(cba:news) CP Puppis, rest in peace (not)

Joe Patterson jop at astro.columbia.edu
Mon Feb 13 09:26:56 EST 2017


Hi CBAers,

I've completed analysis of the CP Pup data for the season.  As was 
hinted at but not quite proved 3 years ago, the photometric period 
really is well separated - about 8% - from the spectroscopic (presumed 
orbital) period.  Hallelujah.  The instability in waveform and period 
shows that it cannot reside in the dynamical parts of the binary (the 
two stars), but must reside in the disk - the main source of light.
Your basic superhump.  Ever hear of such things?

Me too.  But 8% separation - not 2% as we thought 20 years ago, based on 
a 1-day alias - breaks all, or almost all, the rules.  It indicates a 
very strong perturbation on the disk by the secondary.  The most 
plausible way to get this is origin at the 2:1 resonance in the disk, 
not 3:1 as is customary for superhumpers.  But very few disks are *big* 
enough to reach the 2:1 resonance; only for a very extreme mass ratio 
(probably M2/M1 less than around 0.05) can the disk extend that far. 
This probably indicates a secondary less than around 0.05 Mo.

Kinda fascinating.  There are very few classical novae of short Porb, 
although the great majority of CVs are of short Porb.  This has always 
been troubling (to me; some others are strangely unruffled by it).  CP 
Pup may guide us to a solution.

But we're done for the year!

joe
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