Rotation in the Pleiades with K2: II. Multi-Period Stars

TL;DR

This study analyzes multi-period rotation behaviors in Pleiades stars using K2 data, revealing complex patterns likely due to differential rotation and spot evolution, and categorizes these behaviors to understand stellar rotation dynamics.

Contribution

It introduces a detailed classification of multi-period behaviors in Pleiades stars based on K2 observations, advancing understanding of stellar rotation complexities.

Findings

24% of stars show multiple real frequencies in periodograms

Complex periodogram peaks are linked to spot evolution and differential rotation

Fast rotators predominantly exhibit single-period behavior, indicating solid-body rotation

Abstract

We use K2 to continue the exploration of the distribution of rotation periods in Pleiades that we began in Paper I. We have discovered complicated multi-period behavior in Pleiades stars using these K2 data, and we have grouped them into categories, which are the focal part of this paper. About 24% of the sample has multiple, real frequencies in the periodogram, sometimes manifesting as obvious beating in the light curves. Those having complex and/or structured periodogram peaks, unresolved multiple periods, and resolved close multiple periods are likely due to spot/spot group evolution and/or latitudinal differential rotation; these largely compose the slowly rotating sequence in $P$ vs.~$(V-K_{\rm s})_0$ identified in Paper I. The fast sequence in $P$ vs.~$(V-K_{\rm s})_0$ is dominated by single-period stars; these are likely to be rotating as solid bodies. Paper III continues the discussion, speculating about the origin and evolution of the period distribution in the Pleiades.