Do We Know of Any Maunder Minimum Stars?

Abstract

Most stars previously identified as Maunder minimum stars are old and evolved off the main sequence. Analysis of activity measurements from the California and Carnegie Planet Search program stars and Hipparcos parallaxes implies that the canonical relation between age and chromospheric activity breaks down for stars older than ~6 Gyr when activity is calculated from Mount Wilson S-values. Stars only 1 mag above the main sequence exhibit significantly suppressed activity levels, which have been mistaken for examples of Maunder minimum behavior.

Based on observations obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration. The Keck Observatory was made possible by the generous financial support of the W. M. Keck Foundation.