Title of programme: Pinning down a young planetary system: CHEOPS observations of AU Mic (CHAUMic)
Abstract: We propose to carry out an intensive, in-transit and out-of-transit, CHEOPS observing campaign of the golden target AU Mic aiming at: • constraining the TTV signals of AU Mic b and c, and measuring their masses. High-precision radial velocity observations of AU Mic are hampered by the activity of the star, as recently shown by Zicher et al. 2022 (MNRAS, 512, 3060), who measured the masses of planet b and c with a precision of “only” 43 % and 30 % using more than 100 HARPS measurements evenly spread across one year. Conversely, CHEOPS have proven to be very effective in measuring planet masses of near-resonant transiting systems, such as TOI-1130 b and c, for which a precision of ?9 % has been achieved exploiting the TTV method. Our program requires transit observations of planet b and c to be carried out in July, August. • studying the evolution time-scale of active regions across the transit cord using AU Mic b as a “scanner”. Unbiased measurements of Rp/R? can be determined only by modeling the transit light curves along with the map of the occulted (and unocculted, see below) spots. This requires CHEOPS multiple observations of the transits of AU Mic b at the 4 possible star-planet configurations. By observing spot-crossing events of transits occurring at the same stellar longitudes as in 2020 and 2021’s CHEOPS observations, we will also assess whether the distribution of spots has evolved or not. On the other hand, transit observations at stellar longitudes that have not yet been probed with CHEOPS, will allow us to explore the remaining “faces” of AU Mic. • deriving unbiased planetary radii by performing also a spot modelling of AU Mic. We will combine CHEOPS filler observations of AU Mic (1-2 orbits) performed at different rotation phases, with ongoing multi-band photometric monitoring carried out with the EULER telescope, and HARPS and CORALIE spectra to measure the spot-filling factor and the spot-to-photosphere temperature ratio. This will allow us correct for the effect of unocculted spots on the transit depth, improving the accuracy of the planet-to-star radius measurement of both planets.
Temporal Coverage
2022-08-27T10:19:52Z / 2022-08-27T11:59:00Z
Version
3.0
Mission Description
CHEOPS (Benz et al., https://doi.org/10.1007/s10686-020-09679-4) is a European Space Agency (ESA) mission in partnership with Switzerland with important contributions to the payload and the ground segment from Austria, Belgium, France, Germany, Hungary, Italy, Portugal, Spain, Sweden and the United Kingdom.
The satellite has a single payload comprising an ultra-high precision photometer covering the 330 - 1100 nm wavelength range in a single photometric band. Observations are made as part of the Guaranteed Time Observing Programme that is formulated by the CHEOPS Science Team, and the Guest Observers Programme through which the Community at large can apply for CHEOPS time.
