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If you look at the GCVS on-line query, NSV 11500 is indeed
identified as the central star of M57.
See also my article on this subject in 'Sky & Telescope',
September 2001 issue, page 102. If a paper copy is not available,
the main elements are included with more clumsy graphics at:
http://c3po.cochise.cc.az.us/astro/deepsky02.htm
As far as I know, there is no convincing evidence that the central star
is a large-amplitude variable. Probably small (few hundredths) variation
on short timescales would not be surprising, but nothing like the claims
of 19th Century visual observers, who were making mistakes in estimates
due to variable seeing and the bright background of the nebula.
\Brian
Return to the Powerful Daisaku Nogami
vsnet-adm@kusastro.kyoto-u.ac.jp
