Examinando por Autor "Minniti, D.|q(Dante),|d1962-"

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    Blue horizontal branch stars using the VVV survey
    (Universidad Andrés Bello, 2018) Montenegro Armijo, Katherine Macarena; Minniti, D.|q(Dante),|d1962-; Facultad de Ciencias Exactas
    The VISTA Variables in the V a L actea (VVV) is an ESO Public Survey, part of the Paranal Observatory. The VVV Survey is targeting the central parts of our galaxy, covering an area of 540 square degrees. Its main goal is to study our galaxy's bulge and southern plane, in order to reveal the corresponding 3D structure through variable stars. This survey detects the emission of stars in ve near-IR bands (ZYJHKs), and uses it to solve the problem of high interstellar dust extinction and high stellar density in that area. In this thesis project, we aim to search and characterize the population of Blue Horizontal Branch (BHB) stars, taking a census of these old and numerous objects in the bulge-halo transition region of the Milky Way, which corresponds to the VVV tiles b201 - b228 (10o & ` & 350o and 􀀀10o . b . 􀀀8o). Using the globular cluster M22 as a standard and constructing colorcolor diagrams with speci c cuts in color, we were able to nd our targets. According to this, a total of 12554 BHB stars were detected. In order to detect and characterize overdensities of stars in sizes similar to those of old clusters or streams, Montecarlo simulations were performed. The main simulation was made using the same number of stars that the total of tiles contain. More simulations were made for each of the 28 tiles and their respective stars. By plotting and comparing real and simulated data, and using the appropiate bin size, we detected some overdensities, mostly of low signi cance. Using data from VSA (VISTA Science Archive) and doing a crossmatch with our targets, we constructed lightcurves for BHB stars to study their variability properties in the Ks band. We took an average of 52 epochs to calculate periods and amplitudes, and also identi ed eclipsing binaries that were present in our data. We obtained a total of 7665 variable star lightcurves with an average period of 0.53 [days], of which 336 correspond to bonadife eclipsing binaries. These results allow comparisons with other old stellar populations such as RR Lyrae variable stars.