Rr lyrae stars as probes of structure in the milky way galaxy: tools and applicatións

Abstract

We present a compendium of two works regarding computational approach to RR Lyrae in surveys. We believe that improving programming skills and statistical knowledge is fundamental to tackle the challengesthat future surveys like GAlA and LSST will bring. In this sen se, we presenta set of tools that will result useful to get the better science from RR Lyrae and variable stars in general from the huge amountsof data that will be available when the next survey generation starts. In particular, we first present a theoretical calibration of the metallicity and physical parameters (temperature, luminosity, gravity, mass,radius) for RR Lyrae stars using the ugriz SDSS photometric system in the form of tight analytical fits that makes use of photometric data only. These fits are based on calculations of synthetic horizontalbranches and are able to provide all the quantities mentioned with very high (internal) precision. Second, we present algorithms and techniques to extract RRab stars from the southern part of the CatalinaSurveys. We developed two algorithms, Automatic Period Selection (APS) and Automatic Fourier Decomposition (AFD), to find better period and Iightcurves from V band photometric data. With the APSoutput we classified 10541 RRab stars in an area that covers more than 14800 square degrees in the declination range of-75° < σ < - 15°. The se1ected samp1e is provided with photometric metallicities, unreddened distances and ga1actocentric positions. We performed an automatic study of the overdensities on the southern part of the halo finding 49 overdensity candidates with significances as high as 10σ compared to halo models.