Why does not SS Cyg show a double peaked Ha-line - or does it...?

Affiliation
Svensk Amator Astronomisk Forening, variabelsektionen (Sweden) (SAAF)
Sat, 07/13/2024 - 12:10

Hi all!

I have a possibly somewhat narrow question. I'm interested in not just doing photometry on CVs, but also spectroscopy. I came upon the idea of exploring the characteristic double peaks of emission lines in CVs in quiescence, caused by the ackretion disc being limited in diameter (following Horne & Marsh, 1986, as also decribed in Warner's (1995) and Hellier's (2001) books. 

Doing spectroscopy on CVs in quiescence is challenging as they are faint - so I started out with SS Cyg. High in the sky and relatively bright. However, I find no double peaked emission lines, not in my spectra and not in any high-resolution spectra I find captured by others. So my puzzle: is there no double peaks in SS Cyg? If now, how can we understand that - if they are caused by the ackretion disk, surely they would appear there as well...?

Any ideas on this is warmly welcome. I feel a bit confused. 

Magnus