Looking for TRAPPIST-1 external planets' emission in JWST archival data

Abstract

The TRAPPIST-1 system has been thoroughly observed with JWST. Unfortunately, stellar contamination issues strongly limit the interpretation of transit observations. As for emission observations, only the two closest planets have been observed through five dedicated JWST programs. We gathered all these emission observations and tried to detect the combined emission of the external planets in previous JWST MIRI observations of TRAPPIST-1; this paper presents our approach and our results. We could not achieve sufficient precision to detect the thermal emission of the outer planets and to discriminate between an all-bare rocks and an all-atmospheres scenario. However, we show that a~60 hours continuous observations at a specific phase range, when the gradient of thermal flux from the outer planets is maximum, could allow us to achieve this goal.