A long-period massive planet around HD106515A

International audienceWe have performed radial velocity (RV) monitoring of the components of the binary system HD 106515 over almost 11 years using the high-resolution spectrograph SARG at Telescopio Nazionale Galileo (TNG). The primary shows long-period radial velocity variations that indicate the presence of a low-mass companion whose projected mass is in the planetary regime (msin i = 9.33 M-J). The 9.8 year orbit is quite eccentric (e = 0.57), as is typical for massive giant planets. Our results confirm the previously made preliminary announcement of the planet by Mayor et al. (2011, A&A, submitted [arXiv:1109.2497]). The secondary instead does not show significant RV variations. The two components do not differ significantly in chemical composition, as was also found for other pairs of which one component hosts giant planets. Adaptive optics images obtained with TNG/AdOpt do not reveal additional stellar companions. From the analysis of the relative astrometry of the components of the wide pair we compute an upper limit on the mass of the newly detected companion of about 0.25 M-circle dot. State-of-the-art or near-future instrumentation can provide true mass determination, thanks to the availability of the wide companion HD106515B as reference. Therefore, HD 106515Ab will allow a deeper insight into the transition region between planets and brown dwarfs