USNO-B1.0 1171-0309158: An RR Lyrae Star that Switched from a Double- to Single-mode Pulsation

TL;DR

This paper reports the discovery of an RR Lyrae star that transitioned from double-mode to single-mode pulsation, providing insights into pulsation mode switching in variable stars.

Contribution

It presents the first observed case of an RR Lyrae star changing its pulsation mode from double to single mode, based on Catalina survey data and follow-up CCD observations.

Findings

Star switched from double-mode to single-mode pulsation.

Gradual increase in scattering and amplitude observed before mode change.

No first-overtone pulsation detected in 2015 observations.

Abstract

We report the discovery of a new case of an RR Lyrae star that experienced a switching of its pulsation mode. We detected USNO-B1.0 1171-0309158 as a double-mode RR Lyrae star from observations of the Catalina surveys (CSS) that showed additional scattering on the light curve. Our analysis of the time-series of CSS data showed gradual increase in scattering and in the amplitude of fundamental pulsation mode. Our CCD observations carried out in 2015 reveal that this object is now a fundamental-mode RRab star, with no sign of the first-overtone pulsation.