Nela Dvořáková 19.7.2019 1 Abstract We study a representative of a diverse group of stars exhibiting the B[e] phe- nomenon, designated MWC 939. This object might be an important link be- tween the stage of the asymptotic giant branch and planetary nebula stage as it is one of a few such objects observed. Our focus is aimed at spectral analysis of the circumstellar matter around the central star. We assemble a line list for MWC 939 and observe variations of its spectrum. Electron density and temper- ature are estimated using nebular diagnostics of ratios of [S II] λλ 6716, 6731 ˚A and [O I] λλ 6300, 6364 ˚A and 5577 ˚A. These estimates are then used for detailed calculations of the structure of circumstellar envelope. 1