Catálogo de publicaciones - revistas

<jats:title>Abstract</jats:title> <jats:p>Substructures in protoplanetary disks (PPDs), whose ubiquity was unveiled by recent Atacama Large Millimeter/submillimeter Array observations, are widely discussed regarding their possible origins. We carry out global 2D magnetohydrodynamic (MHD) simulations in axisymmetry, coupled with self-consistent ray-tracing radiative transfer, thermochemistry, and nonideal MHD diffusivities. The abundance profiles of grains are also calculated based on the global dust evolution calculation, including sintering effects. We found that dust size plays a crucial role in the ring formation around the snow lines of PPDs through the accretion process. Disk ionization structures and thus tensorial conductivities depend on the size of grains. When grains are significantly larger than polycyclic aromatic hydrocarbons (PAHs), the nonideal MHD conductivities change dramatically across each snow line of major volatiles, leading to a sudden change in the accretion process across the snow lines and the subsequent formation of gaseous rings/gaps there. Specific layout of magnetic fields can suppress wind launching in certain regions by canceling out different stress components. On the other hand, the variations of conductivities are a lot less with only PAH-sized grains in disks and then these disks retain smoother radial density profiles across snow lines.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Low-frequency radio selection finds radio-bright galaxies regardless of the amount of obscuration by gas and dust. We report Chandra observations of a complete 178 MHz–selected, and so orientation-unbiased, sample of 44 0.5 &lt; <jats:italic>z</jats:italic> &lt; 1 3CRR sources. The sample is comprised of quasars and narrow-line radio galaxies (NLRGs) with similar radio luminosities, and the radio structure serves as both an age and an orientation indicator. Consistent with unification, intrinsic obscuration (measured by <jats:italic>N</jats:italic> <jats:sub>H</jats:sub>, X-ray hardness ratio, and X-ray luminosity) generally increases with inclination. However, the sample includes a population not seen in high-<jats:italic>z</jats:italic> 3CRR sources: NLRGs viewed at intermediate inclination angles with <jats:italic>N</jats:italic> <jats:sub>H</jats:sub> &lt; 10<jats:sup>22</jats:sup> cm<jats:sup>−2</jats:sup>. Multiwavelength analysis suggests that these objects have lower <jats:italic>L</jats:italic>/<jats:italic>L</jats:italic> <jats:sub>Edd</jats:sub> than typical NLRGs at similar orientation. Thus, both orientation and <jats:italic>L</jats:italic>/<jats:italic>L</jats:italic> <jats:sub>Edd</jats:sub> are important, and a “radiation-regulated unification” provides a better explanation of the sample’s observed properties. In comparison with the 3CRR sample at 1 &lt; <jats:italic>z</jats:italic> &lt; 2, our lower-redshift sample shows a higher fraction of Compton-thin NLRGs (45% versus 29%) but a similar Compton-thick fraction (20%), implying a larger covering factor of Compton-thin material at intermediate viewing angles and thus a more “puffed-up” torus atmosphere. We posit that this is due to a range of <jats:italic>L</jats:italic>/<jats:italic>L</jats:italic> <jats:sub>Edd</jats:sub> extending to lower values in this sample. In contrast, at high redshifts, the narrower range and high <jats:italic>L</jats:italic>/<jats:italic>L</jats:italic> <jats:sub>Edd</jats:sub> values allowed orientation (and so simple unification) to dominate the sample’s observed properties.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The use of the magnetic-field-induced transition (MIT) <jats:inline-formula> <jats:tex-math> <?CDATA $3{{\rm{p}}}^{4}3{\rm{d}}{}^{4}{D}_{7/2}\to 3{{\rm{p}}}^{5}\,{}^{2}{P}_{3/2}^{{\rm{o}}}$?> </jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjabfa97ieqn1.gif" xlink:type="simple" /> </jats:inline-formula> in Fe X for the measurement of the magnetic field strength in the solar corona has been discussed and demonstrated in a number of recent studies. This diagnostic technique depends on, among other conditions, the accuracy of the atomic data for Fe X. In the present work, we carry out a large-scale calculation for the atomic properties needed for the determination of the MIT rate using the multiconfiguration Dirac–Hartree–Fock method. Four computational schemes are employed to study the convergence of the atomic properties of interest. Comparison with other experimental and theoretical sources are performed and recommended values are suggested for important properties, e.g., the magnetic induced transition probabilities as a function of magnetic field strengths. The present calculations affect magnetic field measurements by decreasing the magnetic field strengths by 10%–15%, leading to differences in magnetic energy up to 30%. We recommend that the current data should be employed in magnetic field measurements in the future.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The helium-tagging technique was employed to record absorption spectra of cold anthracene cations and protonated anthracene. The evaluation of the spectra of the chromophore with a different number of attached He atoms allows getting the precise band positions of the molecular ions in the gas phase. The positions of the two most intense bands of anthracene, suitable for astrophysical detection, were found to be <jats:italic>λ</jats:italic> <jats:sub>max</jats:sub> = 3478.9 ± 1.8 Å and <jats:italic>λ</jats:italic> <jats:sub>max</jats:sub> = 7068.9 ± 5.7 Å. A considerable shift of the red band position compared to a previous measurement was attributed to a temperature effect. No coincidence of the absorption bands in astrophysical observational spectra was found. This allows estimating the upper limit for the abundance of anthracene cations per H nuclei &lt;10<jats:sup>−9</jats:sup> along the HD 183143 line of sight. We discuss possible reasons for such a low abundance of this molecular ion.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We present a new identity card for the cluster NGC 6440 in the Galactic Bulge. We have used a combination of high-resolution Hubble Space Telescope images, wide-field ground-based observations performed with the ESO-FORS2, and the public survey catalog Pan-STARRS to determine the gravitational center, projected density profile, and structural parameters of this globular from resolved star counts. The new determination of the cluster center differs by ∼2″ (corresponding to 0.08 pc) from the previous estimate, which was based on the surface brightness peak. The star density profile, extending out to 700″ from the center and suitably decontaminated from the Galactic field contribution, is best fit by a King model with a significantly higher concentration (<jats:italic>c</jats:italic> = 1.86 ± 0.06) and smaller core radius (<jats:italic>r</jats:italic> <jats:sub> <jats:italic>c</jats:italic> </jats:sub> = 6.″4 ± 0.″3) with respect to the literature values. By taking advantage of high-quality optical and near-IR color–magnitude diagrams, we also estimated the cluster age, distance, and reddening. The luminosity of the red giant branch bump was also determined. This study indicates that the extinction coefficient in the bulge in the direction of the cluster has a value (<jats:italic>R</jats:italic> <jats:sub> <jats:italic>V</jats:italic> </jats:sub> = 2.7) that is significantly lower than that traditionally used for the Galaxy (<jats:italic>R</jats:italic> <jats:sub> <jats:italic>V</jats:italic> </jats:sub> = 3.1). The corresponding best-fit values of the age, distance, and color excess of NGC 6440 are 13 Gyr, 8.3 kpc, and <jats:italic>E</jats:italic>(<jats:italic>B</jats:italic> − <jats:italic>V</jats:italic>) ∼ 1.27. These new determinations also allowed us to update the values of the central (<jats:italic>t</jats:italic> <jats:sub> <jats:italic>rc</jats:italic> </jats:sub> = 2.5 10<jats:sup>7</jats:sup> yr) and half-mass (<jats:italic>t</jats:italic> <jats:sub> <jats:italic>rh</jats:italic> </jats:sub> = 10<jats:sup>9</jats:sup> yr) relaxation times, suggesting that NGC 6440 is in a dynamically evolved stage.</jats:p>