English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

During the solar magnetic activity cycle the emergence latitudes of sunspotschange, leading to the well-known butterfly diagram. This phenomenon is poorlyunderstood for other stars as starspot latitudes are generally unknown. Therelated changes in starspot rotation rates caused by latitudinal differentialrotation can however be measured. Using the set of 3093 Kepler stars withactivity cycles identified by Reinhold et al. (2017), we aim to study thetemporal change in starspot rotation rates over magnetic activity cycles, andhow this relates to the activity level, mean rotation rate, and effectivetemperature of the star. We measure the photometric variability as a proxy forthe magnetic activity and the spot rotation rate in each quarter over theduration of the Kepler mission. We phase-fold these measurements with the cycleperiod. We perform averages over stars with comparable mean rotation rates andeffective temperature at fixed activity-cycle phases. We detect a clearcorrelation between the variation of activity level and the variation of thestarspot rotation rate. The sign and amplitude of this correlation depends onthe mean stellar rotation and, to a lesser extent, on the effectivetemperature. For slowly rotating stars (with periods between 15-28 days) thestarspot rotation rates are clearly anti-correlated with the level of activityduring the activity cycles. A transition is seen at periods of 10-15 days,where stars with effective temperature above 4200K instead show positivecorrelation. Our results can be interpreted in terms of a stellar "butterflydiagram", but these appear different from the Sun's as the starspot rotationrates are either in phase or anti-phase with the activity level. Alternatively,the activity cycles seen by Kepler are short (around 2.5 years) and maytherefore be secondary cycles, perhaps analogous to the solar quasi-biennialoscillations.

Starspot rotation rates vs. activity cycle phase: Butterfly diagrams of Kepler stars are unlike the Sun's