  We have obtained optical spectroscopy and photometry data during four years
after the event. The long-term photometric light-curve and the equivalent
widths of the Halpha and He I 6678 lines were used to monitor the state of the
Be star disk. The Halpha line profiles show evidence for V/R variability that
was accounted for by fitting the Halpha spectral line profile with two Gaussian
functions. We divided our data into three phases according to the intensity of
the X-ray, optical, and infrared emission. Phase I covers the rise and decay of
the giant X-ray outburst that took place in October to November 2017. We
interpret phase II as the dissipation of the Be star equatorial disk and phase
III as its recovery. The timescale of a complete formation and dissipation
process is about 1250 days. The epoch when the dissipation process stopped and
the reformation period began is estimated to be around MJD 58530. We find a
delay of about 100 to 200 days between the minimum of the optical or infrared
intensity and the strength of the Halpha line after the X-ray outburst, which
may indicate that the dissipation of the disk begins from the inner parts. The
motion of the density perturbation inside the disk is prograde, with a V/R
quasi-period of about four years. The source shows a positive correlation in
the (B-V) color index versus V-band magnitude diagram, which implies that the
system is seen at a small or moderate inclination angle.
