tokens: indicating a harder γ-ray spectrum. The curvature parameter β gives a measure of the presence of cut-off in the spectrum at high energies with a large value of β indicating a sharper cut-off. Therefore, investigation of any changes in the values of α and β parameters during the five epochs can point to changes in the γ-ray spectral shape. A change in the γ-ray spectral parameters during a flaring state could point to a change in the position of the γ-ray-emitting region. The variation of the α and β against flux during the five epochs studied here is shown in Fig. 14 . No trend on the variation of α with flux was seen during the five epochs considered here. However, a plot of β with flux (Fig. 14 ) shows a clear trend of a decrease in the curvature parameter with increasing flux. Linear least-squares fit to the data gives β = (−0.005 ± 0.009) F V + (0.168 ± 0.029) with a correlation coefficient of −0.77. Clearly the value of β is high and low at the lowest and the highest flux levels among the five epochs analysed here. Such a trend is also seen by Ackermann et al. ( 2015 ) on analysis of the FSRQs in the third catalogue of AGNs detected by Fermi (3LAC). The changes in the γ-ray spectral shape during different brightness states of 3C 454.3 could point to the emission site located at different regions during different brightness states; however, other explanations could not be ruled out. Studies on the flares of 3C 454.3 in December 2009 and November 2010 that fall in the epochs A and B studied here concluded that the γ-ray emission regions were located close to the central black hole (Jorstad et al. 2012 ; Isler et al. 2013 ). Figure 14. Variations of the parameters α and β with flux. 4.2 Connection between optical and GeV flux variations In a majority of the multiwavelength monitoring observations of blazars, close correlations between the flux variations in different bands were noticed (Bonning et al. 2009 ). This was explained on the co-spatiality of the emission regions emitting in different bands and the correlated optical and GeV flux variations can be understood in the standard leptonic emission processes according to which the same relativistic electrons produce optical and γ-ray emission via synchrotron and IC processes. However, there are a handful of blazars where the emission in the optical and GeV γ-ray bands are found not to be correlated (Chatterjee et al. 2013a ; Dutka et al. 2013 ; Cohen et al. 2014 ; MacDonald et al. 2015 ). During the 9 yr of monitoring data analysed here we found four flaring epochs in the optical, namely A,B, D, and E. During epochs A and B, the optical flare is accompanied by a γ-flare, while at the other two epochs D and E, though the optical flares have amplitudes similar to those of epochs A and B, the γ-rays during epochs D and E were either weak or undetected. This is clearly seen in Fig. 15 , where the logarithm of γ-ray flux is plotted against the logarithm of optical flux. The results of the linear
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