(Proposal ID) S15B-022

(PI) Ryu, Tsuguru

(Proposal Title)
Direct imaging for intermediate mass giants with RV trends

(Abstract)
At Okayama Astrophysical Observatory (OAO), radial velocity(RV) survey 
targeting intermediate mass giants(1.5-5M_sun) is done over a decade. Through 
the survey, linear RV trends are observed some targets. RV trends indicate the 
presence of a distant object. However, causal objects for the RV trends are not
 only planets or brown dwarfs but also stars. Direct imaging instruments can 
easily detect a stellar mass companion, so we can confirm whether the distant 
stellar companion which can make observed long-term RV trend exists by using 
direct imaging instrument. Even if stellar companions are not detected, the 
range of causal mass and the semi-major axis is limited from direct imaging 
observation result, minimum causal mass for RV trend and linear RV trend. 
We would like to identify the causal objects for RV trends by using HiCIAO 
or IRCS instrument.