Transit timing variations of AU Microscopii b and c

TL;DR

This paper reports significant transit timing variations in the AU Microscopii b and c exoplanets, indicating strong mutual gravitational interactions in this young planetary system, with implications for understanding planetary dynamics.

Contribution

It provides the first combined analysis of TESS and CHEOPS data revealing large TTVs and predicts future transit timing deviations due to planetary perturbations.

Findings

Detected ~23-minute TTV span between extrema.

Predicted 30-85 minute delays in 2022 transits.

Confirmed mutual perturbations as cause of TTVs.

Abstract

Here we report large-amplitude transit timing variations (TTVs) for AU\,Microcopii b and c as detected in combined TESS (2018, 2020) and CHEOPS (2020, 2021) transit observations. AU Mic is a young planetary system with a debris disk and two transiting warm Neptunes. A TTV on the order of several minutes was previously reported for AU Mic b, which was suggested to be an outcome of mutual perturbations between the planets in the system. In 2021, we observed AU Mic b (five transits) and c (three transits) with the CHEOPS space telescope to follow-up the TTV of AU Mic b and possibly detect a TTV for AU Mic c. When analyzing TESS and CHEOPS 2020--2021 measurements together, we find that a prominent TTV emerges with a full span of ~23 minutes between the two TTV extrema. Assuming that the period change results from a periodic process - such as mutual perturbations - we demonstrate that the times of transits in the summer of 2022 are expected to be 30--85 minutes later than predicted by the available linear ephemeris.