Photometric Variability in Kepler Target Stars: The Sun Among Stars -- A First Look

TL;DR

This study uses Kepler data to compare the photometric variability of the Sun with a large sample of stars, revealing that many stars are more active than the Sun, especially cooler stars.

Contribution

First analysis of Kepler's stellar lightcurves comparing solar variability to a broad range of stars with unprecedented precision.

Findings

Nearly half of the stars are more active than the Sun.

Most stars similar to the Sun are not more than twice as active.

Active fraction increases for cooler stars below mid K spectral types.

Abstract

The Kepler mission provides an exciting opportunity to study the lightcurves of stars with unprecedented precision and continuity of coverage. This is the first look at a large sample of stars with photometric data of a quality that has heretofore been only available for our Sun. It provides the first opportunity to compare the irradiance variations of our Sun to a large cohort of stars ranging from vary similar to rather different stellar properties, at a wide variety of ages. Although Kepler data is in an early phase of maturity, and we only analyze the first month of coverage, it is sufficient to garner the first meaningful measurements of our Sun's variability in the context of a large cohort of main sequence stars in the solar neighborhood. We find that nearly half of the full sample is more active than the active Sun, although most of them are not more than twice as active. The active fraction is closer to a third for the stars most similar to the Sun, and rises to well more than half for stars cooler than mid K spectral types.