[vsnet-chat 5058] Re: Variable stars in OGLE-II field

[aah@nofs.navy.mil]

Kato-san's example of V1417 Sgr is not the best choice.
If you look at the B. Blanco paper (AJ 89, 1836, 1984),
she writes: "A chart has been included for one star, G264,
which was first thought to be an eclipsing variable (hence
its designation E6), but no variation greater than 0.2mag
could be detected in the final measurements."  The position
she gives is the one shown for V1417 Sgr in Simbad and presumably
used in the GCVS.  I don't think this star matches either star
posted by Kato since those two stars have B>20, and V1417 Sgr
has B~16.
  Bulge fields are notoriously difficult, and since the
GCVS team is systematically going through the catalog to
update coordinates, I bet they have not reached Sgr yet.
Good luck when they do!
  Certainly the GCVS contains a fraction of nonvariable stars,
and an equal fraction of stars with *very* wrong coordinates.
Our FASTT variable star paper identified several stars with
coordinate errors greater than an arcminute, which would be
almost impossible to locate in Sgr.  Then there is always
proper motion, a not-insignificant error when you are dealing
with dense fields.  The final answer in many
cases is going to be the large surveys, such as ROTSE or
LONEOS, when they publish their final lists of variable stars.
Then cross-checking will find most of the 'constant' stars,
and classification/magnitude will find most of the stars with incorrect
coordinates.  Luckily most of the early photographic surveys,
where most of the errors occur, had bright limiting magnitudes
and so will be easier to find the discrepant stars.
Arne

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