Detection of an exoplanet around the evolved K giant HD 66141

¹ Korea Astronomy and Space Science Institute, 776, Daedeokdae-Ro, Youseong-Gu, 305-348 Daejeon, Korea
e-mail: bclee@kasi.re.kr; iwhan@kasi.re.kr; kmkim@kasi.re.kr
² National Astronomical Research Institute of Thailand, 50200 Chiang Mai, Thailand
³ Crimean Astrophysical Observatory, Nauchny, 98409 Crimea, Ukraine
e-mail: davidmkrt@gmail.com
⁴ Department of Astronomy and Atmospheric Sciences, Kyungpook National University, 702-701 Daegu, Korea
e-mail: mgp@knu.ac.kr

Received: 5 September 2011
Accepted: 6 November 2012

Abstract

Aims. We have been carrying out a precise radial velocity (RV) survey for K giants to search for and study the origin of the low-amplitude and long-periodic RV variations.

Methods. We present high-resolution RV measurements of the K2 giant HD 66141 from December 2003 to January 2011 using the fiber-fed Bohyunsan Observatory Echelle Spectrograph (BOES) at the Bohyunsan Optical Astronomy Observatory (BOAO).

Results. We find that the RV measurements for HD 66141 exhibit a periodic variation of 480.5  ±  0.5 days with a semi-amplitude of 146.2  ±  2.7 m s^-1. The Hipparcos photometry and bisector velocity span (BVS) do not show any obvious correlations with RV variations. We find indeed 706.4  ±  35.0 day variations in equivalent width (EW) measurements of H_α line and 703.0  ±  39.4 day variations in a space-born measurements 1.25μ flux of HD 66141 measured during the COBE/DIRBE experiment. We reveal that a mean value of long-period variations is about 705  ±  53 days, whose origin is a rotation period of the star and variability that is caused by surface inhomogeneities. For the 480-day periods of RV variations an orbital motion is the most likely explanation. Assuming a stellar mass of 1.1  ±  0.1 M_⊙ for HD 66141, we obtain a minimum mass for the planetary companion of 6.0  ±  0.3 M_Jup with an orbital semi-major axis of 1.2  ±  0.1 AU and an eccentricity of 0.07  ±  0.03.