Catálogo de publicaciones - revistas

<jats:title>Abstract</jats:title> <jats:p>The electron-impact excitations from the ground state to the excited levels <jats:inline-formula> <jats:tex-math> <?CDATA $1{s}^{2}2{s}^{2}2{p}_{1/2}^{5}3{d}_{3/2}\,J=1$?> </jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjabe7f2ieqn1.gif" xlink:type="simple" /> </jats:inline-formula> and <jats:inline-formula> <jats:tex-math> <?CDATA $1{s}^{2}2{s}^{2}2{p}_{3/2}^{5}3{d}_{5/2}\,J=1$?> </jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjabe7f2ieqn2.gif" xlink:type="simple" /> </jats:inline-formula> as well as the subsequent radiative decays of neonlike Fe<jats:sup>16+</jats:sup> ions have been investigated within the framework of the multiconfigurational Dirac–Fock method and the relativistic distorted-wave theory. Special attention has been paid to emission behaviors of the astrophysically relevant resonance 3<jats:italic>C</jats:italic> and intercombination 3<jats:italic>D</jats:italic> lines emitted in the radiative decays of Fe<jats:sup>16+</jats:sup> ions. To this end, we calculate the angular distribution and linear polarization of both of the lines for a series of impact electron energies. It is found that the angular and polarization behaviors of the resonance 3<jats:italic>C</jats:italic> line are nearly the same as those of the intercombination 3<jats:italic>D</jats:italic> line. Nevertheless, the angular and polarization behaviors of both of the lines are found to be very sensitive to the impact electron energy, especially at low impact energies. Based on such a sensitivity, it is expected that high-precision angular and polarization measurements of the 3<jats:italic>C</jats:italic> and 3<jats:italic>D</jats:italic> lines could be served as a tool for revealing detailed information such as electron energy of relevant laboratory and astrophysical plasmas.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The MGRO J2019+37 region is one of the brightest sources in the sky at TeV energies. It was detected in the second HAWC catalog as 2HWC J2019+367 and here we present a detailed study of this region using data from HAWC. This analysis resolves the region into two sources: HAWC J2019+368 and HAWC J2016+371. We associate HAWC J2016+371 with the evolved supernova remnant CTB 87, although its low significance in this analysis prevents a detailed study at this time. An investigation of the morphology (including possible energy-dependent morphology) and spectrum for HAWC J2019+368 is the focus of this work. We associate HAWC J2019+368 with PSR J2021+3651 and its X-ray pulsar wind nebula, the Dragonfly nebula. Modeling the spectrum measured by HAWC and Suzaku reveals a ∼7 kyr pulsar and nebula system producing the observed emission at X-ray and <jats:italic>γ</jats:italic>-ray energies.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We present the first observational constraint on the Brackett-<jats:italic>γ </jats:italic>(Br<jats:italic>γ</jats:italic>) recombination line emission associated with the supermassive black hole at the center of our Galaxy, known as Sgr A*. By combining 13 yr of data with the adaptive optics fed integral field spectrograph OSIRIS at the W. M. Keck Observatory obtained as part of the Galactic Center Orbits Initiative, we extract the near-infrared spectrum within ∼0.2″ of the black hole and we derive an upper limit on the Br<jats:italic>γ</jats:italic> flux. The aperture was set to match the size of the disk-like structure that was recently reported based on millimeter-wave Atacama Large Millimeter/submillimeter Array (ALMA) observations of the hydrogen recombination line, H30<jats:italic>α</jats:italic>. Our stringent upper limit is at least a factor of 80 (and up to a factor of 245) below what would be expected from the ALMA measurements and strongly constrains possible interpretation of emission from this highly underluminous supermassive black hole.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>X-ray studies of jellyfish galaxies play a crucial role in understanding the interactions between the interstellar medium (ISM) and the intracluster medium (ICM). In this paper, we focused on the jellyfish galaxy JO201. By combining archival Chandra observations, Multi Unit Spectroscopic Explorer H<jats:italic>α</jats:italic> cubes, and maps of the emission fraction of the diffuse ionized gas, we investigated both its high-energy spectral properties and the spatial correlation between its X-ray and optical emissions. The X-ray emission of JO201 is provided by both the Compton-thick active galactic nucleus (<jats:italic>L</jats:italic> <jats:inline-formula> <jats:tex-math> <?CDATA ${}_{{\rm{X}}}^{0.5-10\mathrm{keV}}$?> </jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjabec82ieqn1.gif" xlink:type="simple" /> </jats:inline-formula> = 2.7 · 10<jats:sup>41</jats:sup> erg s<jats:sup>−1</jats:sup>, not corrected for intrinsic absorption) and an extended component (<jats:italic>L</jats:italic> <jats:inline-formula> <jats:tex-math> <?CDATA ${}_{{\rm{X}}}^{0.5\mbox{--}10\,\mathrm{keV}}\,\approx $?> </jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjabec82ieqn2.gif" xlink:type="simple" /> </jats:inline-formula> 1.9–4.5 · 10<jats:sup>41</jats:sup> erg s<jats:sup>−1</jats:sup>) produced by a warm plasma (<jats:italic>kT</jats:italic> <jats:inline-formula> <jats:tex-math> <?CDATA $\approx 1$?> </jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjabec82ieqn3.gif" xlink:type="simple" /> </jats:inline-formula> keV), whose luminosity is higher than expected from the observed star formation (<jats:italic>L</jats:italic> <jats:inline-formula> <jats:tex-math> <?CDATA ${}_{{\rm{X}}}\,\sim $?> </jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjabec82ieqn4.gif" xlink:type="simple" /> </jats:inline-formula> 3.8 · 10<jats:sup>40</jats:sup>erg s<jats:sup>−1</jats:sup>). The spectral analysis showed that the X-ray emission is consistent with the thermal cooling of hot plasma. These properties are similar to the ones found in other jellyfish galaxies showing extended X-ray emission. A point-to-point analysis revealed that this X-ray emission closely follows the ISM distribution, whereas <jats:monospace>CLOUDY</jats:monospace> simulations proved that the ionization triggered by this warm plasma would be able to reproduce the [O <jats:sc>i</jats:sc>]/H<jats:italic>α</jats:italic> excess observed in JO201. We conclude that the galactic X-ray emitting plasma originates on the surface of the ISM as a result of the ICM–ISM interplay. This process would entail the cooling and accretion of the ICM onto the galaxy, which could additionally fuel the star formation, and the emergence of [O <jats:sc>i</jats:sc>]/H<jats:italic>α</jats:italic> excess in the optical spectrum.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We report on the X-ray properties of the new transient Swift J0840.7−3516, discovered with Swift/BAT in 2020 February, using extensive data from Swift, MAXI, NICER, and NuSTAR. The source flux increased for ∼10<jats:sup>3</jats:sup> s after the discovery, decayed rapidly over ∼5 orders of magnitude in five days, and then remained almost constant over nine months. Large-amplitude short-term variations on timescales of 1–10<jats:sup>4</jats:sup> s were observed throughout the decay. In the initial flux rise, the source showed a hard power-law-shaped spectrum with a photon index of ∼1.0 extending up to ∼30 keV, above which an exponential cutoff was present. The photon index increased in the following rapid decay and became ∼2 at the end of the decay. A spectral absorption feature at 3–4 keV was detected in the decay. It is not straightforward to explain all the observed properties by any known class of X-ray sources. We discuss the possible nature of the source, including a Galactic low-mass X-ray binary with multiple extreme properties and a tidal disruption event by a supermassive black hole or a Galactic neutron star.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Dust attenuation of an inclined galaxy can cause additional asymmetries in observations, even if the galaxy has a perfectly symmetric structure. Taking advantage of the integral field spectroscopic data observed by the Sloan Digital Sky Survey-IV Mapping Nearby Galaxies at the Apache Point Observatory survey, we investigate the asymmetries of the emission-line and continuum maps of star-forming disk galaxies. We define new parameters, <jats:italic>A</jats:italic> <jats:sub> <jats:italic>a</jats:italic> </jats:sub> and <jats:italic>A</jats:italic> <jats:sub> <jats:italic>b</jats:italic> </jats:sub>, to estimate the asymmetries of a galaxy about its major and minor axes, respectively. Comparing <jats:italic>A</jats:italic> <jats:sub> <jats:italic>a</jats:italic> </jats:sub> and <jats:italic>A</jats:italic> <jats:sub> <jats:italic>b</jats:italic> </jats:sub> in different inclination bins, we attempt to detect the asymmetries caused by dust. For the continuum images, we find that <jats:italic>A</jats:italic> <jats:sub> <jats:italic>a</jats:italic> </jats:sub> increases with the inclination, while <jats:italic>A</jats:italic> <jats:sub> <jats:italic>b</jats:italic> </jats:sub> is a constant as inclination changes. Similar trends are found for <jats:italic>g</jats:italic> − <jats:italic>r</jats:italic>, <jats:italic>g</jats:italic> − <jats:italic>i</jats:italic>, and <jats:italic>r</jats:italic> − <jats:italic>i</jats:italic> color images. The dependence of the asymmetry on inclination suggests a thin dust layer with a scale height smaller than the stellar populations. For the H<jats:italic>α</jats:italic> and H<jats:italic>β</jats:italic> images, neither <jats:italic>A</jats:italic> <jats:sub> <jats:italic>a</jats:italic> </jats:sub> nor <jats:italic>A</jats:italic> <jats:sub> <jats:italic>b</jats:italic> </jats:sub> shows a significant correlation with inclination. Also, we do not find any significant dependence of the asymmetry of <jats:italic>E</jats:italic>(<jats:italic>B</jats:italic> − <jats:italic>V</jats:italic>)<jats:sub> <jats:italic>g</jats:italic> </jats:sub> on inclination, implying that the dust in the thick disk component is not significant. Compared to the SKIRT simulation, the results suggest that the thin dust disk has an optical depth of <jats:italic>τ</jats:italic> <jats:sub> <jats:italic>V</jats:italic> </jats:sub> ∼ 0.2. This is the first time that the asymmetries caused by the dust attenuation and the inclination are probed statistically with a large sample. Our results indicate that the combination of the dust attenuation and the inclination effects is a potential indicator of the 3D disk orientation.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The internal composition of neutron stars is currently largely unknown. Due to the possibility of phase transitions in quantum chromodynamics, stars could be hybrid and have quark cores. We investigate some imprints of elastic quark phases (only when perturbed) on the dynamical stability of hybrid stars. We show that they increase the dynamical stability window of hybrid stars in the sense that the onset of instabilities happens at larger central densities than the ones for maximum masses. In particular, when the shear modulus of a crystalline quark phase is taken at face value, the relative radius differences between elastic and perfect-fluid hybrid stars with null radial frequencies (onset of instability) would be up to 1%–2%. Roughly, this would imply a maximum relative radius dispersion (on top of the perfect-fluid predictions) of 2%–4% for stars in a given mass range <jats:italic>exclusively</jats:italic> due to the elasticity of the quark phase. In the more agnostic approach where the estimates for the quark shear modulus only suggest its possible order of magnitude (due to the many approximations taken in its calculation), the relative radius dispersion uniquely due to a quark phase elasticity might be as large as 5%–10%. Finally, we discuss possible implications of the above dispersion of radii for the constraint of the elasticity of a quark phase with electromagnetic missions such as NICER, eXTP, and ATHENA.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Observations support the hypothesis that gas disk gravitational instability might explain the formation of massive or wide-orbit gas giant exoplanets. The situation with regard to Jupiter-mass exoplanets orbiting within ∼20 au is more uncertain. Theoretical models yield divergent assessments often attributed to the numerical handling of the gas thermodynamics. Boss used the <jats:italic>β</jats:italic> cooling approximation to calculate three-dimensional hydrodynamical models of the evolution of disks with initial masses of 0.091 <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub> extending from 4 to 20 au around 1 <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub> protostars. The models considered a wide range (1–100) of <jats:italic>β</jats:italic> cooling parameters and started from an initial minimum Toomre stability parameter of <jats:italic>Q</jats:italic> <jats:sub> <jats:italic>i</jats:italic> </jats:sub> = 2.7 (gravitationally stable). The disks cooled down from initial outer disk temperatures of 180 K to as low as 40 K as a result of the <jats:italic>β</jats:italic> cooling, leading to fragmentation into dense clumps, which were then replaced by virtual protoplanets (VPs) and evolved for up to ∼500 yr. The present models test the viability of replacing dense clumps with VPs by quadrupling the spatial resolution of the grid once dense clumps form, sidestepping in most cases VP insertion. After at least ∼200 yr of evolution, the new results compare favorably with those of Boss: similar numbers of VPs and dense clumps form by the same time for the two approaches. The results imply that VP insertion can greatly speed disk instability calculations without sacrificing accuracy.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The core mass of galaxy clusters is an important probe of structure formation. Here we evaluate the use of a single-halo model (SHM) as an efficient method to estimate the strong lensing cluster core mass, testing it with ray-traced images from the Outer Rim simulation. Unlike detailed lens models, the SHM represents the cluster mass distribution with a single halo and can be automatically generated from the measured lensing constraints. We find that the projected core mass estimated with this method, <jats:italic>M</jats:italic> <jats:sub>SHM</jats:sub>, has a scatter of 8.52% and a bias of 0.90% compared to the “true” mass within the same aperture. Our analysis shows no systematic correlation between the scatter or bias and the lens-source system properties. The bias and scatter can be reduced to 3.26% and 0.34%, respectively, by excluding models that fail a visual inspection test. We find that the SHM success depends on the lensing geometry, with single giant arc configurations accounting for most of the failed cases due to their limiting constraining power. When excluding such cases, we measure a scatter and bias of 3.88% and 0.84%, respectively. Finally, we find that when the source redshift is unknown, the model-predicted redshifts are overestimated, and the <jats:italic>M</jats:italic> <jats:sub>SHM</jats:sub> is underestimated by a few percent, highlighting the importance of securing spectroscopic redshifts of background sources. Our analysis provides a quantitative characterization of <jats:italic>M</jats:italic> <jats:sub>SHM</jats:sub>, enabling its efficient use as a tool to estimate the strong lensing cluster core masses in the large samples, expected from current and future surveys.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We take a pragmatic definition of reconnection to find locations where a reconnection electric field causes an <jats:bold> <jats:italic>E</jats:italic> </jats:bold> × <jats:bold> <jats:italic>B</jats:italic> </jats:bold> drift that carries two components of the magnetic field toward their elimination. With this in mind as our target, we observe that such locations can be found using a new indicator: the velocity of the Lorentz transformation that eliminates two components of the local magnetic field. Serendipitously, the indicator naturally becomes subluminal in the close proximity of a point where two components of the magnetic field vanish and it is hard zero at the vanishing location. Everywhere else the velocity of this Lorentz frame change far exceeds the speed of light. This property can be quickly applied in practice because computing the frame change is a local operation that requires only the knowledge of the local magnetic and electric field: it can be applied in a simulation or in observational data from a field instrument. We further show that the points identified can be classified in six categories that extend the usual types of magnetic nulls to the case of 3D reconnection in the presence of a guide field. The approach is used to identify secondary electron-scale reconnection sites in a turbulent outflow from a primary reconnection site in a highly resolved massively parallel fully kinetic particle-in-cell simulation. Numerous points are found, and their detailed analysis is reported.</jats:p>