AZ Cas periastron Ca HK region

[Robin Leadbeater]

It is 7 months since I last looked at AZ Cas and it is now approaching periastron ( ~end Novemeber) The spectrum in the Ca HK region has changed significantly since the last spectrum taken just after the end of the eclipse. The sharp chromospheric lines produced by the B star shining through the extended cool supergiant atmosphere, seem to have gone (particularly noticeable at Ca II K) and the spectrum looks much like a B0i star, with some ripples superimposed from the M star spectrum.

Cheers
Robin