[vsnet-chat 3673] Re: fast variations in mira stars

["Ondrej Pejcha" <opejcha@volny.cz>]

Dear all,

I've read mentioned L. Smelcer's article. It is a short
notice translated from P. Maffei and G. Tosti, AJ, 6, June
95 (the precise meaning of citation remains unclear to me).
Translation from Czech to English:

Short-term variations with amplitude greater than 0,5 mag
were observed in 18 LPVs during study of a sample of 182
LPVs in M16 and M17 regions. Photographic I and B plates
were used and time span covers 1961-1991. These phenomenons
lasted 1 to 30 days and can be divided into following:
a) rapid brightening or dimming
b) *same as above but with different formulation*
c) flickering
End

L. Smelcer does CCD V photometry of Miras (mainly of those
which change period) and some SRVs for MEDUZA group. His
production is more than 2000 measurements per year. This
allows very good comparison of visual observations and CCD
measurements. This shows that systematic differences between
CCD and eye really exists (but only in very few cases, which
is quite surprising). This difference has two reasons:
- different spectral response of human eye and CCD
- wrong values of comparison stars; this happened in case of
V360 Cyg and caused difference 0,5 mag.

Another good work on "Reliability of visual observations"
was done by Petr Sobotka in his thesis. It can be downloaded
via http://astro.sci.muni.cz/variables/meduza/bak.pdf
(unfortunately only Czech without Englich abstract, but
figures are quite interesting).
I think Petr can write some further info regarding current
topic.

Best regards,
Ondrej Pejcha

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