Discovery of a new group of double-periodic RR Lyrae stars in the OGLE-IV photometry

Abstract

We report the discovery of a new group of double-periodic RR Lyrae stars from the analysis of the OGLE-IV Galactic bulge photometry. In 11 stars identified in the OGLE catalog as first overtone pulsators (RRc stars) we detect additional longer period variability of low amplitude, in the mmag regime. One additional star of the same type is identified in a published analysis of the Kepler space photometry. The period ratio between the shorter first overtone period and a new, longer period lies in a narrow range around 0.686. Thus, the additional period is longer than the expected period of the undetected radial fundamental mode. The obvious conclusion that addition periodicity corresponds to a gravity or a mixed mode faces difficulties, however.

5 pages, 4 figures, accepted for publication in MNRAS Letters

References in corpus (5)

• Kepler photometry of RRc stars: peculiar double-mode pulsations and period doubling
• Revisiting CoRoT RR Lyrae stars: detection of period doubling and temporal variation of additional frequencies
• Blazhko-type modulation in the double-mode RR Lyrae stars of the OGLE Galactic bulge collection
• Double-mode radial-non-radial RR Lyrae stars in the OGLE photometry of the Galactic bulge
• On the modulation of RR Lyrae stars in the globular cluster M3

Cited by in corpus (14)

• First results on RR Lyrae stars with the TESS space telescope: untangling the connections between mode content, colors and distances
• Peculiar double-periodic pulsation in RR Lyrae stars of the OGLE collection. I. Long-period stars with dominant radial fundamental mode
• Peculiar double-periodic pulsation in RR Lyrae stars of the OGLE collection. II. Short-period stars with dominant radial fundamental mode
• Frequency analysis of OGLE-IV photometry for classical Cepheids in Galactic fields: non-radial modes and modulations
• Frequency analysis of the first-overtone RR Lyrae stars based on the Extended Aperture Photometry from the K2 data
• Time series analysis of bright TESS RRc stars: Additional modes, phase variations and more
• First Overtone Cepheids of the OGLE Magellanic Cloud Collection -- beyond radial modes
• Spectroscopic and photometric time series of the bright RRc star T Sex
• To Grow Old and Peculiar: A Survey of Anomalous Variable Stars in M80 and Age Determination using K2 and Gaia
• Detection of Gravity Modes in RR Lyrae Stars
• On the incidence rate of RR Lyrae stars with non-radial modes
• The VELOCE Modulation Zoo I. Spectroscopic detection of non-radial modes in the first-overtone Cepheids BG Crucis, QZ Normae, V0391 Normae, and V0411 Lacertae
• Matching seismic masses for RR Lyrae-type and oscillating red horizontal-branch stars in M4
• The VELOCE modulation zoo III. Detecting additional pulsation modes in optical spectra of classical Cepheids using semi-partial distance correlation periodograms