Catálogo de publicaciones - revistas

<jats:title>Abstract</jats:title> <jats:p>We discuss the phenomenon of energization of relativistic charged particles in three-dimensional incompressible MHD turbulence and the diffusive properties of the motion of the same particles. We show that the random electric field induced by turbulent plasma motion leads test particles moving in a simulated box to be accelerated in a stochastic way, a second-order Fermi process. A small fraction of these particles happen to be trapped in large-scale structures, most likely formed due to the interaction of islands in the turbulence. Such particles get accelerated exponentially, provided their pitch angle satisfies some conditions. We discuss at length the characterization of the accelerating structure and the physical processes responsible for rapid acceleration. We also comment on the applicability of the results to realistic astrophysical turbulence.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Type Ibn supernovae (SNe Ibn) show signatures of strong interaction between the SN ejecta and hydrogen-poor circumstellar matter (CSM). Deriving the ejecta and CSM properties of SNe Ibn provides a great opportunity to study the final evolution of massive stars. In the present work, we present a light-curve (LC) model for the ejecta–CSM interaction, taking into account the processes in which the high-energy photons originally created at the forward and reverse shocks are converted to the observed emission in the optical. The model is applied to a sample of SNe Ibn and “SN Ibn” rapidly evolving transients. We show that the characteristic post-peak behavior commonly seen in the SN Ibn LCs, where a slow decay is followed by a rapid decay, is naturally explained by the transition of the forward-shock property from cooling to adiabatic regime without introducing a change in the CSM density distribution. The (commonly found) slope in the rapid-decay phase indicates a steep CSM density gradient (<jats:italic>ρ</jats:italic> <jats:sub>CSM</jats:sub> ∝ <jats:italic>r</jats:italic> <jats:sup>−3</jats:sup>), inferring a rapid increase in the mass-loss rate toward the SN as a generic property of the SN Ibn progenitors. From the derived ejecta and CSM properties, we argue that massive Wolf–Rayet stars with an initial mass of ≳18 <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub> can be a potential class of the progenitors. The present work also indicates the existence of a currently missing population of UV-bright rapid transients for which the final mass-loss rate is lower than the optical SNe Ibn, which can be efficiently probed by future UV missions.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Taking advantage of the now-available Gaia EDR3 parallaxes, we carry out an archival Hubble Space Telescope (HST) far-ultraviolet spectroscopic analysis of 10 cataclysmic variable systems, including five carefully selected eclipsing systems. We obtain accurate white dwarf (WD) masses and temperatures, in excellent agreement with the masses for four of the eclipsing systems. For three systems in our sample, BD Pav, HS 2214, and TT Crt, we report the first robust masses for their WDs. We modeled the absorption lines to derive the WD chemical abundances and rotational velocities for each of the 10 systems. As expected, for five higher-inclination (<jats:italic>i</jats:italic> ≳ 75°) systems, the model fits are improved with the inclusion of a cold absorbing slab (a curtain masking the WD) with <jats:italic>N</jats:italic> <jats:sub>H</jats:sub> ≈ 10<jats:sup>20</jats:sup>–10<jats:sup>22</jats:sup> cm<jats:sup>−2</jats:sup>. Modeling of the metal lines in the HST spectra reveals that seven of the 10 systems have significant subsolar carbon abundance, and six have subsolar silicon abundance, thereby providing further evidence that CV WDs exhibit subsolar abundances of carbon and silicon. We suggest that strong aluminum absorption lines (and iron absorption features) in the spectra of some CV WDs (such as IR Com) may be due to the presence of a <jats:italic>thin</jats:italic> iron curtain (<jats:italic>N</jats:italic> <jats:sub>H</jats:sub> ≈ 10<jats:sup>19</jats:sup> cm<jats:sup>−2</jats:sup>) rather than to suprasolar aluminum and iron abundances in the WD photosphere. The derived WD (projected) rotational velocities all fall in the range ≈100–400 km s<jats:sup>−1</jats:sup>, all sub-Keplerian similar to the values obtained in earlier studies.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We estimate the mass accretion rate (MAR) of 321 clusters of galaxies in the HectoMAP Cluster Survey. The clusters span the redshift range 0.17–0.42 and the <jats:italic>M</jats:italic> <jats:sub>200</jats:sub> mass range ≈ (0.5–3.5) × 10<jats:sup>14</jats:sup> <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub>. The MAR estimate is based on the caustic technique along with a spherical infall model. Our analysis extends the measurement of MARs for 129 clusters at <jats:italic>z</jats:italic> &lt; 0.3 from the Cluster Infall Regions in the Sloan Digital Sky Survey and the Hectospec Cluster Survey to redshift <jats:italic>z</jats:italic> ∼ 0.42. Averaging over redshift, low-mass clusters with masses near 0.7 × 10<jats:sup>14</jats:sup> <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub> roughly accrete 3 × 10<jats:sup>4</jats:sup> <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub> yr<jats:sup>−1</jats:sup>; more massive clusters with masses near 2.8 × 10<jats:sup>14</jats:sup> <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub> roughly accrete 1 × 10<jats:sup>5</jats:sup> <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub> yr<jats:sup>−1</jats:sup>. Low- and high-mass clusters increase their MAR by approximately 46% and 84%, respectively, as the redshift increases from <jats:italic>z</jats:italic> in the range 0.17–0.29 to <jats:italic>z</jats:italic> in the range 0.34–0.42. The MARs at fixed redshift increase with mass and MARs at fixed mass increase with redshift in agreement with the ΛCDM cosmological model for hierarchical structure formation. We consider the extension of MAR measurements to <jats:italic>z</jats:italic> ∼ 1.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Cosmic-ray muons detected by deep underground and underwater detectors have served as an information source on the high-energy cosmic-ray spectrum and hadronic interactions in air showers for almost a century. The theoretical interest in underground muons has nearly faded away because space-borne experiments probe the cosmic-ray spectrum more directly, and accelerators provide precise measurements of hadron yields. However, underground muons probe unique hadron interaction energies and phase space, which are still inaccessible to present accelerator experiments. The cosmic-ray nucleon energies reach the hundred-TeV and PeV ranges, which are barely accessible with space-borne experiments. Our new calculation combines two modern computational tools: <jats:sc>mceq</jats:sc> for surface muon fluxes and <jats:sc>proposal</jats:sc> for underground transport. We demonstrate excellent agreement with measurements of cosmic-ray muon intensities underground within estimated errors. Beyond that, the precision of historical data turns out to be significantly smaller than our error estimates. This result shows that the sources of high-energy atmospheric lepton flux uncertainties at the surface or underground can be significantly constrained without taking more data or building new detectors. The reduction of uncertainties can be expected to impact data analyses at large-volume neutrino telescopes and be used for the design of future ton-scale direct dark matter detectors.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We describe the energy budget of a coronal mass ejection (CME) observed on 1999 May 17 with the Ultraviolet Coronagraph Spectrometer (UVCS). We constrain the physical properties of the CME’s core material as a function of height along the corona by using the spectra taken by the single-slit coronagraph spectrometer at heliocentric distances of 2.6 and 3.1 solar radii. We use plasma diagnostics from intensity ratios, such as the O <jats:sc>vi</jats:sc> doublet lines, to determine the velocity, density, temperature, and nonequilibrium ionization states. We find that the CME core’s velocity is approximately 250 km s<jats:sup>−1</jats:sup>, and its cumulative heating energy is comparable to its kinetic energy for all of the plasma heating parameterizations that we investigated. Therefore, the CME’s unknown heating mechanisms have the energy to significantly affect the CME’s eruption and evolution. To understand which parameters might influence the unknown heating mechanism, we constrain our model heating rates with the observed data and compare them to the rate of heating generated within a similar CME that was constructed by the MAS code’s 3D MHD simulation. The rate of heating from the simulated CME agrees with our observationally constrained heating rates when we assume a quadratic power law to describe a self-similar CME expansion. Furthermore, the heating rates agree when we apply a heating parameterization that accounts for the CME flux rope’s magnetic energy being converted directly into thermal energy. This UVCS analysis serves as a case study for the importance of multislit coronagraph spectrometers for CME studies.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We quantify evolution in the cluster-scale stellar mass–halo mass (SMHM) relation’s parameters using 2323 clusters and brightest central galaxies (BCGs) over the redshift range 0.03 ≤ <jats:italic>z</jats:italic> ≤ 0.60. The precision on the inferred SMHM parameters is improved by including the magnitude gap (<jats:italic>m</jats:italic> <jats:sub>gap</jats:sub>) between the BCG and fourth-brightest cluster member (M14) as a third parameter in the SMHM relation. At fixed halo mass, accounting for <jats:italic>m</jats:italic> <jats:sub>gap</jats:sub>, through a stretch parameter, reduces the SMHM relation’s intrinsic scatter. To explore this redshift range, we use clusters, BCGs, and cluster members identified using the Sloan Digital Sky Survey C4 and redMaPPer cluster catalogs and the Dark Energy Survey redMaPPer catalog. Through this joint analysis, we detect no systematic differences in BCG stellar mass, <jats:italic>m</jats:italic> <jats:sub>gap</jats:sub>, and cluster mass (inferred from richness) between the data sets. We utilize the Pareto function to quantify each parameter’s evolution. We confirm prior findings of negative evolution in the SMHM relation’s slope (3.5<jats:italic>σ</jats:italic>), and detect negative evolution in the stretch parameter (4.0<jats:italic>σ</jats:italic>) and positive evolution in the offset parameter (5.8<jats:italic>σ</jats:italic>). This observed evolution, combined with the absence of BCG growth, when stellar mass is measured within 50 kpc, suggests that this evolution results from changes in the cluster’s <jats:italic>m</jats:italic> <jats:sub>gap</jats:sub>. For this to occur, late-term growth must be in the intracluster light surrounding the BCG. We also compare the observed results to IllustrisTNG 300-1 cosmological hydrodynamic simulations and find modest qualitative agreement. However, the simulations lack the evolutionary features detected in the real data.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Although general relativity (GR) has been precisely tested at the solar system scale, precise tests at a galactic or cosmological scale are still relatively insufficient. Here, in order to test GR at the galactic scale, we use the newly compiled galaxy-scale strong gravitational lensing (SGL) sample to constrain the parameter <jats:italic>γ</jats:italic> <jats:sub>PPN</jats:sub> in the parameterized post-Newtonian (PPN) formalism. We employ the Pantheon sample of Type Ia supernova observations to calibrate the distances in the SGL systems using the Gaussian Process method, which avoids the logical problem caused by assuming a cosmological model within GR to determine the distances in the SGL sample. Furthermore, we consider three typical lens models in this work to investigate the influences of the lens-mass distributions on the fitting results. We find that the choice of lens models has a significant impact on the constraints on the PPN parameter <jats:italic>γ</jats:italic> <jats:sub>PPN</jats:sub>. By using a minimum <jats:italic>χ</jats:italic> <jats:sup>2</jats:sup> comparison and the Bayesian information criterion as evaluation tools to make comparisons for the fitting results of the three lens models, we find that the most reliable lens model gives the result of <jats:inline-formula> <jats:tex-math> <?CDATA ${\gamma }_{\mathrm{PPN}}={1.065}_{-0.074}^{+0.064}$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mi>γ</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>PPN</mml:mi> </mml:mrow> </mml:msub> <mml:mo>=</mml:mo> <mml:msubsup> <mml:mrow> <mml:mn>1.065</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>0.074</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>0.064</mml:mn> </mml:mrow> </mml:msubsup> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjac4c3bieqn1.gif" xlink:type="simple" /> </jats:inline-formula>, which is in good agreement with the prediction of <jats:italic>γ</jats:italic> <jats:sub>PPN</jats:sub> = 1 by GR. As far as we know, our 6.4% constraint result is the best result so far among recent works using the SGL method.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The evolutionary rate of the pulsating post–asymptotic giant branch (post-AGB) star HD 161796 was suspected to be high. Spectra of HD 161796 acquired during a time span of 18 yr are analyzed with the main goal of determining the evolutionary increase in temperature and comparing it with the latest post-AGB star evolutionary models. Inspection of the spectra reveals splitting and significant temporal variation in strong absorption lines, suggesting the presence of shock waves in the atmosphere of the pulsating star. The H<jats:italic>α</jats:italic> profiles point to variable incipient mass loss. Most medium-strength lines have variable blue wings, while the red wings remain stationary, presumably due to variations in the warm outflow from the stellar surface. The modeling of the spectra suggests the average value for the effective temperature to be 7275 K, and for surface gravity, a value of log <jats:italic>g</jats:italic> = 0.7. Different iron abundances are found for different spectra, probably due to the inability to model the pulsating photosphere with stationary atmospheric models. On average, we arrive at [Fe/H] = −0.06. The observed underabundance in neutron capture and some other elements is inferred to be a consequence of dust–gas separation. It is confirmed that, during pulsation, the stellar surface is hotter when the star is smaller in size. The spectra show a 420 K range in effective temperature—a smaller variation than can be found from pulsation-related changes in color. No significant rate of evolution is seen, contrary to earlier suggestions. The initial mass of the star is evaluated to be ⪅2 <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub>.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We explore how the galaxy stellar spins acquire a peculiar tendency of being aligned with the major principal axes of the local tidal fields, in contrast to their dark matter (DM) counterparts, which tend to be perpendicular to them, regardless of their masses. Analyzing the halo and subhalo catalogs from IllustrisTNG 300 hydrodynamic simulations at <jats:italic>z</jats:italic> ≤ 1, we determine the cosines of the alignment angles, <jats:inline-formula> <jats:tex-math> <?CDATA $\cos \alpha $?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi>cos</mml:mi> <mml:mi>α</mml:mi> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjac4bdaieqn1.gif" xlink:type="simple" /> </jats:inline-formula>, between the galaxy stellar and DM spins. Creating four <jats:inline-formula> <jats:tex-math> <?CDATA $\cos \alpha $?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi>cos</mml:mi> <mml:mi>α</mml:mi> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjac4bdaieqn2.gif" xlink:type="simple" /> </jats:inline-formula>-selected samples of the galaxies and then controlling them to share the same density and mass distributions, we determine the average strengths of the alignments between the galaxy stellar spins and the tidal tensor major axes over each sample. It is clearly shown that at <jats:italic>z</jats:italic> ≤ 0.5 the more severely the galaxy stellar spin directions deviate from the DM counterparts, the stronger the peculiar tidal alignments become. Taking the ensemble averages of such galaxy properties as central black hole-to-stellar mass ratio, specific star formation rate, formation epoch, stellar-to-total mass ratio, velocity dispersions, average metallicity, and degree of the cosmic web anisotropy over each sample, we also find that all of these properties exhibit either strong correlations or anticorrelations with <jats:inline-formula> <jats:tex-math> <?CDATA $\cos \alpha $?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi>cos</mml:mi> <mml:mi>α</mml:mi> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjac4bdaieqn3.gif" xlink:type="simple" /> </jats:inline-formula>. Our results imply that the peculiar tidal alignments of the galaxy stellar spins may be caused by anisotropic occurrence of some baryonic process responsible for discharging stellar materials from the galaxies along the tidal major directions at <jats:italic>z</jats:italic> &lt; 1.</jats:p>