Based on observations made with the HARPS instrument on ESO's 3.6 m telescope at the La Silla Observatory in the frame of the HARPS GTO programme ID $\langle$ 072.C-0488 $\rangle$ and under programme ID $\langle$ 073.D-0578 $\rangle$ .

.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.

Tables 3 and 4 are only available in electronic form at http://www.aanda.org

.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.

... possible

The stellar characteristics of $\mu$ Arae are not described here, since it is not within the scope of this paper to discuss the host star. We refer instead to already published data in Butler et al. (2001) and Santos et al. (2004).

.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.