Results of a Search for gamma Dor and delta Sct Stars with the Kepler Spacecraft

TL;DR

This study analyzed light curves of 2768 stars from Kepler data to identify gamma Doradus, delta Scuti, and hybrid pulsators, expanding the understanding of stellar oscillations in stars slightly more massive than the Sun.

Contribution

It provides a uniform analysis of Kepler data leading to the discovery of 323 candidate pulsating stars across different classes, many of which challenge previous ground-based instability strip boundaries.

Findings

Identified 207 gamma Doradus, 84 delta Scuti, and 32 hybrid candidates.

Many candidates are cooler than previously known instability strips.

Few variable stars are fainter than magnitude 15, possibly due to galactic distribution.

Abstract

The light curves of 2768 stars with effective temperatures and surface gravities placing them near the gamma Doradus/delta Scuti instability region were observed as part of the Kepler Guest Observer program from Cycles 1 through 5. The light curves were analyzed in a uniform manner to search for gamma Doradus, delta Scuti, and hybrid star pulsations. The gamma Doradus, delta Scuti, and hybrid star pulsations extend asteroseismology to stars slightly more massive (1.4 to 2.5 solar masses) than our Sun. We find 207 gamma Doradus, 84 delta Scuti, and 32 hybrid candidate stars. Many of these stars are cooler than the red edge of the gamma Doradus instability strip as determined from ground-based observations made before Kepler. A few of our gamma Doradus candidate stars lie on the hot side of the ground-based gamma Doradus instability strip. The hybrid candidate stars cover the entire region between 6200 K and the blue edge of the ground-based delta Scuti instability strip. None of our candidate stars are hotter than the hot edge of the ground-based delta Scuti instability strip. Our discoveries, coupled with the work of others, shows that Kepler has discovered over 2000 gamma Doradus, delta Scuti, and hybrid star candidates in the 116 square degree Kepler field of view. We found relatively few variable stars fainter than magnitude 15, which may be because they are far enough away to lie between spiral arms in our Galaxy, where there would be fewer stars.