A detailed analysis of the Draco dSph variable stars

Abstract

The present work aims at updating, improving and expanding the current knowledge of Draco dSph galaxy variable stars population. We present the classification and analysis of a census of 267 variable stars based on their pulsational properties, light curves and positions in the color-magnitude diagram. We report 246 RR Lyrae (RRL) stars (200 RRab, 37 RRc and 9 RRd), 7 Anomalous Cepheids (AC) and 9 δ Scu star. Also, we identify 5 Long Period Variable (LPV) with insufficient data for a more in-depth analysis. Pulsational properties (period and amplitude) and mean magnitudes were calculated for the RRL, the ACs and the δ Scu stars. We used the properties of RRL stars to derive the distance to the Draco dSph using two different methods: the periodWesenheit relations and the Luminosity-Metallicity relations. An independent period-luminosity relation was used to derive the metallicity distribution of the RRL stars population. The properties of the ACs, thanks to the relations between period, magnitude and amplitude or colour, allowed us to determine their individual pulsation mode and masses. The 9 δ Scu stars are the first ones of this type of being identified in Draco. Finally, we provide a comparison between our results and previous works, specifically the one by [Kin+08].