Examinando por Autor "Contreras-Ramos, Rodrigo"
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Ítem A machine learned classifier for RR Lyrae in the VVV survey(EDP Sciences, 2016-11) Elorrieta, Felipe; Eyheramendy, Susana; Jordán, Andrés; Dékány, István; Catelan, Márcio; Angeloni, Rodolfo; Alonso-García, Javier; Contreras-Ramos, Rodrigo; Gran, Felipe; Hajdu, Gergely; Espinoza, Néstor; Saito, Roberto K.; Minniti, DanteVariable stars of RR Lyrae type are a prime tool with which to obtain distances to old stellar populations in the Milky Way. One of the main aims of the Vista Variables in the Via Lactea (VVV) near-infrared survey is to use them to map the structure of the Galactic Bulge. Owing to the large number of expected sources, this requires an automated mechanism for selecting RR Lyrae, and particularly those of the more easily recognized type ab (i.e., fundamental-mode pulsators), from the 106−107 variables expected in the VVV survey area. In this work we describe a supervised machine-learned classifier constructed for assigning a score to a Ks-band VVV light curve that indicates its likelihood of being ab-type RR Lyrae. We describe the key steps in the construction of the classifier, which were the choice of features, training set, selection of aperture, and family of classifiers. We find that the AdaBoost family of classifiers give consistently the best performance for our problem, and obtain a classifier based on the AdaBoost algorithm that achieves a harmonic mean between false positives and false negatives of ≈7% for typical VVV light-curve sets. This performance is estimated using cross-validation and through the comparison to two independent datasets that were classified by human experts.Ítem VVV Survey Microlensing: The Galactic Longitude Dependence(Institute of Physics Publishing, 2018-09) Navarro, María Gabriela; Minniti, Dante; Contreras-Ramos, RodrigoWe completed the search for microlensing events in the zero latitude area of the Galactic bulge using the VVV Survey near-infrared (near-IR) data obtained between 2010 and 2015. We have now a total sample of N = 630 events Using the near-IR color-magnitude diagram we selected the red clump (RC) sources to analyze the longitude dependence of microlensing across the central region of the Galactic plane. The events show a homogeneous distribution, smoothly increasing in numbers toward the Galactic center, as predicted by different models. We find a slight asymmetry, with a larger number of events toward negative longitudes than positive longitudes. This asymmetry is seen both in the complete sample and the subsample of RC giant sources, and it is possibly related with the inclination of the bar along the line of sight. The timescale distribution is fairly symmetric with a peak in 17.4 ±1.0 days for the complete sample (N = 630 events), and 20.7 ±1.0 days for the RC stars (N = 291 events), in agreement with previous results. © 2018. The American Astronomical Society. All rights reserved.