23 Dec 2011: Tha semi-majors axis is derived from the stellar radius and the ratio a/Rs given by Fressin et al. 2011. The semi-major axis derived the the stellar mass and the orbital period is 0.138 ± 0.002 AU.
The mass limit is derived from RV measurements. "Theoretical considerations give 0.66 MEarth < MP < 3.04 MEarth" (Fressin et al. 2011)
Gaia Search for (sub)stellar Companions of Exoplanet Hosts
MICHEL K.-U. & MUGRAUER M.
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The Kepler Giant Planet Search. I. A Decade of Kepler Planet-host Radial Velocities from W. M. Keck Observatory
WEISS L., ISAACSON H., MARCY G., HOWARD A., FULTON B., et al.
ApJ Suppl.
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, 8
paperarxiv
Cold Jupiters and improved masses in 38 Kepler and K2 small-planet systems from 3661 high-precision HARPS-N radial velocities. No excess of cold Jupiters in small-planet systems
BONOMO A., DUMUSQUE X., MASSA A., MORTIER A., BONGIOLATTI R. et al.
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, 677
, A33
paperarxiv
Orbital obliquity sampling in the Kepler-20 system using the 3D animation software Blender