Long-term and periodic variability of 4U 1258-61 (GX304-1)

We present optical spectroscopy and photometry of the Be/neutron star binary system 4U 1258–61 obtained over the period 1977–83. We find evidence for the evolution of a circumstellar envelope through the course of the observations with a decline in optical activity resulting in a state with no visible Hα emission. This may be related to a recent cessation of X-ray emission from the source. X-ray observations made with the Ariel V and Copernicus satellites between 1975 and 1979 are also presented. An X-ray flare seen with Ariel V is consistent with the proposed 133 day period for this system. The ratio of the strengths of the blue and red components of the double-peaked Hα emission line shows considerable variability and may be modulated at the X-ray flare period. We discuss models which may explain some of the observed properties of 4U 1258–61.