The double phase curve of TRAPPIST-1b and c at 15 microns

Small rocky planets are now known to be very frequent in temperate orbits around low-mass M-dwarfs. The most pressing question regarding these ubiquitous planets concerns their capacity to maintain significant secondary atmospheres despite the adverse environment (high XUV fluxes, winds) and history (long pre-main-sequence) brought by their small host stars. Here, we present the photometric observation by JWST/MIRI of the combined thermal phase curve of the two inner planets of the TRAPPIST-1 system (Cycle 2 program 3077). These observations aimed to determine if the two planets are bare rocks or not by complementing the Cycle 1 measurements of their daysides' thermal emission at 15 microns (for b and c) and 12.8 microns (for b).