Hi CBAers,
Time for an update. As many of you know, many colleges have decided
to go online-only, and we're all scrambling to do this here in NYC.
Quite a challenge to do so with only a few days notice!
So this is just volume 1 of the seasonal target list.
AM CVn. El Magnifico. The 2020 coverage has confirmed the period
change we strongly suspected with all the earlier data. That was the
main goal... and hallelujah, ee got there! But now there is a new
challenge, which we can meet by extending the observing season another
1-2 months.
AM CVn has superhumps at 1011 s and 1051 s (most of the power at 525.5
s). Being superhumps, they flail around somewhat in phase (in
contrast to the stable 1028 s ORBITAL signal). Since both superhumps
are present nearly all the time, one can study their phase wanderings
relative to each other. In "theory", they should be anti-correlated;
one period lengthens while the other shortens. But theory always
yields to data, and in this case even more than usual; when it comes
to accretion-disk precession, "theory" is too respectful a word.
The phase wanderings of the 1011 and 1051 s signals can be readily
tracked with a few (5 would be great) months of time-series
photometry. Long runs are helpful, but not usually necessary. See if
you can grab a 3-4 hour run on AM CVn over the next ~2 months, when it
will be well-placed in the northern sky.
Attached is last year's paper (a prelim version of what we will submit
to the regular journals in a few weeks).
All this beautiful data has made me hungry to try similar analysis on
CR Boo and V803 Cen - the other two bright helium-disk stars. We've
published on each before, but never extensively. So those are
high-priority stars for the next month!
We've had a good year on HZ Pup - definitely enough to publish (for
the first time, re this star). But just to make sure we can bridge to
the next observing season, try to get a few more runs over the next 2
weeks or so.
FULL MOON SPECIAL. SW Sex should be a prime candidate for superhumps,
yet has never shown them. We ought to keep looking - it's getting
very annoying that the star doesn't show them... and also annoying
that we've never done a really thorough search.
joe
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