PLANETS AROUND EVOLVED STARS

摘要

More than one hundred extra-solar planets around solar-like stars have been discovered in the past decade. However, until now there are only few candidates of sub-stellar companions (brown dwarf or planet) discovered around evolved stars. Due to the intrinsic stellar variability the detection of low-mass companion around evolved stars is very difficult. Here I describe two of five sub-stellar companions to giant/subgiant stars known so far. Evidence for giant planetary companions to luminous K giants HD 47536 and HD 122430 has been found by using the radial velocity technique. The simultaneous calibration and cross-correlation method have been applied to monitor the variations in the stellar radial velocity. The detection of low-mass extra-solar planets using this method is very difficult and might be successfully applied only to subgiants, which are much less variable than luminous giants.