Flavours of variability: 29 RR Lyrae stars observed with Kepler

TL;DR

This study analyzes 29 RR Lyrae stars observed with Kepler, revealing precise pulsation periods, Blazhko modulations, additional frequencies, and the first double mode pulsator among non-Blazhko stars, advancing understanding of stellar variability.

Contribution

The paper provides the first detailed Kepler-based analysis of a large sample of RR Lyrae stars, discovering new modulation behaviors and pulsation modes.

Findings

Precise pulsation periods for all 29 stars.

Detection of Blazhko modulations in 14 stars.

Identification of additional frequencies near harmonics and overtones.

Abstract

We present our analysis of Kepler observations of 29 RR Lyrae stars, based on 138-d of observation. We report precise pulsation periods for all stars. Nine of these stars had incorrect or unknown periods in the literature. Fourteen of the stars exhibit both amplitude and phase Blazhko modulations, with Blazhko periods ranging from 27.7 to more than 200 days. For V445 Lyr, a longer secondary variation is also observed in addition to its 53.2-d Blazhko period. The unprecedented precision of the Kepler photometry has led to the discovery of the the smallest modulations detected so far. Moreover, additional frequencies beyond the well-known harmonics and Blazhko multiplets have been found. These frequencies are located around the half-integer multiples of the main pulsation frequency for at least three stars. In four stars, these frequencies are close to the first and/or second overtone modes. The amplitudes of these periodicities seem to vary over the Blazhko cycle. V350 Lyr, a non-Blazhko star in our sample, is the first example of a double mode RR Lyrae star that pulsates in its fundamental and second overtone modes.