Abstract:
We report multi-colour optical monitoring of
the intra-day variable blazar S5 0716+71 with a dense
temporal coverage over a total duration of 4 weeks in
February/March 1994. Four filters (BV Johnson and RI
Cousins) were used on a majority of the nights. The light
curves of the blazar were derived relative to two compar
ison stars present on the CCD frames. Intensity varia
tions of ≥ 0.05 mag from night-to-night were observed in
half the cases and a good correlation between the light
curves in the different passbands was noticed (as also for
the observed intra-night variations). There seems to be
no correlation between flux and optical spectral index of
the blazar. In all, three prominent events of intra-night
variability were detected, each with a rate of ≥ 0.1 mag
per hour, lasting for at least 3 hours. Each of these flaring
segments of the blazar light curves can be well fitted with
an exponential intensity profile whose rate of variation is
essentially the same for all the passbands. No clear event
of ultra-rapid fluctuations of the blazar on time scale ≤ 1
hour was detected in these multi-colour data. Present ob
servations have been carried out during a low brightness
level of the blazar and they have no large amplitude variable events.
