Connections between X-ray and optical variability in the low mass X-ray binary 1735-444

We present the results of a long duration (4 day) simultaneous optical and X-ray observation of the low mass X-ray binary 1735 - 444. The observed X-ray and optical fluxes are correlated; the strength of this correlation is increased when allowance is made for the relatively large orbital modulation of the optical light. A simple interpretation of the optical radiation as reprocessed X-ray in a blackbody disc leads to an implausibly low disc temperature if the disc is assumed to have constant geometry. (author)