employed in future astrochemical models to map chemical evolution embedded species in astrophysical regions under the presence of an ionizing radiation field.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The oxygen isotope fractionation scenario, which has been developed to explain the oxygen isotope anomaly in solar system materials, predicts that CO gas is depleted in <jats:sup>18</jats:sup>O in protoplanetary disks, where segregation between solids and gas inside disks has already occurred. Based on Atacama Large Millimeter/submillimeter Array observations, we report the first detection of HC<jats:sup>18</jats:sup>O<jats:sup>+</jats:sup>(4–3) in a Class II protoplanetary disk (TW Hya). This detection allows us to explore the oxygen isotope fractionation of CO in the disk from optically thin HCO<jats:sup>+</jats:sup> isotopologues as a proxy of optically thicker CO isotopologues. Using the H<jats:sup>13</jats:sup>CO<jats:sup>+</jats:sup>(4–3) data previously obtained with the SMA, we find that the H<jats:sup>13</jats:sup>CO<jats:sup>+</jats:sup>/HC<jats:sup>18</jats:sup>O<jats:sup>+</jats:sup> ratio in the central ≲100 au regions of the disk is 10.3 ± 3.2. We construct a chemical model of the TW Hya disk with carbon and oxygen isotope fractionation chemistry, and estimate the conversion factor from H<jats:sup>13</jats:sup>CO<jats:sup>+</jats:sup>/HC<jats:sup>18</jats:sup>O<jats:sup>+</jats:sup> to <jats:sup>13</jats:sup>CO/C<jats:sup>18</jats:sup>O. With the conversion factor (=0.8), the <jats:sup>13</jats:sup>CO/C<jats:sup>18</jats:sup>O ratio is estimated to be 8.3 ± 2.6, which is consistent with the elemental abundance ratio in the local interstellar medium (8.1 ± 0.8) within the error margin. Therefore, there is no clear evidence of <jats:sup>18</jats:sup>O depletion in CO gas in the central ≲100 au regions of the disk, although we could not draw a robust conclusion due to uncertainties. In conclusion, optically thin lines of HCO<jats:sup>+</jats:sup> isotopologues are useful tracers of CO isotopic ratios, which are not very constrained directly from optically thick lines of CO isotopologues. Future higher sensitivity observations of H<jats:sup>13</jats:sup>CO<jats:sup>+</jats:sup> and HC<jats:sup>18</jats:sup>O<jats:sup>+</jats:sup> would allow us to better constrain the oxygen fractionation in the disk.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We present the results of 3D hydrodynamic simulations of a gamma-ray burst (GRB) jet emanating from a massive star with a particular focus on the formation of high-velocity quasi-spherical ejecta and the jet-induced chemical mixing. Recent early-time optical observations of supernovae associated with GRBs (e.g., GRB 171205A/SN 2017iuk) indicate a considerable amount of heavy metals in the high-velocity outer layers of the ejecta. Using our jet simulations, we show that the density and chemical structure of the outer ejecta implied by observations can be naturally reproduced by a powerful jet penetrating the progenitor star. We consider three representative jet models with a stripped massive star, a standard jet, a weak jet, and a jet choked by an extended circumstellar medium, to clarify the differences in the dynamical evolution and the chemical properties of the ejected materials. The standard jet successfully penetrates the progenitor star and creates a quasi-spherical ejecta component (cocoon). The jet-induced mixing significantly contaminates the cocoon with heavy elements that have been otherwise embedded in the inner layer of the ejecta. The weak and choked jet models fail to produce an ultrarelativistic jet but produce a quasi-spherical cocoon with different chemical properties. We discuss the impact of the different jet−star interactions on the expected early-time electromagnetic signatures of long GRBs and how to probe the jet dynamics from observations.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Combining data from the ACS Virgo Cluster Survey and the Next Generation Virgo cluster Survey, we extend previous studies of color gradients of the globular cluster (GC) systems of the two most massive galaxies in the Virgo cluster, M87 and M49, to radii of ∼15 <jats:italic>R</jats:italic> <jats:sub> <jats:italic>e</jats:italic> </jats:sub> (∼200 kpc for M87 and ∼250 kpc for M49, where <jats:italic>R</jats:italic> <jats:sub>e</jats:sub> is the effective radius). We find significant negative color gradients, i.e., becoming bluer with increasing distance, out to these large radii. The gradients are driven mainly by the outward decrease in the ratio of red to blue GC numbers. The color gradients are also detected out to ∼15 <jats:italic>R</jats:italic> <jats:sub> <jats:italic>e</jats:italic> </jats:sub> in the red and blue subpopulations of GCs taken separately. In addition, we find a negative color gradient when we consider the satellite low-mass elliptical galaxies as a system, i.e., the satellite galaxies closer to the center of the host galaxy usually have redder color indices, for both their stars and their GCs. According to the “two phase” formation scenario of massive early-type galaxies, the host galaxy accretes stars and GCs from low-mass satellite galaxies in the second phase. So an accreted GC system naturally inherits the negative color gradient present in the satellite population. This can explain why the color gradient of the GC system can still be observed at large radii after multiple minor mergers.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Magnetic reconnection in the ergosphere is investigated for a relativistic plasma around a rotating non-Kerr black hole. For a rotating non-Kerr black hole immersed in a magnetic field generated by an externally material, antiparallel magnetic field line could form in the ergosphere due to frame dragging. Therefore, magnetic reconnection could occur in the ergosphere. This magnetic reconnection may generate negative energy at infinity by redistributing the angular momentum during the process. The results show that, taking into account the effect of the deformed parameter, extraction of energy from a rotating non-Kerr black hole by magnetic reconnection could be enhanced in the presence of a positive deformed parameter.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Ice-rich planets are formed exterior to the water ice line and thus are expected to contain a substantial amount of ice. The high ice content leads to unique conditions in the interior, under which the structure of a planet is affected by ice interaction with other metals. We apply experimental data of ice–rock interaction at high pressure, and calculate detailed thermal evolution for possible interior configurations of ice-rich planets, in the mass range of super-Earth to Neptunes (5–15 <jats:italic>M</jats:italic> <jats:sub>⊕</jats:sub>). We model the effect of migration inward on the ice-rich interior by including the influences of stellar flux and envelope mass loss. We find that ice and rock are expected to remain mixed, due to miscibility at high pressure, in substantial parts of the planetary interior for billions of years. We also find that the deep interior of planetary twins that have migrated to different distances from the star are usually similar, if no mass loss occurs. Significant mass loss results in separation of the water from the rock on the surface and emergence of a volatile atmosphere of less than 1% of the planet’s mass. The mass of the atmosphere of water/steam is limited by the ice–rock interaction. We conclude that when ice is abundant in planetary interiors the planet structure may differ significantly from the standard layered structure of a water shell on top of a rocky core. Similar structure is expected in both close-in and further-out planets.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>According to the principle of Euler similarity between laboratory and astrophysical plasmas, laboratory plasmas driven by high-power lasers have been used to simulate some aspects of astrophysical phenomena. And in doing so, they aid our understanding of shock heating, interaction structures, and the consequential evolution for astrophysical outflows within a short timescale (∼ns). In this work, we experimentally investigated the mechanism of X-ray emission originating from a hot outflow (plasma) with a velocity of around 330 km s<jats:sup>−1</jats:sup>, impinging on a cold medium. A hybrid model was set up to understand the high-resolution X-ray spectra taken at the interaction region and to deduce that charge exchange takes place in such a laboratory miniature of astrophysical outflow interacting with dense molecular clouds, as in the cases of HH 248 and Cap in M82, for example. Effects from targets with multiple electrons are also explored. A brief analysis has been performed for our laboratory analog and astrophysical objects by a dimensionless ratio of the length scale between X-ray-emitting and charge-exchange regions.</jats:p>