The radial velocity variability of the K giant beta Ophiuchi .2. Long-period variations

Precise relative radial velocity measurements (sigma similar to 20 m s(-1)) of the K giant beta Oph are presented and these show variations with a period of 13.05 days. Rotational modulation, low-mass companions, and radial velocity variations can be excluded as an explanation for these variations. Most likely this period results from a nonradial g-mode. A period analysis on the residual radial velocities after subtracting the contribution of the dominant period yields a long-term period of 142.3 days and a short-term period of 0.2589 +/- 0.005 days. The latter is consistent with previous works by Hatzes & Cochran. The long-term period, if real, most likely arises from rotational modulation by surface features, although the presence of a planetary companion cannot be excluded at the present time.