Catálogo de publicaciones - revistas

<jats:title>Abstract</jats:title> <jats:p>Spatially resolved images of debris disks frequently reveal complex morphologies such as gaps, spirals, and warps. Most existing models for explaining such morphologies focus on the role of massive perturbers (i.e., planets, stellar companions), ignoring the gravitational effects of the disk itself. Here we investigate the secular interaction between an eccentric planet and a massive, external debris disk using a simple analytical model. Our framework accounts for both the gravitational coupling between the disk and the planet, as well as the disk self-gravity—with the limitation that it ignores the non-axisymmetric component of the disk (self-)gravity. We find generally that even when the disk is less massive than the planet, the system may feature secular resonances within the disk (contrary to what may be naively expected), where planetesimal eccentricities get significantly excited. Given this outcome, we propose that double-ringed debris disks, such as those around HD 107146 and HD 92945, could be the result of secular resonances with a yet-undetected planet interior to the disk. We characterize the dependence of the properties of the secular resonances (i.e., locations, timescales, and widths) on the planet and disk parameters, finding that the mechanism is robust provided the disk is massive enough. As an example, we apply our results to HD 107146 and find that this mechanism readily produces ∼20 au wide non-axisymmetric gaps. Our results may be used to set constraints on the total mass of double-ringed debris disks. We demonstrate this for HD 206893, for which we infer a disk mass of ≈170<jats:italic>M</jats:italic> <jats:sub>⊕</jats:sub> by considering perturbations from the known brown dwarf companion.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The Large Magellanic Cloud supernova remnant J0454-6713 abutting the H <jats:sc>ii</jats:sc> region N9 has been observed with XMM-Newton. Two groups of lines from Fe <jats:sc>xvii</jats:sc> account for half the emission and lines from Fe <jats:sc>xviii</jats:sc>, O <jats:sc>vii</jats:sc>, and O <jats:sc>viii</jats:sc> are also clearly detected with the XMM RGS. Isothermal equilibrium fits of the EPIC spectra reproduce the basic spectral form and show little variation throughout the remnant but are insensitive to the lines from the high-temperature ions. These are overwhelmed in the EPIC cameras by the dominant Fe <jats:sc>xvii</jats:sc> radiation and the EPIC best-fit spectra do not agree with the RGS data. Uncertainties in the atomic data used to determine Fe-line strength present a further complication which inhibits a good EPIC spectral fit. We build a two-temperature model which does fit both RGS and EPIC results and propose that the high-T component is from SN debris and the low from heated material in the H <jats:sc>ii</jats:sc> region. The high ratio of Fe emission to that from O requires the remnant to be the product of a Type Ia supernova and points to a deflagration–detonation origin. Weak X-ray emission from the N9 superbubble is detected and briefly discussed. The abundance of Ne in N9 material seems higher than average for the LMC in both the superbubble spectrum and the low-temperature component of the remnant RGS spectrum.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The thermodynamic properties of the hot plasma in galaxy clusters retain information on the processes leading to the formation and evolution of the gas in their deep, dark matter potential wells. These processes are dictated not only by gravity but also by gas physics, e.g., active galactic nucleus feedback and turbulence. In this work, we study the thermodynamic properties, e.g., density, temperature, pressure, and entropy, of the most massive and the most distant (seven clusters at <jats:italic>z</jats:italic> &gt; 1.2) clusters selected by the South Pole Telescope and compare them with those of the nearby clusters (13 clusters at <jats:italic>z</jats:italic> &lt; 0.1) to constrain their evolution as a function of time and radius. We find that thermodynamic properties in the outskirts of high-redshift clusters are remarkably similar to the low-redshift clusters, and their evolution follows the prediction of the self-similar model. Their intrinsic scatter is larger, indicating that the physical properties that lead to the formation and virialization of cluster outskirts show evolving variance. On the other hand, thermodynamic properties in the cluster cores deviate significantly from self-similarity, indicating that the processes that regulate the core are already in place in these very high redshift clusters. This result is supported by the unevolving physical scatter of all thermodynamic quantities in cluster cores.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The existence of strange matter in compact stars may give rise to striking outcomes of the various physical phenomena. As an alternative to neutron stars, a new class of compact stars called strange stars should exist if the strange matter hypothesis is true. In this paper, we investigate the possible construction of strange stars in quark matter phases based on the MIT bag model. We consider scenarios in which strange stars have no crusts. Then we apply two types of equations of state to quantify the mass–radius diagram for static strange star models, performing the numerical calculation of the modified Tolman–Oppenheimer–Volkoff equations in the context of 4D Einstein–Gauss–Bonnet (EGB) gravity. It is worth noting that the GB term gives rise to a nontrivial contribution to the gravitational dynamics in the limit <jats:italic>D</jats:italic> → 4. However, the claim that the resulting theory is one of pure gravity has been cast in doubt on several grounds. Thus, we begin our discussion by showing the regularized 4D EGB theory has an equivalent action as the novel 4D EGB in a spherically symmetric spacetime. We also study the effects of coupling constant <jats:italic>α</jats:italic> on the physical properties of the constructed strange stars including the compactness and criterion of adiabatic stability. Finally, we compare our results to those obtained from standard general relativity.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The pure rotational spectrum of the CCl<jats:sup>+</jats:sup> (<jats:italic>X</jats:italic> <jats:sup>1</jats:sup>Σ<jats:sup>+</jats:sup>) cation has been observed for the first time using a cryogenic ion trap apparatus and applying an action spectroscopy scheme. The major isotopic species <jats:sup>12</jats:sup>C<jats:sup>35</jats:sup>Cl<jats:sup>+</jats:sup> was observed up to the <jats:italic>J</jats:italic> = 4 ← 3 transition around 191 GHz and <jats:sup>12</jats:sup>C<jats:sup>37</jats:sup>Cl<jats:sup>+</jats:sup> was observed up to <jats:italic>J</jats:italic> = 3 ← 2. All transitions exhibit (partially) resolved hyperfine structure from the presence of the chlorine nuclei (both <jats:italic>I</jats:italic> = 3/2). This study provides the data needed for future sensitive radio astronomical searches for CCl<jats:sup>+</jats:sup> in space.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Some subtle distinctions between optically thin emission and optically thick emission (with a dynamically passive source of opacity) from an emitting surface are drawn. It is noted that photons may escape a region of high optical depth by dragging the opaque material with them, and that optically thick emission can have a shorter scale of variation than optically thin emission and less light echoing.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We present High Sensitivity Array and enhanced Multi-Element Remotely Linked Interferometer Network observations of the radio-loud broad-lined Type Ic supernova PTF11qcj obtained ∼7.5 yr after the explosion. Previous observations of this supernova at 5.5 yr since explosion showed a double-peaked radio light curve accompanied by a detection in the X-rays, but no evidence for broad H<jats:italic>α</jats:italic> spectral features. The Very Long Baseline Interferometry (VLBI) observations presented here show that the PTF11qcj GHz radio ejecta remains marginally resolved at the submilliarcsecond level ≈7.5 yr after the explosion, pointing toward a nonrelativistic expansion. Our VLBI observations thus favor a scenario in which the second peak of the PTF11qcj radio light curve is related to the strong interaction of the supernova ejecta with a circumstellar medium of variable density, rather than to the emergence of an off-axis jet. Continued VLBI monitoring of PTF11qcj in the radio may further strengthen this conclusion.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We report strong linear correlation between shifted velocity and line width of the broad blueshifted [O <jats:sc>iii</jats:sc>] components in Sloan Digital Sky Survey (SDSS) quasars. Broad blueshifted [O <jats:sc>iii</jats:sc>] components are commonly treated as indicators of outflows related to a central engine; however, it is still an open question whether the outflows are related to central accretion properties or related to local physical properties of narrow emission-line regions (NLRs). Here, the reported strong linear correlation with Spearman rank correlation coefficient 0.75 can be expected under the assumption of active galactic nuclei (AGNs) feedback-driven outflows, through a large sample of 535 SDSS quasars with reliable blueshifted broad [O <jats:sc>iii</jats:sc>] components. Moreover, there are very different detection rates for broad blueshifted and broad redshifted [O <jats:sc>iii</jats:sc>] components in quasars, and no positive correlation can be found between shifted velocity and line width of the broad redshifted [O <jats:sc>iii</jats:sc>] components, which provides further and strong evidence to reject the possibility of local outflows in NLRs leading to the broad blueshifted [O <jats:sc>iii</jats:sc>] components in quasars. Thus, the strong linear correlation can be treated as strong evidence for the broad blueshifted [O <jats:sc>iii</jats:sc>] components being better indicators of outflows related to central engine in AGNs. Furthermore, rather than central black hole masses, Eddington ratios and continuum luminosities have key roles in the properties of the broad blueshifted [O <jats:sc>iii</jats:sc>] components in quasars.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Many approaches to galaxy dynamics assume that the gravitational potential is simple and the distribution function is time invariant. Under these assumptions there are traditional tools for inferring potential parameters given observations of stellar kinematics (e.g., Jeans models). However, spectroscopic surveys measure many stellar properties beyond kinematics. Here we present a new approach for dynamical inference, Orbital Torus Imaging, which makes use of kinematic measurements and element abundances (or other invariant labels). We exploit the fact that, in steady state, stellar labels vary systematically with orbit characteristics (actions), yet must be invariant with respect to orbital phases (conjugate angles). The orbital foliation of phase space must therefore coincide with surfaces along which all moments of all stellar label distributions are constant. Both classical-statistics and Bayesian methods can be built on this; these methods will be more robust and require fewer assumptions than traditional tools because they require no knowledge of the (spatial) survey selection function and do not involve second moments of velocity distributions. We perform a classical-statistics demonstration with red giant branch stars from the APOGEE surveys: we model the vertical orbit structure in the Milky Way disk to constrain the local disk mass, scale height, and the disk–halo mass ratio (at fixed local circular velocity). We find that the disk mass can be constrained (naïvely) at the few-percent level with Orbital Torus Imaging using only eight element-abundance ratios, demonstrating the promise of combining stellar labels with dynamical invariants.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The inverse first ionization potential (FIP) effect, the depletion in the coronal abundance of elements like Fe, Mg, and Si that are ionized in the solar chromosphere relative to those that are neutral, has been identified in several solar flares. We give a more detailed discussion of the mechanism of fractionation by the ponderomotive force associated with magnetohydrodynamic waves, paying special attention to the conditions in which inverse-FIP fractionation arises in order to better understand its relation to the usual FIP effect, i.e., the enhancement of the coronal abundance of Fe, Mg, Si, etc. The FIP effect is generated by parallel propagating Alfvén waves, with either photospheric, or more likely coronal, origins. The inverse-FIP effect arises as upward-propagating fast-mode waves with an origin in the photosphere or below refract back downwards in the chromosphere where the Alfvén speed is increasing with altitude. We give a more physically motivated picture of the FIP fractionation, based on the wave refraction around inhomogeneities in the solar atmosphere, and inspired by previous discussions of analogous phenomena in the optical trapping of particles by laser beams. We apply these insights to modeling the fractionation and find good agreement with the observations of Katsuda et al. and Dennis et al.</jats:p>