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EW Lac has shown remarkable V/R variations in 1976 - 1986, and a similar V/Rvariation has started again in around 2007, after some quasi-periodic V/Rvariation. For the first V/R variation event, we analyze the spectroscopicbehaviors of emission lines and shell absorption lines of the Balmer series.The V/R variations of the H_alpha through H_delta lines are characterized bythe different manner of variations of the individual emission lines in time lagand in duration of the V/R phases. Weak correlation is also notable between theV/R variations and other variations of the line-profile parameter such as thepeak velocities, emission line intensities and peak separations. We analyzeshell absorption lines for higher members of the Balmer series for theircentral depths and radial velocities. The optical depth of the H_alpha line isin a range of 2000 to 6000, and its long-term variation discloses differentbehaviors as compared to the V/R variations. Combining the analyses of emissionand shell absorption lines, and regarding the V/R variation as wave propagationphenomena, we find for the 1976 - 1986 event that the V/R variation is ofretrograde structure and a spiral structure is likely formed inside the disk inthe latter half of this event. The weak correlations among physical parametersare suggestive of the disk truncated at some radius. It is noticed thatremarkable stellar brightening has occurred in the latter half of the event,accompanying marked decrease of emission line intensities. As for the V/Rvariation appeared in around 2007, which looks like a recurrence of theprevious event, we found less developed state of the disk without appreciabletime lag.

Spectroscopic Variations of the Be-shell Star EW Lac in the V/R Variation Periods