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(cba:news) TT Ari in its darkest lair (Joe Patterson) [2009-11-10T18:24:46Z]


Dear CBAers,

Some amazing light curves of the quiescent TT Ari coming from the western USA observers, plus Mike Potter in Maryland who has managed to extend the coverage by 2-3 hours to the east. I'm still hoping for good things from Europe, but I fear that weather there has turned bad - except for Enrique Agustino (Spain) who has been waging a heroic struggle with a 4-inch telescope (I think!). Just a little, so far, from NZ and AU, but hope springs eternal there too.

I've never seen anything like these light curves. In fact, no one has - not for TT Ari, and not for any other CV. About 7 out of every 11 hours, the star is down at V=16.3, and shows the ORBITAL period - for the first time ever. There is then no activity, just a "heating" light curve which is likely the result of the hot WD illuminating the secondary's face. Then the star goes into convulsions at V~15 for 4 hours, then rests again... to repeat the cycle about every 11 hours. Just flat astounding.

So far, we've learned more from the V (or, if you can't spare the photons, clear) light curves than from the multicolor photometry. But that's probably because it has been at true quiescence for only 1 week. Fortuitously I'm about to leave on an observing run with the 2.4 m telescope; if weather permits, I'll spin filters and likely deconvolve this star into M dwarf and hot WD. The flickering itself, when it's there, is broadband and not too likely to cough up much information from multiband observations. I slightly recommend choosing one filter and sticking with it. Also, there's value in preserving your setup as much as feasible; I've had enough simultaneous coverage to calibrate the various observers.

I say "slightly recommend" because this is in the absence of real knowledge about what we are observing. A year from now, I'll have a more definite opinion about how we *should* have observed it!

More info about other stars tomorrow. Is there help on the way from other longitudes re TT Ari? It would be great - the coherence of this 11 hour cycle is far from established, and it's a damn tough periodicity to evaluate!

joe