Hi CBAers,Due to the deadline for submitting papers for the SAS/AAVSO meeting (mid-June in Ontario, California), Enrique and I have had to rush something for publication re the still-ongoing outburst of OV Boo. I'm attaching the abstract and author list, and will send the paper within 3 days (to be followed a few months later by a regular-journal submission. If you're an author, send me, and also Enrique: your postal address, telescope aperture, and how many nights/hours you have observed this star. These things are sometimes needed for the eventual paper in a regular journal.
But I wanted to mention now a discovery that really amazed me, in the course of analyzing the data so far. And that is: how accurately we can measure the moments of mid-eclipse. In superoutburst, there is a large elliptical accretion disk which precesses around and modulates the mid-eclipse timing with a 3.9 day period. If it weren't for that, we could do even better. But from the several hundred timings obtained to date, that simple O-C curve, manifesting the 3.9 day period, shows an internal dispersion of just 3.1 seconds. This despite some seemingly formidable problems: integration times are in the range 40-60 seconds... S/N ratio at mid-eclipse is around 5... the white-dwarf eclipse is convolved with the disk eclipse... I only calculate heliocentric corrections accurate to 1-1.5 s. From this I learn:
* CBA observers are very diligent with their time reports * the benefits of "crowd-sourced" data * the benefits of sharp eclipses * CBA observers are intrepid when it comes to faint stars * I should be more careful about heliocentric corrections.We should definitely pay more attention to eclipsers in general, and especially to sharp eclipsers. Accuracy of a few seconds brings into range long-term evolution issues, for which actual observational constraints in CVs have been meager. Gravitational radiation? Magnetic braking (quantitatively)? It requires a lot of persistence, which we definitely have... but not necessarily a lot of aperture, which we don't have.
I'll soon send a list of seasonally-appropriate stars which could be quite good targets. But here's a few which come to mind right away:
Z Cha, OY Car, DV UMa, IY UMa, V1432 Aql, DQ Her, LX Ser.Some degree of fearlessness is an asset here. Who woulda thunk that our little telescopes could get such good data on a mag 18.5 eclipse that lasts 2 minutes? But they can. Best strategy here is to adopt a star and pound it. The dispersion in the timings, as well as the timings themselves, carries critical information.
joe
Attachment:
booaavso.pdf
Description: Adobe PDF document
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