2087240

Target RA (J2000): 239.962296 and deg Target Dec (J2000): -28.06180 and deg Gaia GMag: 11.38 Programme ID: CH_PR230029 PI of observing programme: Saba Title of programme: Constraining Refractory Species and Characterising the Stellar Environment of the Inflated hot-Jupiter WASP-17 b Abstract: In the known population of exoplanets puffy hot-Jupiters are extremely rare and yet crucial in order to understand planetary formation and evolution. Their large radii coupled with the high S/N ratio achievable thanks to their extended atmospheres makes them the perfect target for current observational facilities. In this restricted pool of planets WASP-17b is an ideal case study. With an equilibrium temperature of ~1800 K this inflated hot-Jupiter is expected to display signatures of metal oxides and hydrides in absorption. However recent studies showed that the host star a F6 dwarf appears to be considerably more active than expected. The ability of stellar spots and faculae to mimic absorption features in a planetary atmosphere or hide them altogether is one of the most serious obstacles in exoplanet transmission studies. The high-precision photometer aboard CHEOPS is the optimal instrument to monitor the transit of WASP-17b for two main reasons. Being centred at 0.6 µm the CHEOPS photometer targets specifically the wavelengths where the stellar spectrum peaks and where optical absorbers display strong absorption features. Hence CHEOPS data is essential to solve the ongoing disputes on this planetary system regarding the activity of the host star and the presence of refractory elements in the atmosphere of the companion planet. At least 11 transits with a very high coverage (>65%) are expected to occur during AO-3 making WASP-17 b an excellent target for CHEOPS. </ul [truncated! Please see actual data for full text]