The detection of a second radial mode in the RR Lyr type star puts strong constrain on its internal structure. We present 59 new Galactic double mode RR Lyr stars found in the LINEAR survey data with the fundamental radial mode and the ﬁrst overtone exited (RRd stars). These stars may be useful for constraining the mass-metallicity relation for ﬁeld horizontal branch stars. We present the updated Petersen diagram and the distribution of the fundamental mode periods in the Galactic RRd stars.
Author: R. Poleski