(cba:news) AA Dor and T Pyx

Joe Patterson jop at astro.columbia.edu
Sun Dec 10 07:04:16 EST 2017

Hi CBAers,

I'm getting close to finishing the IM Nor paper.  Only a few CBAers 
contributed to this one (Gordon, Berto, and Paul Warhurst so far); it's 
very faint, far southern, and obscure - discouragements to most of us.

This paper will go into some detail concerning the irradiation of the 
donor star by the hot white dwarf, in the aftermath of a nova explosion. 
I would like to include light curves from a classic supersoft binary and 
a classic hot-subdwarf binary - stars in which heating effects are truly 
obvious and well-known. It's hard to convince people of the importance 
of heating in CVs; some think it's obvious, and others think it's 
impossible.  And I think there's a third group ("maybe true but of no 

AA Dor is a very famous star with a beautiful light curve - primary 
eclipse, secondary eclipse, and sinusoidal wave obviously signifying the 
heating of the brown-dwarf secondary by the hot-subdwarf primary.  It 
has been analyzed in great detail - it competes with HW Vir as the 
prototype of the class (sort of like SS Cyg and U Gem battling for the 
honors among dwarf novae).

CBA light curves of AA Dor would be a nice addition to our paper. We 
already have a beautiful orbital light curve of a supersoft (QR And), 
and AA Dor would bookend it nicely.  It would be a nice primer on 
heating effects - in a detached binary (AA Dor) and a full 
accretion-disk system (QR And).  At magnitude 11.5, AA Dor is blindingly 
bright; I recommend a V filter if you have one you like - although 
unfiltered is OK too if you scrupulously avoid large airmass.  As befits 
a simple star, 6 hours is both the binary period and the right 
ascension.  Nice holiday gift.

      Ali is the greatest,
      But now hear the latest:
      AA Dor
      Is what we wish for.

The holidays have also brought T Pyx back in the sky.  Let's get going 
on this star.  Southern USA observers can contribute, as well as - 
obviously - the australites.  Each new season brings peril to our 
favorite theory: death by heating.

joe p

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