HADES RV Programme with HARPSN at TNG. XV. Planetary occurrence rates around earlyM dwarfs
Abstract
Aims: We present the complete Bayesian statistical analysis of the HArpsn red Dwarf Exoplanet Survey (HADES), which monitored the radial velocities of a large sample of M dwarfs with HARPSN at TNG over the last 6 yr.
Methods: The targets were selected in a narrow range of spectral types from M0 to M3, 0.3 M_{⊙} < M_{★} < 0.71 M_{⊙}, in order to study the planetary population around a welldefined class of host stars. We take advantage of Bayesian statistics to derive an accurate estimate of the detectability function of the survey. Our analysis also includes the application of a Gaussian Process approach to take into account stellaractivityinduced radial velocity variations and improve the detection limits around the mostobserved and mostactive targets. The Markov chain Monte Carlo and Gaussian process technique we apply in this analysis has proven very effective in the study of Mdwarf planetary systems, helping the detection of most of the HADES planets.
Results: From the detectability function we can calculate the occurrence rate of smallmass planets around earlyM dwarfs, either taking into account only the 11 already published HADES planets or adding the five new planetary candidates discovered in this analysis, and compare them with the previous estimates of planet occurrence around Mdwarf or solartype stars: considering only the confirmed planets, we find the highest frequency for lowmass planets (1 M_{⊕} < m_{p} sin i < 10 M_{⊕}) with periods 10 d < P < 100 d, {f_{{{occ}}}} = 0.85_{  0.21}^{ + 0.46}, while for shortperiod planets (1 d < P < 10 d) we find a frequency of {f_{{{occ}}}} = 0.10_{  0.03}^{ + 0.10}, significantly lower than for laterM dwarfs; if instead we also take into account the new candidates, we observe the same general behaviours, but with consistently higher frequencies of lowmass planets. We also present new estimates of the occurrence rates of longperiod giant planets and temperate planets inside the habitable zone of earlyM dwarfs: in particular we find that the frequency of habitable planets could be as low as η_{⊕} < 0.23. These results, and their comparison with other surveys focused on different stellar types, confirm the central role that stellar mass plays in the formation and evolution of planetary systems.
All RV and activity data are only available at the CDS via anonymous ftp to cdsarc.ustrasbg.fr (ftp://130.79.128.5) or via http://cdsarc.ustrasbg.fr/vizbin/cat/J/A+A/664/A65
 Publication:

Astronomy and Astrophysics
 Pub Date:
 August 2022
 DOI:
 10.1051/00046361/202142828
 arXiv:
 arXiv:2203.04648
 Bibcode:
 2022A&A...664A..65P
 Keywords:

 techniques: radial velocities;
 stars: lowmass;
 stars: activity;
 methods: statistical;
 planets and satellites: detection;
 Astrophysics  Earth and Planetary Astrophysics;
 Astrophysics  Instrumentation and Methods for Astrophysics;
 Astrophysics  Solar and Stellar Astrophysics
 EPrint:
 21 pages, 14 figures, 8 table. Accepted by A&