The California Legacy Survey. V. Activity cycles

The California Legacy Survey stars are amenable to exoplanet detection using precise radial velocities, and we present their CaII H and K time series as a proxy for stellar and chromospheric activity. Using the High Resolution Echelle Spectrometer at Keck Observatory, we measured stellar flux in the cores of the CaII H and K lines to determine S-values on the Mount Wilson scale and the log(R_HK_^'^) metric, which is comparable across a wide range of spectral types.

From the 710 stars, with 52372 observations, 285 stars were sufficiently sampled to search for stellar activity cycles with periods of 2-25yr, and 138 stars showed stellar cycles of varying length and amplitude. S-values can be used to mitigate stellar activity in the detection and characterization of exoplanets. We used them to probe stellar dynamos and to place the Sun's magnetic activity into context among solar neighborhood stars.