Simultaneous MITSuME g ′ R c I c monitoring of S 5 0716 + 714

We present results of our intra-night optical flux monitoring observations of S5 0716+714 done simultaneously in g, RC and IC filters. The observations were done using Multicolor Imaging Telescopes for Survey and Monstrous Explosions (MITSuME) instrument on the 50 cm telescope at the Okayama Astrophysical Observatory over 30 nights between 11 March 2008 and 8 May 2008. Of these 30 nights, 22 nights have continuous (without any break) observations with duration ranging from 1 to 6 hours and hence were considered for intra-night optical variability (INOV). The remaining 8 nights have continuous observations of less than 1 hr and hence were considered only for long term optical variability (LTOV). In total we have 4888 datapoints which were simultaneous in g, RC and IC filters. Of the 22 nights considered for INOV, the object showed flux variability on 19 nights with the amplitude of variability in the IC -band ranging from ∼4% to ∼55%. The duty cycle for INOV was thus found to be 83%. A good correlation between the light curves in all the three bands was found. No time lag between different bands was noticed on most of the nights, except for 3 nights where the variation in g was found to lead that of the IC band by 0.3 to 1.5 hrs. On inter-night timescales, no lag was found between g and IC bands. On inter-night timescales as well as intra-night timescales on most of the nights, the amplitude of variability was found to increase toward shorter wavelengths. The flux variations in the different bands were not achromatic, with the blazar tending to become bluer when brighter both on inter-night and intra-night timescales; and this might be attributed to the larger amplitude variation at shorter wavelengths. A clear periodic variation of 3.3 hrs was found on 1 April 2008 and a hint for another possible periodic variability of 4 hrs was found on 31 March 2008. During our 30 days of observations over a 2 month period the source has varied with an amplitude of variability as large as ∼80%.