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(cba:news) QS UMa (Joe Patterson) [2020-03-11T19:15:21Z]


Oh, and thanks to David Cejudo, we're done with QS UMa for the year!

joe

On 3/11/2020 11:16 AM, Joe Patterson wrote:
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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