The periodic spectroscopic variability of FU Orionis
FU Orionis systems are young stars undergoing outbursts of disc accretion and where the optical spectrum contains lines associated with both the di sc photosphere and a wind component. Previous observations of the prototype FU Orionis have suggested that the wind lines and the photospheric lines are modulated with periods of 14.54 and 3.54 days respectively (Herbig et al. 2003). We have re-observed the system at higher spectral resolution, by monitoring variations of optical line profiles over 21 nights in 2007 and have found periods of 13.48 and 3.6 days in the wind and disc components, consistent with the above: this implies variability mechanisms that are stable over at least a decad e. In addition we have found: i) that the variations in the photospheric absorption lines ar e confined to the blue wing of the line (centred on velocity � 9 km s 1 ): we tentatively ascribe this to an orbiting hotspot in the disc which is obscured by a disc warp during its recedin g phase. ii) The wind period