It's a small world: On the nature of the planets around the coolest Kepler stars
by
Eric Gaidos(University of Hawaii)
→
Europe/Stockholm
FA 32
FA 32
Description
Kepler mission findings have unequivocally demonstrated that small planets are common around stars, and indicate that planets may be even more common around K and M dwarf stars than around solar-type stars. However, besides radii, the properties of these planets are not known. Doppler radial velocity studies to measure masses are challenged by the faintness of Kepler stars and limited observational resources. We constrain the densities of Earth- to Neptune-size planets around very cool Kepler stars by comparing Keck/HIRES radial velocity
measurements of 150 nearby stars to a model based on Kepler candidate planet
radii and a power-law mass-radius relation. Our analysis is based on the presumption that the planet populations around the two sets of stars are the same. The model can reproduce the observed distribution of radial velocity variation over a range of parameter values, but, for the expected level of Doppler systematic error, the consistentcy between Kepler and Doppler data demands that these planets are primarily made of rock and metal, having a power-law mass-radius relation with index ~4. Our comparison also suggests that Kepler’s
detection efficiency relative to ideal calculations is less than unity. One possible
source of incompleteness is target stars that are misclassified subgiants or giants,
for which the transits of small planets would be impossible to detect.
