(cba:news) t pyx and v455 and, mainly

Joe Patterson jop at astro.columbia.edu
Mon Jan 12 08:12:48 EST 2015


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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