A Massive Planet to the Young Disc Star HD 81040

Abstract

We report the discovery of a massive planetary companion orbiting the young disc star HD 81040. Based on five years of precise radial-velocity measurements with the HIRES and ELODIE spectrographs, we derive a spectroscopic orbit with a period $P =1001.0$ days and eccentricity $e = 0.53$. The inferred minimum mass for the companion of $m_2\sin i = 6.86$ M$_\mathrm{Jup}$ places it in the high-mass tail of the extrasolar planet mass distribution. The radial-velocity residuals exhibit a scatter significantly larger than the typical internal measurement precision of the instruments. Based on an analysis of the Ca II H and K line cores, this is interpreted as an activity-induced phenomenon. However, we find no evidence for the period and magnitude of the radial-velocity variations to be caused by stellar surface activity. The observed orbital motion of HD 81040 is thus best explained with the presence of a massive giant planet companion.

9 pages, 5 figures, 4 tables. Accepted for publication in A&A