We present here the detection of a brown dwarf orbiting the A9V star HD 180777 .
The radial velocity measurements , obtained with the ELODIE echelle spectrograph at the Haute-Provence Observatory , show a main variation with a period of 28.4 days .
Assuming a primary mass of 1.7 M _ { \odot } , the best Keplerian fit to the data leads to a minimum mass of 25 M _ { Jup } for the companion ( the true mass could be significantly higher ) .
We also show that , after substraction of the Keplerian solution from the radial velocity measurements , the residual radial velocities are related to phenomena intrinsic to the star , namely pulsations with typical periods of \gamma Dor stars .
These results show that in some cases , it is possible to disentangle radial velocity variations due to a low mass companion from variations intrinsic to the observed star .