SIMBAD references

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.