(cba:news) CN Ori , CP Pup, and YZ Cnc

Joe Patterson jop at astro.columbia.edu
Thu Feb 2 14:05:28 EST 2017


Hi CBAers,

CN Ori is heading back towards minimum, where its large-amplitude wave 
makes defining a period quite straightforward.  Over an increasingly 
long interval, which is our goal (as well as to test whether the wave at 
maximum is the same phenomenon).  So some long light curves right now 
would be great.  The ones at max are slightly less useful.

CP Pup.  Be still, my beating heart.  I've lusted after this star for a 
few years.  Its large-amplitude photometric wave occurs at a period a 
few percent longer than Porb.  in our 1995 paper (me and Warner 1995) we 
said "probably 2%", which would be basically a normal superhump, nothing 
particularly special.  But 2-3 years ago, our campaign data strongly 
preferred a number near 7%.  The difference may seem small, but it's 
"astronomically" significant - it would be quite inconsistent with the 
usual "3:1 resonance" explanation for superhumps.

The signal is of large amplitude but *poor* coherence - so much so that 
it's hard to unambiguously count cycles from night to night.  We 
absolutely need 2-longitude coverage, and really a 3rd is needed to be 
sure (and in fact a *streak* of a few consecutive nights of 3-longitude 
coverage).  For you southerners down there, consider making this star a 
high-priority target.  2 versus 7... it's one or the other (they differ 
by 1 cycle/day over one day's span), and quite a bit rides on the answer.

It's about mag 15.5, nothing too challenging.

YZ Cnc.  Getting close to the "expected" rise to a normal max, so now's 
the time to watch carefully... and compare to the energing AAVSO 
lightcurve to evaluate whether what you see is a steady rise, or just 
some more eeratic variability.  Notify if it looks interesting!

That's three of our targets.  More later.

joe

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