Volume 555, July 2013
|Number of page(s)||10|
|Section||Planets and planetary systems|
|Published online||04 July 2013|
Precise radial velocities of giant stars
Landessternwarte, Zentrum für Astronomie der Universität
2 Physics Department, California Polytechnic State University, San Luis Obispo, CA 93407, USA
3 Department of Astronomy, Yale University, New Haven, CT 06511, USA
Received: 16 April 2013
Accepted: 22 May 2013
Aims. 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.
Methods. 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 were taken at Lick Observatory. Our survey includes 373 G and K giants. Radial velocity data showing periodic variations were fitted with Keplerian orbits using a χ2 minimization technique.
Results. We report the presence of two substellar companions to the K giant stars τ Gem and 91 Aqr. The brown dwarf orbiting τ Gem has an orbital period of 305.5 ± 0.1 days, a minimum mass of 20.6 MJ, 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 MJ, 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.
Key words: techniques: radial velocities / planets and satellites: detection / brown dwarfs
Based on observations collected at Lick Observatory, University of California, and at the European Southern Observatory, Chile, under program IDs 088.D-0132, 089.D-0186, and 090.D-0155.
Appendices are available in electronic form at http://www.aanda.org
© ESO, 2013
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