[vsnet-chat 1055] CK Ori etc.

[Taichi Kato <tkato>]

   According to the first edition of the GCVS (fortunately here!), CK Ori
is cataloged as SR? having a range of 6.2-6.7v, and a period of 120? d.
No reference is given.  This star was likely to be studied by visual
observations.

   I suppose visual observers have used the comparison star HD35762 = SAO
112781, for which mag 6.6 is usually assigned in several variable star
charts (this mag 6.6 may have originated from the HD magnitude 6.61;
modern photometry gives V=6.75).  I also use this comparison star when
observing CK Ori.  The problem may be that this comparison star, looking
suitable to the eye, is very blue (B-V=-0.17, Tycho).  This difference
in color may have caused potential variation to human eyes.

   Another interesting K-type "cst" star is CI Ori, which was already
assigned as "Cst" in GCVS 1st, referring to Ashbrook's manuscript.  The
description in magnitude (5.0v) also suggests the variability was checked
visually.

   Yet another K-type "cst" star, once claimed of variability by visual
(and photographic!) observations and designated, is IS Gem.  Hipparcos
reports no variability, while visual and photographic observations have
recorded an amplitude of 0.7 mag(!).  The large (10.6mas) Hipparcos parallax
suggests the star to be less luminous than quoated in GCVS (K3II).
Has anyone more comments on this star?

   Intermediate case: S Eri, once discarded as "cst", later revival as
RRC: having an amplitude of 4.77-4.80 V (photoelectric) and a period of
0.273 d (from GCVS 4), was observed constant by Hipparcos.

Regards,
Taichi Kato

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