Cepheid investigations using the Kepler space telescope

TL;DR

This study confirms V1154 Cyg as a fundamental mode Cepheid using Kepler data, and characterizes other candidates, demonstrating Kepler's precision in stellar variability analysis.

Contribution

First Kepler-based confirmation of a Cepheid star and detailed analysis of candidate stars' variability types.

Findings

V1154 Cyg is a fundamental mode Cepheid.

Kepler data shows no nonradial or stochastic modes at micromagnitude level.

Other candidates are spotted stars, eclipsing systems, or flare stars.

Abstract

We report results of initial work done on selected candidate Cepheids to be observed with the Kepler space telescope. Prior to the launch 40 candidates were selected from previous surveys and databases. The analysis of the first 322 days of Kepler photometry, and recent ground-based follow-up multicolour photometry and spectroscopy allowed us to confirm that one of these stars, V1154 Cyg (KIC 7548061), is indeed a 4.9-d Cepheid. Using the phase lag method we show that this star pulsates in the fundamental mode. New radial velocity data are consistent with previous measurements, suggesting that a long-period binary component is unlikely. No evidence is seen in the ultra-precise, nearly uninterrupted Kepler photometry for nonradial or stochastically excited modes at the micromagnitude level. The other candidates are not Cepheids but an interesting mix of possible spotted stars, eclipsing systems and flare stars.