Timescales of starspot variability in slow rotators

¹ Space Research Institute, Institut für Weltraumforschung (IWF), Austrian Academy of Sciences, Schmiedlstrasse 6, 8042 Graz, Austria
e-mail: oleksiy.arkhypov@oeaw.ac.at
² Skobeltsyn Institute of Nuclear Physics, Moscow State University, 119992 Moscow, Russia
³ Institute for Astronomy (IfA), University of Vienna, Türkenschanzstrasse 17, 1180 Vienna, Austria
e-mail: manuel.guedel@univie.ac.at
⁴ Karl-Franzens-Universität Graz (KFUG), 8010 Graz, Austria

Received: 3 October 2017
Accepted: 15 February 2018

Abstract

There is an intriguing proximity between the turnover time τ_MLT of the standard mixing length theory of the Sun and the timescale τ_lam of solar activity patterns at the space scale of giant laminar convection assumed in deep layers of the Sun. To verify the reliability of this correspondence, we analyzed the light curves of 637 slowly rotating stars, observed by the Kepler mission, with periods from 16 to 30 days. The proximity τ_MLT ≈ τ_lam is confirmed. The performed study also confirms the manifestation of large scale turbulence in the dynamics of surface activity such as that in the Sun. These results open a new way to measure the key astrophysical parameter τ_MLT and to study deep convection that has been undetected with asteroseismology.