Non-radial Pulsations in RR Lyrae Stars from the OGLE Collection

TL;DR

This study analyzes a large collection of RR Lyrae stars from OGLE, discovering new non-radial pulsation modes and expanding the known population of double-mode RR Lyrae stars with unique period ratios.

Contribution

The paper reports the discovery of new non-radial pulsation modes in RR Lyrae stars and significantly increases the known number of such stars with specific period ratios.

Findings

Identified new non-radial pulsation modes in RR Lyrae stars.

Increased known RR Lyrae stars of this type by a factor of 8.

Discovered a new group of double-mode RR Lyrae stars with period ratio around 0.686.

Abstract

RR Lyrae stars are classical pulsating stars. They pulsate mostly in the radial fundamental mode (RRab stars), in the radial first overtone mode (RRc stars), or in both modes simultaneously (RRd stars). Collection of variable stars from the Optical Gravitational Lensing Experiment (OGLE) contains more than 38 000 RR Lyrae stars from the Galactic bulge. We analysed these data for RRc and RRd stars. We have found new members of radial-non-radial double-mode RR Lyrae stars, with characteristic period ratio of the two modes around 0.61. We increased the number of known RR Lyrae stars of this type by a factor of 8. We have also discovered another group of double-mode RR Lyrae stars. They pulsate in the first overtone and in another, unidentified mode, which has period longer than period of the undetected fundamental mode. The period ratios tightly cluster around 0.686. These proceedings are focused on this puzzling group. In particular, we report eight new members of the group.