SIMBAD references

We report optical CCD observations of the microquasar LS 5039. Its photometric behaviour is studied over different orbital periods with a time separation of three years. We do not detect evidences of an ellipsoidal modulation above the ±0.01mag level, thus confirming the previous results reported by Clark et al. (2001A&A...376..476C). The light curve of LS 5039 has also been explored with a time resolution of 30s but the source also appears to be stable on such shorter time scales. Possible scenarios consistent with the non-detection of optical variability are considered.