3 Results

On 13 out of the total 21 nights, the DLCs span a minimum duration of 4 hours and have a fairly dense coverage (about 4 data points per hour in each passband). Of the 5 nights observed from VBO, three (March 16, 17 and 18) overlap with the monitoring carried out from UPSO. Fortunately, the two cloudy nights at UPSO (March 17 and 18) happened to fall within this overlap and this deficit can thus be partly offset with the available VBO data. The March 16 data from both observatories have high signal/noise ratio and are found to be in good agreement (Figs. 1 and 2). Note that all 4 passbands have been used on 15 of the nights, whereas only R and I data are available for the two nights covered from VBO alone. Also, on 4 nights at UPSO only 3 filters (V, R , I) were used.

In order to examine inter-night and long-term optical variability trends more clearly, we have generated a compressed version of the DLCs, integrating just the data acquired during the first and the last hour of observations on each night. This gave two data points per night (excepting a couple of cases when the entire duration of observation was less than two hours and therefore only one data point could be obtained). The above integration typically involved 3-4 data points in B and V, and 5-6 data points in R and I passbands. The compressed DLCs are shown in Fig. 3.

  

Figure 3: Compressed DLCs generated from the profiles shown in Figs. 1 and 2. These DLCs represent only the data acquired during the first and the last hour of the individual nights. In order to enhance clarity, we have applied fixed offsets of 0.45, 0.0, -0.2 and -0.35 magnitudes, respectively, to the B, V, R and I-band DLCs of the blazar. The corresponding offsets for the DLCs of the comparison stars are 0.1, 0.0, -0.1 and -0.25 magnitudes, respectively. Note that the gap in the R and I data of UPSO on March 19 and 20 has been filled using the VBO observations, since one of the comparisons star 1 was common to the two datasets