Double-mode radial–non-radial RR Lyrae stars in the OGLE photometry of the Galactic bulge
Double-mode radial–non-radial RR Lyrae stars in the OGLE photometry of the Galactic bulge
Non-radial modes are excited in classical pulsators, both in Cepheids and in RR Lyrae stars. Firm evidence comes from the first-overtone pulsators, in which an additional shorter period mode is detected with characteristic period ratio falling between 0.60 and 0.65. For first-overtone Cepheids, three separate sequences populated by nearly 200 …