Double Stars in the UCAC4 and not in the WDS

A computer search of all stars in the UCAC4¹ for binary stars has been done. The criteria used to distinguish a binary from other pairs was:

• The stars needed to be closer than ((204.75 / mv) - 12.75) arc seconds, where mv is the brightness of the primary. This is based on a guess by R. Aitken, in 1911.²
• The secondary is no more than 2 magnitudes fainter than the primary.
• The difference between the primary's proper motion and the secondary's proper motion is less than 1/3 of the proper motion of the pair overall.
• There is no Washington Double Star Catalog (WDS)³ star within a minimum of 31 arc seconds of the binary. If the stars are more than 31 arc seconds apart, this separation is used as the WDS search radius.

The pairs found were then manually examined using the Aladin⁴ program. If a pair seemed to be a member of a (usually unlisted) cluster, or if the star(s) in the UCAC4 were not seen on the photograph of the binary, it was removed from the list. The position angles (θ) and separations (ρ) of the binaries were taken using Aladin's "dist" function.

The list of 173 new binaries can be found here.

References

1) UCAC4 main page

2) Abstract of Aitken's article.

3) WDS main page

4) Aladin