(cba:news) T Pyx 2020-1
jop at astro.columbia.edu
Sat Dec 5 08:50:54 EST 2020
As many of you know, we have a paper on IM Nor/T Pyx about to go out the
door (early version on astro-ph a few weeks ago). Although IM Nor is
nominally the subject, the crux of the relevant physics lies with T Pyx,
because that star's historical record is vast... and also because the
analysis of IM Nor itself is greatly hampered by interstellar extinction.
So even though we wrote a long paper in 2017 on T Pyx alone, it's time
for another - because our audacious claims re the T Pyx/IM Nor
phenomenon (runaway mass transfer, resulting in the binary's death)
could use more scrutiny with new data. There are two important issues
which our new observations could address:
(1) Is the rate of orbital-period increase now the same as it was
pre-outburst, or measurably less?
(2) Has the star's brightness, averaged over many orbits, changed from
the pre-outburst average?
Sunce we observe it a LOT, we don't need a great deal of new data to
address these questions. A few weeks of coverage will do it. Ideally
the runs should be >2.5 hours long, and it would be best if you obtained
some through a V filter, and some through your usual setup (probably
unfiltered or some sort of minus-blue filter). The reason for the V
filter is calibration, of course. The reason for some unfiltered
coverage is to compare it with what you have done in past years.
This sort of approach has a good chance to distinguish between the two
(a) T Pyx is doomed.
(b) T Pyx is just having a bad coughing fit, lasting a few centuries.
This interpretation has been advanced by Brad Schaefer, with some pretty
decent evidence to back it up.
Pyxis is usually reserved for southern observers. But at -32 degrees,
this star is also fine for southern-USA observers, if you plan your
observations around meridian passage, when the star is moving
horizontally. Of course we always dislike airmass - but most of all, we
dislike CHANGES in airmass. (And thanks to those of you who include
airmass in their observing reports.)
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