(cba:news) TT Ari in its darkest lair
jop at astro.columbia.edu
Tue Nov 10 13:24:45 EST 2009
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
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
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