1070

Annelies Mortier

Improving the bulk densities for small planets observed with HARPS-N, K2, and CHEOPS

Transiting planets offer a unique opportunity to measure the bulk density of an exoplanet. This enables studies of planet interior composition and in turn informs planet formation and evolution so we can get a better understanding of the large diversity of exoplanets in the Universe. Despite thousands of known exoplanets, there is still a lack of well characterised small planets. The HARPS-N Science Team has been leading the effort of characterising these small transiting planets, representing a third of these well-characterised small planets, offering precise and accurate masses across parameter space, including some of the longest-period small planets with precise masses. We have secured additional data of CHEOPS for several of our prime targets. This has allowed us to improve both the radii and masses of these planets. The precise transit photometry of CHEOPS delivers an improved radius. Furthermore, having two new transits with CHEOPS has reduced the uncertainties on the period and transit time allowing narrower priors on the RV model and thus enabling a more precise mass measurement. In this talk, I will present the first results of our observing programme combining precise CHEOPS and HARPS-N data with archival K2 photometry delivering the best possible bulk density measurement for these small planets.