The dependence of maximum starspot amplitude and the amplitude distribution on stellar properties

Abstract

We combine photometric data from field stars, plus over a dozen open clusters and associations, to explore how the maximum photometric amplitude (Amax) and the distribution of amplitudes varies with stellar properties. We find a complex variation of Amax with inverse Rossby number Ro-1, which nevertheless can be modeled well with a simple model including an increase in Amax with rotation for low Ro-1, and a maximum level. Amax may then be further affected by differential rotation and a decline at the highest Ro-1. The distribution of Aspot below Amax varies with Ro-1: it peaks at low Aspot with a long tail towards Amax for low Ro-1, but is more uniformly distributed at higher Ro -1. We investigate further dependences of the Aspot distributions on stellar properties, and speculate on the source of these variations. © International Astronomical Union 2011.