  We report the detection of 3 new extrasolar planets from the precise Doppler
survey of G and K giants at Okayama Astrophysical Observatory. The host stars,
namely, 18 Del (G6 III), xi Aql (K0 III) and HD 81688 (K0 III-IV), are located
at the clump region on the HR diagram with estimated masses of 2.1-2.3 M_solar.
18 Del b has a minimum mass of 10.3 M_Jup and resides in a nearly circular
orbit with period of 993 days, which is the longest one ever discovered around
evolved stars. xi Aql b and HD 81688 b have minimum masses of 2.8 and 2.7
M_Jup, and reside in nearly circular orbits with periods of 137 and 184 days,
respectively, which are the shortest ones among planets around evolved stars.
All of the substellar companions ever discovered around possible
intermediate-mass (1.7-3.9 M_solar) clump giants have semimajor axes larger
than 0.68 AU, suggesting the lack of short-period planets. Our numerical
calculations suggest that Jupiter-mass planets within about 0.5 AU (even up to
1 AU depending on the metallicity and adopted models) around 2-3 M_solar stars
could be engulfed by the central stars at the tip of RGB due to tidal torque
from the central stars. Assuming that most of the clump giants are post-RGB
stars, we can not distinguish whether the lack of short-period planets is
primordial or due to engulfment by central stars. Deriving reliable mass and
evolutionary status for evolved stars is highly required for further
investigation of formation and evolution of planetary systems around
intermediate-mass stars.
