Catálogo de publicaciones - revistas

<jats:title>Abstract</jats:title> <jats:p>0.47–2.45 <jats:italic>μ</jats:italic>m spectroscopy is reported for the compact planetary nebula Minkowski 4-18 (PK146+07), filling some spectral gaps and presenting uniform and simultaneous observation of this entire spectral range. While the strongest features are the H <jats:sc>i</jats:sc> lines, the most prevalent are those of carbon, principally of C <jats:sc>ii</jats:sc>, commensurate with the carbon rich, Wolf–Rayet nature of the exciting star.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>K2-138 d (EPIC 245950175 d) is one of five planets in a chain of 3:2 mean motion resonances discovered by Christiansen et al. in K2 Campaign 12. An additional planet, confirmed with the Spitzer Space Telescope by Hardegree-Ullman et al., is not in the resonant chain. The near first-order resonances, coupled with the planets being locked in a set of three-body Laplace resonances, make this system a unique target to study for transit timing variations (TTVs). As the predicted transit timing amplitude (∼7 minutes) was below the typical transit timing uncertainty (∼10 minutes) of the K2 data, Christiansen et al. were unable to detect TTVs for K2-138 d in the K2 time series. Here, we describe new observations that allow us to refine the ephemeris for K2-138 d and perform a brief search for TTVs. Our efforts result in a refined orbital period that is 19 times more precise than previously available measurements, but our data are insufficient to confirm a TTV signal for K2-138 d.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The gradient of the gravitational redshift in the potential of the Milky Way induces an apparent spurious radial migration. I show that this effect is simply related to the local acceleration, which was measured recently by Gaia eDR3, implying a spectroscopic shift of −2.4 × 10<jats:sup>−2</jats:sup>(<jats:italic>r</jats:italic>/8 kpc)<jats:sup>−1</jats:sup> km s<jats:sup>−1</jats:sup> kpc<jats:sup>−1</jats:sup>. The transverse Doppler effect yields a comparable contribution. The spurious radial velocity from both relativistic effects amounts to crossing a major portion of the Milky Way disk during the age of the universe, and must be corrected for in any future measurement of the actual radial migration of stars.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>I show that General Relativity sets an absolute upper limit on the energy flux observed from a cosmological source as a function of its redshift. Detecting a brighter source in gravitational waves, neutrinos or light, would flag new physics. The derived flux limit can also be used to determine the maximum redshift possible for any source with an unknown origin.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>In this first of two studies, we apply a random forest model to classify ultracool dwarfs from broadband color information. Using the Skrzypek et al. ultracool dwarf sample and a set of background sources, we trained a random forest classifier based on 28 colors derived from optical and infrared photometry from SDSS, UKIDSS, and WISE. Our model achieves 99.7% accuracy in segregating L- and T-type UCDs from background sources, and 97% accuracy in separating spectral subgroups. A separate random forest regressor model achieved a spectral classification precision of 1.3 subtypes. We applied these models to a 12.6 deg<jats:sup>2</jats:sup> region with overlapping SDSS, UKIDSS, and WISE coverage and identified 35 UCD candidates, five of which are previously reported, of which four are photometrically or spectroscopically classified UCDs. Our random forest model can be applied to multiple surveys to greatly expand the known census of UCDs.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We evaluate color-based classifiers in a synthesis of Pan-STARRS, 2MASS, UKIDSS, and AllWISE catalogs to identify ultracool dwarfs (UCDs). Using the Best et al. compilation of UCDs and a sample of background sources as our training set, we constructed a two-tier random forest model to segregate UCDs from non-UCDs and sort them into spectral subgroups. We also developed a regressor model to infer numerical classifications. Our classifier models achieved accuracies of 97%–99%, while our regressor model achieved a classification accuracy of 0.64 subtypes for classifications M5–T8. We applied these models to a 7 deg<jats:sup>2</jats:sup> region with overlapping survey data and identified 336 UCD candidates, of which 26 are previously identified UCDs and 17 are extragalactic sources.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The Transiting Exoplanet Survey Satellite (TESS) observed a single transit of the giant exoplanet TOI-2180 b in Sector 19 of its primary mission. A subsequent effort to characterize this system found that the orbital period of TOI-2180 b is 260.8 ± 0.6 days. This level of precision precludes most efforts to detect future transits and to further understand this exoplanet. We present a new transit of TOI-2180 b observed by TESS in Sector 48 and update the planet’s transit ephemeris with its precisely measured orbital period. The refined ephemeris enables future transit observations to explore this planet’s atmosphere or to search for rings or moons.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The simplistic but ubiquitous Mixing Length Theory (MLT) formalism is used to model convective energy transport within 1D stellar evolution calculations. The formalism relies on the free parameter <jats:italic>α</jats:italic> <jats:sub>MLT</jats:sub>, which must be independently calibrated within each stellar evolution program and for any given set of physical assumptions. We present a solar calibration of <jats:italic>α</jats:italic> <jats:sub>MLT</jats:sub> appropriate for use with the ÆSOPUS opacities, which have recently been made available for use with the MESA stellar evolution software. We report a calibrated value of <jats:italic>α</jats:italic> <jats:sub>MLT</jats:sub> = 1.931 and demonstrate the impact of using an appropriately calibrated value in simulations of a 3<jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub> asymptotic giant branch star.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Consideration is given to the stellar metallicity distribution that would result from a hypothetical dissociation of all Milky Way globular clusters into field stars, and several characteristics are compared to an exponential distribution.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>This paper explores the long-term stability of six Neptunian Trojans. In contrast with other Neptunian Trojans, these objects have previously unknown lifetimes and larger orbital uncertainties due to their shorter observational arcs. We obtained new astrometry of the six Trojans using the Magellan telescope, refit their orbits, and performed Gyr-long numerical integrations to estimate their lifetimes. The results show that five of these six objects are stable over Gyr timescales. The remaining object, 2015 VV<jats:sub>165</jats:sub>, has a calculated lifetime of 0.691 ± 0.001 Gyr, which is similar to the previous estimate of 0.65 Gyr. As a result, the shorter lifetime of this latter object is most likely physical (rather than due to uncertainties in its orbital determination).</jats:p>