干旱区生态环境知识资源中心

Radial velocity planet search surveys of nearby solar-type stars have shown a strong scarcity of brown dwarf companions within similar to 5 AU. There is presently no comprehensive explanation for this lack of brown dwarf companions; therefore, increasing the sample of such objects is crucial to understand their formation and evolution. Based on precise radial velocities obtained using the SOPHIE spectrograph at Observatoire de Haute-Provence we characterise the orbital parameters of 15 companions to solar-type stars and constrain their true mass using astrometric data from the HIPPARCOS space mission. The nine companions not shown to be stellar in nature have minimum masses ranging from similar to 13 to 70 M-Jup, and are well distributed across the planet/brown dwarf mass regime, making them an important contribution to the known population of massive companions around solar-type stars. We characterise six companions as stellar in nature with masses ranging from a minimum mass of 76 +/- 4 M-Jup to a mass of 0.35 +/- 0.03 M-circle dot. The orbital parameters of two previously known substellar candidates are improved.