(cba:news) am cvn

Joe Patterson jop at astro.columbia.edu
Mon Mar 26 14:55:32 EDT 2018

Dear CBAers, Let's gang up on AM CVn one last time.  We're doing a 
long-term study of the Porb.  It's clear now - from the last 25 years of 
timings - that Porb is slowly decreasing.  This will surprise most AM 
CVn fans and will inspire some re-thinking of our assumptions.  But the 
rate of period change is critical, and depends most critically on the 
accuracy  of timings near the beginning and end of the interval 

We can't improve 1992.  But we can definitely gang up on 2018.  So far, 
led by Joe U, we've done OK.  But we have to keep up the pressure, and 
European coverage, especially, has been somewhat sparse.  It's a perfect 
time of year - crossing the meridian near local midnight - for long 
runs.  Long runs are especially desirable here because we have to 
distinguish the 1028 s ORBITAL from the two superhump signals (at 
1051/525 and 1011 s) which make a lot of mischief.


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