Multiperiodic RR Lyrae stars in the center of the Galaxy

Abstract

This paper presents results of a fully automated search for multiperiodic RR Lyrae stars in the center of the Galaxy. The search was carried out on OGLE-II database created by means of image subtraction method. I found more than 2700 RR Lyrae stars with about 600 showing various kinds of multiperiodic behavior. Previous OGLE-I database contained only about 200 RR Lyrae stars in the Galactic Bulge, that is twelve times less than the current sample. There are two most interesting outcomes for Bulge: very high percentage of Blazhko stars and very low percentage of RRd stars. Blazhko effect was confirmed in about 25 percent of all RRab stars. This incidence rate is almost 2.5 times greater than in the Large Magellanic Cloud. On the other hand I discovered only 3 RRd stars, which implies that the incidence rate of this type of variables is much smaller in Bulge than in the Magellanic Clouds.