Combining the Euclid and Roman space missions to measure the mass of cold terrestrial planets

The study of exoplanets beyond the snow line is essential to understand planetary formation mechanisms. In this context, gravitational microlensing is a particularly effective indirect detection method to identify cold and faint planets located at distances of approximately 1 to 10 AU from their host star. This work is part of the Nancy Grace Roman space mission, dedicated to the detection of exoplanets via gravitational microlensing. It aims to improve the mass measurement of terrestrial exoplanets detected through this method. The adopted approach combines the modeling of microlensing photometric light curves with the analysis of high-angular-resolution images obtained several years before or after the event peak. The lens mass–distance relations derived from these two analyses allow us to tightly constrain its physical parameters, such as the planetary mass. This approach, which can also be applied to Euclid observations and future Roman surveys, will contribute to a better demographic characterization of cold exoplanets in the Milky Way.