(cba:news) BT Mon, finis

Joe Patterson jop at astro.columbia.edu
Sat Dec 23 04:19:30 EST 2017

Hi CBAers,

Thanks for all the BT Mon data.  With its period so close to 8 hours, 
it's not easy to get a full light curve, and in particular to test 
securely for the presence of a secondary eclipse. (In an edge-on binary 
of LONG Porb, a secondary eclipse is expected.)

I'm not 100% persuaded yet, but a secondary eclipse seems to be absent. 
Also, the eclipses are coming very early - a full 0.05 P_orb early 
relative to the existing ephemeris.  This needs no "persuading"... and 
might signify a large period decrease. We'll repeat this next year and 
see if that trend holds up (when the drift would grow to 0.06P_orb).

But we're done for the year.  Sorry to inflict such a difficult star on 
you!  Next year it'll be easier, because we'll "know what we're looking 

joe p

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