The Starspots of HAT-P-11: Evidence for a Solar-like Dynamo

TL;DR

This study analyzes starspots on HAT-P-11, revealing a latitude and size distribution similar to solar sunspots during maximum activity, suggesting a solar-like dynamo process.

Contribution

It provides the first detailed comparison of starspot size and latitude distribution on HAT-P-11 with solar sunspots, indicating a solar-like magnetic activity cycle.

Findings

Starspots are distributed in latitude like sunspots near solar maximum.

Most starspots have sizes similar to sunspots at solar maximum.

Estimated spotted area coverage is about 3%, much higher than the Sun.

Abstract

We measure the starspot radii and latitude distribution on the K4 dwarf HAT-P-11 from Kepler short-cadence photometry. We take advantage of starspot occultations by its highly-misaligned planet to compare the spot size and latitude distributions to those of sunspots. We find that the spots of HAT-P-11 are distributed in latitude much like sunspots near solar activity maximum, with mean spot latitude of $16 \pm 1$ degrees. The majority of starspots of HAT-P-11 have physical sizes that closely resemble the sizes of sunspots at solar maximum. We estimate the mean spotted area coverage on HAT-P-11 is $3^{+6}_{-1}\%$, roughly two orders of magnitude greater than the typical solar spotted area.