Precise radial velocities of giant stars V. A brown dwarf and a planet orbiting the K giant stars tau Gem and 91 Aqr

D. S. Mitchell; S. Reffert; T. Trifonov; A. Quirrenbach; D. A. Fischer

doi:10.1051/0004-6361/201321714

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arXiv · 1305.5107

Precise radial velocities of giant stars V. A brown dwarf and a planet orbiting the K giant stars tau Gem and 91 Aqr

D. S. Mitchell·S. Reffert·T. Trifonov·A. Quirrenbach·D. A. Fischer

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Abstract

We aim to detect and characterize substellar companions to K giant stars, to further our knowledge of planet formation and stellar evolution of intermediate-mass stars. For more than a decade we have used Doppler spectroscopy to acquire high precision radial velocity measurements of K giant stars. All data for this survey have been taken at Lick Observatory. Our survey includes 373 G and K giants. Radial velocity data showing periodic variations are fitted with Keplerian orbits using a chi^2 minimization technique. We report the presence of two substellar companions to the K giant stars tau Gem and 91 Aqr. The brown dwarf orbiting tau Gem has an orbital period of 305.5 +/- 0.1 days, a minimum mass of 20.6 M_Jup, and an eccentricity of 0.031 +/- 0.009. The planet orbiting 91 Aqr has an orbital period of 181.4 +/- 0.1 days, a minimum mass of 3.2 M_Jup, and an eccentricity of 0.027 +/- 0.026. Both companions have exceptionally circular orbits for their orbital distance, as compared to all previously discovered planetary companions.

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D. S. Mitchell, S. Reffert, T. Trifonov, A. Quirrenbach, D. A. Fischer. 2013-05-22. Precise radial velocities of giant stars V. A brown dwarf and a planet orbiting the K giant stars tau Gem and 91 Aqr. https://doi.org/10.1051/0004-6361%2F201321714

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