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(cba:news) t pyx and v455 and, mainly (Joe Patterson) [2015-01-12T13:14:11Z]


Dear CBAers,

Some comments on two of our oldest friends.

It has now been 3.5 years since T Pyx's eruption, and that's enough baseline to get a good measure of its post-eruption orbital period - increased by 1 part in 10^^4. But it's not quite enough to decide whether the steady period increase IN QUIESCENCE still continues now.
That's plausible, but not yet certified (or refuted) by observation.
To test this, we mainly need a very precise measure of minimum light in the 0.07622 d wave *now*. Just one - if sufficiently precise - would now provide a sensitive test. But "sufficiently precise" means about 10-15 orbits (6-7 nights), because the weakness of T Pyx's orbital wave makes the job somewhat challenging. It's prime observing season, and observations tightly nested in time have somewhat greater value. Go for it!

In the first paper on V455 And, it was advertised as "the star that has everything". Even including some mystery periods which still haven't been successfully interpreted ("explained"). Enrique and I have done separate analyses of this year's data, and V455 seems to have one more period - a *negative superhump* at quiescence. There's still some life left in the observing season, and if we can stitch together European and USA data, we can define this phenomenon pretty well. It does require moving on this project right away, because it may be a transient phenomenon - and also because we lose 4 minutes a day.

Unlike the 67-seconf pulse tracking project - our usual interest in V455 And - this one is not sensitive to time resolution, since the candidate period is 80 minutes. With the star at mag 15.8 and the Moon out of the way, it should be a feasible target for all northern observers.

Of course, HZ Puppis and ASASSN-14mv continue to be very attractive targets! *MOre* than CP Puppis at present, since that star requires back-to-back lengthy time series.

joe
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