(cba:news) QS UMa

[Joe Patterson]

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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