C14 Automatic Imaging Telescope Photometry of GJ1214

Abstract

GJ1214b is the highest signal-to-noise sub-Neptune for atmospheric studies. Although most previous transmission spectroscopy measurements have revealed a frustratingly featureless spectrum, JWST observations are expected to give new insights to this benchmark planet. We have performed photometric monitoring of GJ1214 (the host star) to provide context for these observations. We find that GJ1214 entered a period of relatively high brightness during 2021 and 2022. This implies that the JWST MIRI/LRS phase curve observation of GJ1214b in July 2022 was obtained during an epoch of low activity for the spot-dominated host star. Like previous works, we are unable to definitively identify the star's rotation period. Nevertheless, we confirm that it is likely >50 days.