Large Starspot Groups on HAT-P-11 in Activity Cycle 1

TL;DR

This study reports ground-based photometry of HAT-P-11, revealing extensive starspot coverage during its activity cycle, indicating the emergence of large spot groups at the cycle's start, enhancing understanding of stellar magnetic activity.

Contribution

First ground-based measurement of starspot coverage on HAT-P-11 during its activity cycle, identifying large spot groups at cycle onset.

Findings

Starspot coverage of 14% in a specific transit.

This transit is the most spotted observed on HAT-P-11.

Likely observation of large spot groups at cycle start.

Abstract

HAT-P-11 is a planet-hosting K4V star in the Kepler field, with an activity cycle that bear similarities to the Sun's. The chromospheric activity of HAT-P-11 indicates that a new activity cycle is beginning. We report ground-based observations with holographic diffuser photometry to measure the starspots of HAT-P-11 in its second observed magnetic activity cycle (Cycle 1). We find the area coverage of starspots within the transit chord for UTC 2017-10-30 is 14% --- which makes this transit the most spotted HAT-P-11 transit observed to date. We suggest that we are likely observing occultations of large spot groups appearing at the beginning of Cycle 1.