'Retired' Planet Hosts: Not So Massive, Maybe Just Portly After Lunch (Speaker: James Lloyd)

Date: 
Tuesday, September 24,
4:00pm to 5:00pm
Speaker(s): 
James Lloyd, Cornell University

Abstract:
Studies of the planet abundance as a function of stellar mass have shown a strong increase in the frequency of radial velocity planet detection around stars more massive than 1.5 times the mass of the sun, and that such stars are deficit in short period planets. These planet searches have relied on subgiant stars for a sample of high mass stars, which are hostile to precision Doppler measurements while on the main sequence due to rotation and activity. However, there is now controversy as to the whether these subgiants are indeed evolved from a population of high mass stars. The erroneous mass determinations most likely arise from uncertainties in the extrapolation of solar-calibrated mixing length theory to the red giant branch, the treatment of convective overshoot, or the use of the Eddington gray boundary condition approximation for convective atmospheres. The deficit of short period planets can be explained by tidal capture. The planet abundance increase requires either a high rate of false positives in giant stars due to signals of stellar origin or a new mechanism to migrate planets inwards during the early post main sequence evolution of the host star.