The HADES RV Programme with HARPS-N@TNG - occurrence rate and global detectability of the survey
Monday 2 July, 10:35
We present the complete Bayesian statistical analysis of the Harps-n red Dwarf Exoplanet Survey (HADES), which RV monitored a large sample M dwarfs with HARPS-N@TNG, over the last 6 years. The targets were selected in a narrow range of spectral types from M0 to M3, in order to study the planetary population around a well-defined class of host stars.
We study the 56 systems for which more than 10 RV data were collected, and carried out an MCMC-based analysis of all the RV time series. This allow us to derive through Bayesian statistics an accurate estimates of the detectability function of the survey. Our analysis also includes the application of Gaussian Process (GP) approach to take into account stellar activity induced RV variations around the 27 most observed targets (>70 obs). This MCMC+GP technique has proven very effective in the study of M dwarf planetary systems, helping the detection of most of the HADES planets.
From the detectability function we can calculate the occurrence rate of small mass planets around early-M dwarfs. Taking into account only the HADES planets that have already been published, the planets occurrence rate results to be only focc = 18%, for M > 2 MEarth and P < 30 d. This lower value than the usual estimates for M dwarfs, could be a hint of a lower occurrence of exoplanets around earlier-type M dwarfs .