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S. Frink, D.S. Mitchell, A. Quirrenbach (UC San Diego), D.A. Fischer, G.W. Marcy (UC Berkeley)
We report precise radial velocity measurements of the K giant iota Dra, which suggest that a substellar companion is orbiting the primary star in a rather eccentric orbit. High resolution spectra have been collected at Lick Observatory using the Iodine Cell technique over the past 18 months, achieving a radial velocity precision of about 5 m/s in a single measurement. The semi-amplitude of the observed radial velocity variations is about 300 m/s, and the shape of the curve is consistent with Keplerian variations caused by a substellar companion that could either be a giant planet or a Brown Dwarf.
We consider it very unlikely for the particular case of iota Dra that the observed radial velocity variations are caused by non-radial pulsations or rotational modulation of surface features, though this might be the case for the radial velocity variations observed for most other K giants in our sample. Located at a distance of only 31 pc, we use the non-detection of the substellar companion by Hipparcos to derive an upper limit for the companion mass. The substellar companion to iota Dra seems to be first one found to orbit a giant rather than a solar-type star.
The author(s) of this abstract have provided an email address for comments about the abstract: sabine@ucsd.edu