The Rotation Period of the Planet-Hosting Star HD 189733

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.