What's the Frequency of M Dwarf Exoplanetary Systems?

Synthesizing Exoplanet Demographics from Radial Velocity and Microlensing Surveys, II: The Frequency of Planets Orbiting M Dwarfs

Authors:

Clanton et al

Abstract:

In contrast to radial velocity surveys, results from microlensing surveys indicate that giant planets with masses greater than the critical mass for core accretion (∼0.1 MJup) are relatively common around low-mass stars. Using the methodology developed in the first paper, we predict the sensitivity of M-dwarf radial velocity (RV) surveys to analogs of the population of planets inferred by microlensing. We find that RV surveys should detect a handful of super-Jovian (greater than MJup) planets at the longest periods being probed. These planets are indeed found by RV surveys, implying that the demographic constraints inferred from these two methods are consistent. We combine the results from both methods to estimate planet frequencies spanning wide regions of parameter space. We find that the frequency of Jupiters and super-Jupiters (1≲mpsini/MJup≲13) with periods 1≤P/days≤104 is fJ=0.029+0.013−0.015, a median factor of 4.3 (1.5−14 at 95% confidence) smaller than the inferred frequency of such planets around FGK stars of 0.11±0.02. However, we find the frequency of all giant planets with 30≲mpsini/M⊕≲104 and 1≤P/days≤104 to be fG=0.15+0.06−0.07, only a median factor of 2.2 (0.73−5.9 at 95% confidence) smaller than the inferred frequency of such planets orbiting FGK stars of 0.31±0.07. For a more conservative definition of giant planets (50≲mpsini/M⊕≲104), we find fG′=0.11±0.05, a median factor of 2.2 (0.73−6.7 at 95% confidence) smaller than that inferred for FGK stars of 0.25±0.05. Finally, we find the frequency of all planets with 1≤mpsini/M⊕≤104 and 1≤P/days≤104 to be fp=1.9±0.5.