S. Gettel (Penn State), G. Nowak, P. Zielinski, M. Adamów, A. Niedzielski (Torun Centre for Astronomy), A. Wolszczan (Penn State), G. Maciejewski (Torun Centre for Astronomy)
We present discoveries of planet-mass companions to two K-giant stars, HD 240237, and BD+20 274, by the ongoing Penn State - Torun Planet Search (PTPS) conducted with the 9.2-m Hobby-Eberly Telescope (HET) and the High Resolution Spectrometer (HRS; R=60,000). For the estimated stellar masses of 0.85 M☉ for HD 240237 and 1.8 M☉ for BD+20 274, the corresponding minimum planet masses are 5.3 MJ and 5.5 MJ, respectively. The Keplerian orbits derived from model fits to the radial velocity data are characterized by the respective semi-major axes of 2 AU and 1.5 AU, eccentricities of 0.37 and 0.27, and orbital periods of 740 days and 720 days. Our analysis of the growing population of substellar –mass bodies orbiting giant stars strengthens the existing evidence for a stellar mass – planet mass correlation, a weak or non-existent correlation between stellar metallicity and planet frequency, and the existence of a lower limit to the orbital radius, which is currently constrained by the observations to be ≤0.6 AU.
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