gamma-ray signal from the source is estimated after applying energy dependent selection cuts to the signal. Residual background of the observation is measured around a control region [@2017MNRAS.468.1534A]. The distribution of the events is shown in Figure \[theta2\]. In total, there was an excess of ($365.8\pm 69.1$) events in the signal region $\theta^2 < 0.02\,\deg^2$, where $\theta^2$ is the squared angular distance between the reconstructed source position of the events and the nominal position of the expected source. The data taken during MJD 57228 (2015 July 25) contribute $\geq 61\%$ of excess events of the whole sample of data. The source was detected at a significance level of $7.24\,\sigma$ during MJD 57228 (Fig. \[theta2\]).

The LC of the VHE gamma-ray integral flux above 100GeV ($F_{>100\,\text{GeV}}$) is shown in Figure \[fig\_lc\] with the details presented in Table \[tab\_tev\_flux\]. The constant flux hypothesis is disfavoured with $\chi^2/\text{d.o.f.} = 14.5/4$ ($P_{value}=0.005$). The peak flux, detected on MJD 57228 (hereafter flare night), is twice the average flux over the whole period of observation, $F_{>100\,\text{GeV, ave}}=~(4.7 \pm 1.2) \times 10^{-11}$phcm$^{-2}$s$^{-1}$. Real correlation analysis for such a short period around the flare night is beyond the reach with the available data sample shown in Figure \[fig\_lc\]. 