An R~500 spectrum of this object taken near maximum light using an ALPY 600 spectrograph. A significantly reddened F5v star. If this is as predicted a gravitational microlensing event, the spectrum should not change as the brightness returns to normal.
Blue - measured spectrum
Red - F5v Pickles reference spectrum
Green - measured/reference (smoothed)
Interestingly I also recorded an early spectrum of the similar event in 2006 (Var 06 Cas) using a Star Analyser, confirming from the spectrum that it was not a typical variable.
http://www.threehillsobservatory.co.uk/astro/spectra_30.htm
Cheers
Robin