The Rotation Period of the Planet-Hosting Star HD 189733

TL;DR

This study refines the stellar rotation period of HD 189733 using extended optical photometry, confirming the alignment between the star's rotation axis and the planet's orbital axis, which is crucial for understanding star-planet interactions.

Contribution

The paper provides a significantly more precise measurement of HD 189733's rotation period and estimates the inclination of its rotation axis, enhancing understanding of star-planet alignment.

Findings

Refined stellar rotation period to 11.953 days

Estimated stellar rotation axis inclination at least 56 degrees

Confirmed alignment between stellar spin and planetary orbit

Abstract

We present synoptic optical photometry of HD 189733, the chromospherically active parent star of one of the most intensively studied exoplanets. We have significantly extended the timespan of our previously reported observations and refined the estimate of the stellar rotation period by more than an order of magnitude: $P = 11.953\pm 0.009$ days. We derive a lower limit on the inclination of the stellar rotation axis of $56\arcdeg$ (with 95% confidence), corroborating earlier evidence that the stellar spin axis and planetary orbital axis are well aligned.