Thinkshop 16

The rotation periods of cool stars: Measurements, uses, connections and prospects

23rd - 26th September 2019

Talk

The effect of metallicity on the detectability of rotational periods in Sun-like stars

Veronika Witzke, Max Planck Institute for Solar System Research

The accurate determination of stellar rotation periods is important for estimating stellar ages as well as for understanding stellar activity and evolution. While for many stars rotation periods can be determined, there is an immense amount of stars, especially with low photometric variability or irregular pattern of variability, for which rotational periods are unknown. Here, we investigate the connection between the detectability of rotational periods and the metallicity for Sun-like stars using Kepler data. To analyse the influence of the metallicity on the detectability of the rotation periods, we select Sun-like stars with detected rotational periods, and without a significant period detection from McQuillan et al. (2014). We focus on stars with effective temperatures in the range 5600-5900 K, and surface gravities log g > 4.2, where for stars with known periods we further restrict the sample to rotation periods in the range of 24 - 30 days. For these sample we analyse the detection fraction of rotational periods for Sun-like stars with metallicity between M/H = -0.4 and M/H = 0.4. We find a dearth of periodic stars with near-solar rotation period and metallicity. The observational trends are explained using a stellar brightness variations model that accounts separately for spots and facular flux contributions. Varying the metallicity mostly changes the facular contrast, leading to an increased detectability of rotational periods for metallicities sufficiently different from the solar value.