(cba:news) TT Ari, fire away...
jop at astro.columbia.edu
Thu Nov 11 14:06:28 EST 2004
Oops, the target list is getting a little brown around the edges...
NSV 907 is all done with its outburst. Very fine 104 minute superhumps,
well documented by Arto, Tonny, Major Tom, and Mike Koppelman - and Lew
Cook and Dave Messier after the star dropped down into the grass. Now we
move on to big glass to find the orbital period. Off the CBA radar.
I haven't finished the analysis of Var79 Peg yet, but I think this star
should be kicked out too - until further notice.
It's November, and it's time we revisit TT Ari again. This star should be
plenty bright (10.7 or so) and very well placed for northerners. We were
very surprised to discover positive superhumps in the star in 1997
(Skillman et al 98 paper), and have paid some heed to the star since...
but it's time for a real campaign, with enough round-the-world coverage to
look for the fine sideband signals that the best-observed superhumpers
flash. This may enable some accurate "seismology" to be performed on the
accretion disk, although a secure theory for such things is still not
quite established. Alternatively, TT Ari may have decided to return to
its negative-superhump state... or to combine 'em.
The other bright and seasonal star is FY Per. Really kind of a mystery
star, occasionally flashing a 1.5 hour photometric period of unknown
origin. And often showing, alas, not much variability at all. John
Thorstensen's spectroscopy establishes an orbital period of 6.2 hrs.
For both of these stars you have to think about saturation. This is
especially a concern if you set up on the star in a cloudy spell, check
counts, and then it clears up. Because both stars generously rain
photons down on the Earth, you can, if you wish, be picky about which
ones you'll accept. Consider a V filter if you got one. This will
greatly reduce differential extinction and enable your data to be used
more stringently for period searches on long timescales. Clear is OK, V
BTW I'm hoping that some of our Aussie friends can contribute to TT Ari.
At +17 deg it's not so outrageous. (We have a Pacific Ocean longitude
AH Men stays the best target way Down Under.
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