[vsnet-chat 3829] re GK Per period analysis

[crawl@zoom.co.uk]

>    I just did the analysis, using visual observations reported to VSNET.
>A total of 2425 observations between 1994 July 16 and 2000 November 26
>(disregarding the outburst parts) were used.

Thanks!

>    The PDM analysis show the clear presence of the periodicity related
>to the orbital motion.  The best period determined from these visual
>observations is 1.99673 d, which is close to the published spectroscopic
>period 1.996803 +/- 0.000007 d (Crampton et al. 1996, ApJ 300, 788).
>
>    http://ftp.kusastro.kyoto-u.ac.jp/pub/vsnet/Novae/GK_Per/pdm.gif
>
>    The phase-averaged light curve using Crampton et al.'s period and
>phase (the zero phase is defined as the inferior conjunction of the
>secondary) clearly shows doubly humped profile, which could be interpreted
>as the ellipsoidal variation (or some sort of disk asymmetry?)
>
>    http://ftp.kusastro.kyoto-u.ac.jp/pub/vsnet/Novae/GK_Per/ph.gif

Note to professional astronomers re visual datasets "There's gold in them
thar hills!!!" [Hey, and I mean that, there's been some ill founded and
half arsed snide comments a-lately re visual obs on some lists from some
folk].

>    There seems to be a finite positive O-C to Crampton et al.'s ephemeris.
>The expected eclipse at phase zero was not apparent.

Ah, but does that disappear for your data if you use the period _you_
derived with Crampton's base epoch?????  Then again, finite positive O-C?
If my memory serves, that's declining period?  Possibly expected on
theoretical grounds post-nova?  Then again, again, I don't actually have
any idea of the evolutionary timescale of subgiants either, but I'm sure
it's not on the century level.

Anyway, thanks again... ...interesting!!!

John

Greaves
UK

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