(cba:news) CN Ori , CP Pup, and YZ Cnc
jop at astro.columbia.edu
Thu Feb 2 14:05:28 EST 2017
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.
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