  We present results of high-resolution radio continuum observations towards
the binary star WR 21a (Wack 2134) obtained with the Australia Telescope
Compact Array (ATCA) at 4.8 and 8.64 GHz. We detected the system at 4.8 GHz (6
cm) with a flux density of 0.25+-0.06 mJy and set an upper limit of 0.3 mJy at
8.64 GHz (3 cm). The derived spectral index of alpha < 0.3
[S(nu)=k.nu**(alpha)] suggests the presence of non-thermal emission, probably
originating in a colliding-wind region. A second, unrelated radio source was
detected ~10" north of WR 21a at (RA, Dec)(J2000)=(10h 25m 56.49, -57deg 48'
34.4", with flux densities of 0.36 and 0.55 mJy at 4.8 and 8.64 GHz,
respectively, resulting in alpha = 0.72. HI observations in the area are
dominated by absorption against the prominent HII region RCW 49. Analysis of a
complete set of archived X-ray observations of WR 21a confirms its strong
variability but throws into doubt previous suggestions by Reig (1999) of a
period of years for the system. Finally, we comment on the association with the
nearby EGRET source 3EG J1027-5817.
