  We present the results of radio continuum observations towards the open
cluster Tr 14, where our main targets are the early-type O stars HD 93129A/B
and HD 93128. The observations were carried out at 3 cm (8.64 GHz) and 6 cm
(4.80 GHz) with the Australia Telescope Compact Array. Only HD 93129A (type O2
If*) was detected; we measure flux densities of S_(3cm) = 2.0 +- 0.2 mJy and
S_(6cm) = 4.1 +- 0.4 mJy. The resulting spectral index of alpha = -1.2 +- 0.3
(S_(nu) = k . nu^alpha) indicates predominantly non-thermal emission,
suggesting HD 93129A may be a binary system. We propose that the observed 3 cm
radio emission is mostly coming from the non-thermal wind collision region of a
binary, and, to a lesser extent, from the thermal winds of the primary and
secondary stars in HD 93129A. At a stellar distance of 2.8 kpc, we derive a
mass-loss rate M_dot = 5.1 x 10^(-5) M_sun/yr, assuming the thermal fraction of
the 3 cm emission is about 0.5.
