Comment on DM Lyr

(vsnet 742, Eric Broens)

Dear friends,

Was there any suspection that DM Lyr could be a UGSU-type CV? In Downes & Shara, DM Lyr is classified as UG-type variable without an uncertainty-sign. It is a surprise that only on the last outburst superhumps were detected, while DM Lyr has outbursts frequently (in 1994 even 4). Has this star been monitored for superhumps during the previous outbursts?

Best Regards,

comment by T. Kato

(vsnet 743)

I personally suspected DM Lyr could be an SU UMa-type dwarf nova (well, I believe every dwarf nova should be tested for a possibility of an SU UMa star -- though some may not be good ones). The suspicion first came from the discovery record by Hoffmeister, which I may have already cited somewhere.

    1928 Sept. 2   14:
               3   14
               4   13
               5   13
               6   14
               7   14
              11   14.5
              12   15
              13   16
              16  <16
This 1928 outburst is unmistakably a superoutburst from the current classfication. During one of 1994 outbursts, C. Kunjaya and I obtained some time-resolved photometry, yielding a null superhump result. We may now safely identify the 1994 outburst we observed as a normal outburst. The 1996 outburst was the first since (for us) 1994 ones we could observe.

Taichi Kato

Petterson's comment

(vsnet 745)

DM LYRAE, and respect for received wisdom

Eric Broens and Taichi Kato have made some interesting points on this star (vsnet 742, 743). Thought I would chime in.

I never really heard of this star, except as an entry on a list, until the recent eruption. I try to keep track of all CVs about which scientific papers are written, or talks given at meetings - and DM Lyr never appeared on my radar screen. Inspection of the CV Circulars shows clearly that the world of visual observers is much more inclusive. So I'm guessing that no one ever observed the star during its long eruptions, despite their high frequency.

I hope Kato's point that *all* dwarf novae should be considered superhump suspects will be fully appreciated. I strongly agree. In particular I hope people will look at stars of fairly long period, which are neglected by professional astronomers because the literature abounds with declarations that superhumps are restricted to short-period systems. If you dig deeper, you find that the support for this declaration is that it's "well-known". Referees, especially, love this phrase. It's also well-known that you can cure practically any illness by drinking the blood of gladiators.

Joe Patterson
CBA and Columbia University

Return to HomePage Wisdom is power...