Optical bursts from 4U/MXB 1636-53

The results of observations of 15 and 26 optical bursts detected during June and July 1979 and June and July 1980, respectively, from the X-ray burst source 4U/MXB 1636-53 in a 'white light' passband are presented. The maximum burst fluxes above the persistent optical flux and integrated burst fluxes are correlated, and it appears that the maximum optical and X-ray burst fluxes are related according to a power law, consistent with optical emission from blackbody reprocessing of X-rays. The approximately linear relationship between the integrated optical and X-ray burst fluxes argues against this simple picture. The correlation of burst fluxes with waiting time since the previous burst suggests that large optical bursts come after a long waiting time. Short burst intervals observed both for optical and X-radiation suggest that not all available nuclear fuel is consumed in the thermonuclear flash which gives rise to the X-ray burst.