Context :

Aims : We present an analysis of long-term optical monitoring observations and optical spectroscopic observations of the counterpart to CXOU J205847.5+414637 ( high mass X-ray binary system ) .
We search for a variability in the light curve of Be star .

Methods : We used differential magnitudes in the time series analysis .
The variability search in the optical light curve was made by using different algorithms .
The reduction and analysis of spectra were done by using MIDAS and its suitable packages .

Results : We have performed a frequency search which gave us the value 2.404 d ^ { -1 } .
This value is attributed to the non-radial pulsation of Be star .
H \alpha emission line profiles always show double-peaked emissions with a mean equivalent width of 2.31 \pm 0.19 Å and a peak separation of 516 \pm 45 km/s .
This suggests that Be star disk is still present .
CXOU J205847.5+414637 is in X-ray quiescent state .

Conclusions :