[vsnet-chat 3909] Re: Astrometry of cataclysmic variables

[Taichi Kato <tkato>]

Re: Astrometry of cataclysmic variables

> All these stars are in quite dense star fields and the positions given in
> SIMBAD can be source of confusion.
> 
> As already said by Arne Henden and Taichi Kato, it is clear that in the
> past astrometry of this kind of objects had not the same consideration as
> today; so, maybe that other CVs (and other kind of variables, of course)
> are actually catalogued with not accutare astrometry. When a good reference
> chart is available this can be a  little problem, but in different cases
> one can be definitely confused.

   The problem of the SIMBAD errors mostly come from the fact they have
not yet (completely) incorporated DWS97.  This is as slow as the GCVS
designate new variables.  This is the reason why I am not very willing
to check SIMBAD as the primary reference for variable stars.

   The case of RX J0459.7+1926 probable has a different origin.  SIMBAD
looks like to return the X-ray position, as could be natural for this
entry name.  The optical counterpart was given accurate coordinates
when it was first published.  There is no ambiguity in it.

   To summarize, most of these objects have proper astrometry in modern
literatures, but are not properly reflected to services/catalogs.

   However, we should encourage astrometry of all such objects, since
this has a chance to provide better astrometry (on better grids),
independent confirmation, and prove chance duplicity or measureable
proper motion.

Regards,
Taichi Kato

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