5 Conclusions

The dense temporal B, V, R and I CCD monitoring of the variable blazar S5 0716+71 is presented over a total duration of about 4-weeks. These observations along with the optical monitoring carried out by Wagner et al. (1996) and by Ghisellini et al. (1997) have been used to derive the following useful results:

1.

The present light curves in all four passbands show tight correlation. This indicates that the optical spectrum of the flaring component is similar to that of the base emission. It appears that the blazar outbursts are superposed on a constant base level emission.

2.

The optical spectral index of the blazar varies between 0.81 to 1.01 with a mean value of 0.84 and has no dependence on the flux.

3.

No clear event of ultra-rapid fluctuations of the blazar on time scale $\le$ 1 hour was detected during the present campaign.

4.

Events with large amplitude ($\ge$ 1 mag) brightening or fading have almost the same duration of about 30 days. Present observations have been carried out when the source was in a low optical state.

5.

The prominent events of intra-night variability are well fitted with an exponential intensity profile with essentially the same rate of variations in all the optical passbands.

Acknowledgements

We gratefully acknowledge the useful discussions with P.J. Wiita. Thanks are also due to anonymous referee for useful comments.