(cba:news) CP Puppis, mostly

Joe Patterson jop at astro.columbia.edu
Mon Jan 28 19:43:43 EST 2013

Dear CBAers,

There sure a lot of great stars out there for our purposes - OT1126+08, 
SSS1222-31, and Nova Mon 2012... all rather unusual - borderline 
mysterious - stars executing nice periodic signals.  Keep up the great work!

To my delight, Berto Monard and Bob Rea have taken me up on my 
suggestion of CP Pup.  Their data shows big periodic humps near 90 
minutes - but amazingly (to me) they just don't clearly define a period. 
  I've never seen anything quite like it.  Even if you fit the data with 
the most complicated thing I can easily imagine (roughly equal 
contributions from orbit, positive superhump, and negative superhump), 
it still doesn't fit.  Accretion disk weather!

The best way out of this is to get the densest possible light curve. 
There's a lot of water in the southern heminphere, so it won't be easy. 
  But if we could get South America (Arto?  Josch?) on this star, and 
also western Australia (Greg), we could nearly track it around the 
clock.  Jan-Feb is certainly CP Pup season.  Pretty please?

I'm suggesting holding your fire re T Pyx for a couple more weeks.  We 
definitely want another salvo of data from it later in the observing 
season (about a month hence), which will nicely constrain whether the 
new (post-outburst) period is evolving or constant.

No changes in the northern menu.  For those of you doing RX0704+26 = 
V418 Gem, I strongly recommend a *short* integration time, which you 
really need to properly resolve the strong 240 s pulse.  Most observers 
think they need to go long for this star - because it's faint (~17.4), 
and because the light curve *looks* very noisy.  But it's likely that 
most of what you see as noise is actually pulse amplitude (!)  So send 
me that noisy light curve - and if you take a power spectrum, you should 
see that 240 s signal easily.  (It's listed as 480 s, but apparently the 
star has two active poles, because nearly all the power is at 240).


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