Catálogo de publicaciones - revistas

<jats:title>Abstract</jats:title> <jats:p>A radio source at the Galactic center Sgr A* is a prime supermassive black hole candidate and therefore key to developing our understanding of them. Time variations in the 230 GHz band flux of Sgr A* have been found with the Atacama Large Millimeter/submillimeter Array Cycle 5 observations. Measuring the flux density of Sgr A* in 1 minute snapshots at 217.5, 219.5, and 234.0 GHz, we obtained light curves for ten 70 minute periods. The light curves show variations at a few tens of minutes and hourly scales. The shorter timescale is similar to the orbital period of the innermost stable circular orbit around a 4 × 10<jats:sup>6</jats:sup> <jats:italic>M</jats:italic> <jats:sub>☉</jats:sub> black hole, suggesting that the variation originates from the immediate vicinity of Sgr A*. We also detected no time lag between 217.5 and 234.0 GHz and a dependence of the spectral index on the flux density.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Centaurs are minor planets thought to have originated in the outer solar system region known as the Kuiper Belt. Active Centaurs enigmatically display comet-like features (e.g., tails, comae) even though they orbit in the gas giant region where it is too cold for water to readily sublimate. Only 18 active Centaurs have been identified since 1927 and, consequently, the underlying activity mechanism(s) have remained largely unknown up to this point. Here we report the discovery of activity emanating from Centaur 2014 OG<jats:sub>392</jats:sub>, based on archival images we uncovered plus our own new observational evidence acquired with the Dark Energy Camera (Cerro Tololo Inter-American Observatory Blanco 4 m telescope), the Inamori-Magellan Areal Camera &amp; Spectrograph (Las Campanas Observatory 6.5 m Walter Baade Telescope), and the Large Monolithic Imager (Lowell Observatory 4.3 m Discovery Channel Telescope). We detect a coma as far as 400,000 km from 2014 OG<jats:sub>392</jats:sub>, and our novel analysis of sublimation processes and dynamical lifetime suggest carbon dioxide and/or ammonia are the most likely candidates for causing activity on this and other active Centaurs. We find 2014 OG<jats:sub>392</jats:sub> is optically red, but CO<jats:sub>2</jats:sub> and NH<jats:sub>3</jats:sub> are spectrally neutral in this wavelength regime so the reddening agent is as yet unidentified.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We study the angular momentum transport inside hot Jupiters under the influence of gravitational and thermal forcing. Due to the strong stellar irradiation, a radiative region develops on top of the convective region. Internal gravity waves are launched at the radiative–convective boundaries (RCBs). The thermal response is dynamical and plays an important role in the angular momentum transport. By separating the gravitational and thermal forcing terms, we identify the thermal effects of increasing the angular momentum transport. For the low-frequency (in the corotating frame with planets) prograde (retrograde) tidal frequency, the angular momentum flux is positive (negative). The tidal interactions tend to drive the planet to the synchronous state. We find that the angular momentum transport associated with the internal gravity wave is very sensitive to relative position between the RCB and the penetration depth of the thermal forcing. If the RCB is in the vicinity of the thermal forcing penetration depth, even with small amplitude thermal forcing, the thermally driven angular momentum flux could be much larger than the flux induced by gravitational forcing. The thermally enhanced torque could drive the planet to the synchronous state in as short as a few 10<jats:sup>4</jats:sup> yr.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We use data for 6048 early-type galaxies (ETGs) from Galaxy Zoo 1 that have been cross-matched with the catalog of the MPA-JHU emission-line measurements for the Sloan Digital Sky Survey Data Release 7. We measure the metallicity of these ETGs by excluding various ionization sources, and study other properties as well. We use the optimal division line of <jats:italic>W</jats:italic>2–<jats:italic>W</jats:italic>3 = 2.5 as a diagnostic tool, and for the first time derive metallicity measurements for 2218 ETGs. We find that these ETGs actually are closer to H <jats:sc>ii</jats:sc> regions as defined by Kauffmann et al. in the Baldwin–Philips–Terevich diagram, and they display younger stellar populations. We present a full mass–metallicity relation and find that most ETGs have lower metallicities than star-forming galaxies (SFGs) at a given galaxy stellar mass. We use five metallicity calibrators to check our results. We find that these metallicity indicators (R23, O32, and O3S2) give consistent results. We suggest that the remaining two metallicity calibrators, which increase metallicity by N<jats:italic>-</jats:italic>enrichment, can be used to calibrate metallicities for SFGs, but not to estimate the metallicities of ETGs.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Magnetic perturbations characterize the solar wind interaction of the Moon. The solar wind plasma absorption on the dayside surface produces large-scale field perturbations behind, i.e., the field enhancement in the central wake and reduction on the wake boundary. The solar wind repellence over local lunar magnetic anomalies (LMAs) leads to small-scale magnetic compressions ahead. In this study, the magnetic perturbations around the Moon are examined by using the observations from a near-Moon satellite mission, the Lunar Prospector, and they exhibit a clear left–right asymmetry in a coordinate system related to the solar wind convection electric field (<jats:inline-formula> <jats:tex-math> <?CDATA ${{\boldsymbol{E}}}_{\mathrm{SW}}$?> </jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjlab8640ieqn1.gif" xlink:type="simple" /> </jats:inline-formula>). The magnetic field is observed to enhance before the left terminator that <jats:inline-formula> <jats:tex-math> <?CDATA ${{\boldsymbol{E}}}_{\mathrm{SW}}$?> </jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjlab8640ieqn2.gif" xlink:type="simple" /> </jats:inline-formula> points to, while on the opposite side, it is not. The test particle simulations show that <jats:inline-formula> <jats:tex-math> <?CDATA ${{\boldsymbol{E}}}_{\mathrm{SW}}$?> </jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjlab8640ieqn3.gif" xlink:type="simple" /> </jats:inline-formula> can divert the particles reflected over the LMAs to the left and then the solar wind pickup of these particles leads to the field enhancement observed before the left terminator. Behind the lunar terminator, the wake field reduction is also asymmetric. On the left, the field reduction is more remarkable and located closer to the central wake. The denser plasma, consisting of the background as well as the reflected solar wind particles, may produce a stronger diamagnetic current and thus more significant field reduction there. The asymmetric plasma and magnetic perturbations associated with the reflected particles may be a common and nonnegligible element during the solar wind interaction of a small-scale magnetic field, such as that of an asteroid or a comet.</jats:p>