CHEOPS observations of HD 139139

The shallow depth of the events (~200ppm -- equivalent to transiting objects with radii of ~1.5R_{sun}_ in front of a Sun-like star), and their non- periodicity, constitutes a challenge for the photometric follow-up of this star. The goal of this study is to confirm with independent measurements the presence of shallow, non-periodic transit-like features on this object.

We performed observations with CHEOPS, for a total accumulated time of 12.75d, distributed in visits of roughly 20h in two observing campaigns in years 2021 and 2022. The precision of the data is sufficient to detect 150 ppm features with durations longer than 1.5h. We use the duration and times of the events seen in the K2 curve to estimate how many should have been detected in our campaigns, under the assumption that their behaviour during the CHEOPS observations would be the same as in the K2 data of 2017.