[vsnet-chat 1050] RE: CK Ori is constant :-)

[aah@nofs.navy.mil]

  Fraser Farrell wrote that CK Ori appeared to be constant in the
Hipparcos satellite data.  At Hp=6.35, Hipparcos is capable of
millimag accuracy and should certainly see any variability obvious
from the ground.  A range of 6.35-6.38 would normally be considered
variable (though you will find almost all stars vary at the 1 percent
level).  Without researching this star in particular, let
me give a few obvious comments.
  There are many instances of named variables in the GCVS that are
not variables.  An example is V708 Her, but any variable listed without
period or amplitude is suspect.  Many others have such poor
coordinates or misidentifications that a single variable might have
two names, or may be given the coordinates of a nearby star.  The
GCVS is not perfect, but is a good approximation considering the
tens of thousands of listed stars from some pretty unusual references.
I don't envy the author's task!  Especially now, with the new astrometry
and photometry from HIpparcos/Tycho on known variables, their new
variables, the input from the microlensing groups (MACHO, OGLE, etc.),
our FASTT variables, potential new variables from LONEOS, TASS, LOTIS,
ROTSE, etc.
  Hipparcos, due to its scanning nature, did not have good time
sampling for many variable star types.  This is particularly true for
new variables, where period determination is necessary.  There are
many cases of misclassified stars and incorrect periods in the
Hipparcos/Tycho catalogs.
  CK Ori is classified as a low amplitude K giant.  However, upon
casual examination, I did not see any light curve, period, amplitude,
etc. given.  This is always suspicious, plus very few K stars are
variable (real variability sets in about M1).
Arne
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Arne Henden                               Instruments/software/CCDs
US Naval Observatory Flagstaff Station    Cepheids/photometry/IR
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aah@nofs.navy.mil                         FAX:   (520)774-3626

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