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(cba:news) T Pyx 2020-1 (Joe Patterson) [2020-12-05T13:51:08Z]


Hi CBAers,
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 leading interpretations:
(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.)

joe
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