Catálogo de publicaciones - revistas

<jats:title>Abstract</jats:title> <jats:p>The self-correlation level contours at 10<jats:sup>10</jats:sup> cm scale reveal a 2D isotropic feature in both the slow solar wind fluctuations and the fast solar wind fluctuations. However, this 2D isotropic feature is obtained based on the assumption of axisymmetry with respect to the mean magnetic field. Whether the self-correlation level contours are still 3D isotropic remains unknown. Here we perform for the first time a 3D self-correlation level contours analysis on the solar wind turbulence. We construct a 3D coordinate system based on the mean magnetic field direction and the maximum fluctuation direction identified by the minimum-variance analysis method. We use data with 1 hr intervals observed by <jats:italic>WIND</jats:italic> spacecraft from 2005 to 2018. We find, on one hand, in the slow solar wind, the self-correlation level contour surfaces for both the magnetic field and the velocity field are almost spherical, which indicates a 3D isotropic feature. On the other hand, there is a weak elongation in one of the perpendicular directions in the fast solar wind fluctuations. The 3D feature of the self-correlation level contours surfaces cannot be explained by the existing theory.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We present a new and independent determination of the local value of the Hubble constant based on a calibration of the tip of the red giant branch (TRGB) applied to Type Ia supernovae (SNe Ia). We find a value of <jats:italic>H</jats:italic> <jats:sub>0</jats:sub> = 69.8 ± 0.8 (±1.1% stat) ± 1.7 (±2.4% sys) km s<jats:sup>−1</jats:sup> Mpc<jats:sup>−1</jats:sup>. The TRGB method is both precise and accurate and is parallel to but independent of the Cepheid distance scale. Our value sits midway in the range defined by the current Hubble tension. It agrees at the 1.2<jats:italic>σ</jats:italic> level with that of the Planck Collaboration et al. estimate and at the 1.7<jats:italic>σ</jats:italic> level with the <jats:italic>Hubble Space Telescope</jats:italic> (<jats:italic>HST</jats:italic>) <jats:italic>SHoES</jats:italic> measurement of <jats:italic>H</jats:italic> <jats:sub>0</jats:sub> based on the Cepheid distance scale. The TRGB distances have been measured using deep <jats:italic>HST</jats:italic> Advanced Camera for Surveys imaging of galaxy halos. The zero-point of the TRGB calibration is set with a distance modulus to the Large Magellanic Cloud of 18.477 ± 0.004 (stat) ± 0.020 (sys) mag, based on measurement of 20 late-type detached eclipsing binary stars, combined with an <jats:italic>HST</jats:italic> parallax calibration of a 3.6 <jats:italic>μ</jats:italic>m Cepheid Leavitt law based on <jats:italic>Spitzer</jats:italic> observations. We anchor the TRGB distances to galaxies that extend our measurement into the Hubble flow using the recently completed Carnegie Supernova Project I ( CSP-I ) sample containing about 100 well-observed SNe Ia . There are several advantages of halo TRGB distance measurements relative to Cepheid variables; these include low halo reddening, minimal effects of crowding or blending of the photometry, only a shallow (calibrated) sensitivity to metallicity in the <jats:italic>I</jats:italic> band, and no need for multiple epochs of observations or concerns of different slopes with period. In addition, the host masses of our TRGB host-galaxy sample are higher, on average, than those of the Cepheid sample, better matching the range of host-galaxy masses in the CSP-I distant sample and reducing potential systematic effects in the SNe Ia measurements.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Molecules and dust produced by the atmospheres of cool evolved stars contribute to a significant amount of the total material found in the interstellar medium. To understand the mechanism behind the mass loss of these stars, it is of pivotal importance to investigate the structure and dynamics of their atmospheres. Our goal is to verify if the extended molecular and dust layers of the carbon-rich asymptotic giant branch (AGB) star V Oph, and their time variations, can be explained by dust-driven winds triggered by stellar pulsation alone, or if other mechanisms are in play. We model V Oph mid-infrared interferometric VLTI-MIDI data (8–13 <jats:italic>μ</jats:italic>m), at phases 0.18, 0.49, and 0.65, together with literature photometric data, using the latest-generation self-consistent dynamic atmosphere models for carbon-rich stars: DARWIN. We determine the fundamental stellar parameters: <jats:italic>T</jats:italic> <jats:sub>eff</jats:sub> = 2600 K, <jats:italic>L</jats:italic> <jats:sub>bol</jats:sub> = 3585 <jats:italic>L</jats:italic> <jats:sub>⊙</jats:sub>, <jats:italic>M</jats:italic> = 1.5 <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub>, C/O = 1.35, <jats:inline-formula> <jats:tex-math> <?CDATA $\dot{M}=2.50\times {10}^{-6}$?> </jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjab3419ieqn1.gif" xlink:type="simple" /> </jats:inline-formula> <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub> yr<jats:sup>−1</jats:sup>. We calculate the stellar photospheric radii at the three phases: 479, 494, 448 <jats:italic>R</jats:italic> <jats:sub>⊙</jats:sub>; and the dust radii: 780, 853, 787 <jats:italic>R</jats:italic> <jats:sub>⊙</jats:sub>. The dynamic models can fairly explain the observed <jats:italic>N</jats:italic>-band visibility and spectra, although there is some discrepancy between the data and the models, which is discussed in the text. We discuss the possible causes of the temporal variations of the outer atmosphere, deriving an estimate of the magnetic field strength, and computing upper limits for the Alfvén waves velocity. In addition, using period–luminosity sequences, and interferometric modeling, we suggest V Oph as a candidate to be reclassified as a semi-regular star.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Using the cross-matched data of <jats:italic>Gaia</jats:italic> DR2 and the 2MASS Point Source Catalog, we investigated the surface density distribution of stars aged ∼1 Gyr in the thin disk in the range of 90° ≤ <jats:italic>l</jats:italic> ≤ 270°. We selected 4654 stars above the turnoff corresponding to the age ∼1 Gyr, that fall within a small box region in the color–magnitude diagram, (<jats:italic>J</jats:italic> − <jats:italic>K</jats:italic> <jats:sub> <jats:italic>s</jats:italic> </jats:sub>)<jats:sub>0</jats:sub> versus <jats:italic>M</jats:italic>(<jats:italic>K</jats:italic> <jats:sub> <jats:italic>s</jats:italic> </jats:sub>), for which the distance and reddening are corrected. The selected sample shows an arm-like overdensity at 90° ≤ <jats:italic>l</jats:italic> ≤ 190°. This overdensity is located close to the Local Arm traced by high-mass star-forming regions (HMSFRs), but its pitch angle is slightly larger than that of the HMSFR-defined arm. Although the significance of the overdensity we report is marginal, its structure poses questions concerning both of the competing scenarios of spiral arms, the density-wave theory, and the dynamic spiral arm model. The offset between the arms traced by stars and HMSFRs, i.e., gas, is difficult to explain using the dynamic arm scenario. On the other hand, the pitch angle of the stellar Local Arm, if confirmed, is larger than that of the Perseus arm, and is difficult to explain using the classical density-wave scenario. The dynamic arm scenario can explain the pitch angle of the stellar Local Arm, if the Local Arm is in a growing up phase, while the Perseus arm is in a disrupting phase. Our result provide a new and complex picture of the Galactic spiral arms, and encourages further studies.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The interactions among objects in a mean motion resonance are important for the orbital evolution of satellites and rings, especially Saturn’s ring arcs and associated moons. In this work, we examine interactions among massive bodies in the same corotation eccentricity resonance site that affect the orbital evolution of those bodies using numerical simulations. During these simulations, the bodies exchange angular momentum and energy during close encounters, altering their orbits. This energy exchange, however, does not mean that one body necessarily moves closer to exact corotation when the other moves away from it. Indeed, if one object moves toward one of these sites, the other object is equally likely to move toward or away from it. This happens because the timescale of these close encounters is short compared to the synodic period between these particles and the secondary mass (i.e., the timescale where corotation sites can be treated as potential maxima). Because the timescale of a gravitational encounter is comparable to the timescale of a collision, we could expect energy to be exchanged in a similar way for collisional interactions. In that case, these findings could be relevant for denser systems like the arcs in Neptune’s Adams ring and how they can be maintained in the face of frequent inelastic collisions.</jats:p>