Re: "twins"

[aah@nofs.navy.mil]

john wrote:
>The idea was that hopefully an object in outburst might just have
>sufficiently different photocentre/whatever to appear at a slightly
>different position as an object at quiescence and maybe show up as two
>very close objects.
  Not likely; if you look at the typical periods and typical
distances of outbursting objects like CVs, you will find that the
orbital separation is in the milliarcsec range.
Tom wrote:
>My position is that there are very few twins on the scale of things.  You 
>will have to work hard to convince me to do anything until Arne gets us a 
>catalog with good positions that we can use as a reference.
  This has been given to Michael R.; it will be interesting to see
the result of a master catalog match approach instead of internal
astrometry.  Note that there are at least two ways of getting twins:  poor
astrometry giving positions outside of matching boxes (this can be
improved), and physical doubles with separation around the matching
radius dimension (difficult to do anything about).  The latter ones are
those that I mentioned in the FASTT datasets.  You will get more twins
as you move into the galactic plane.

Arne