2004A&A...416..171B

We present the results of radio continuum observations towards the open cluster Tr14, where our main targets are the early-type O stars HD93129A/B and HD93128. The observations were carried out at 3cm (8.64GHz) and 6cm (4.80GHz) with the Australia Telescope Compact Array. Only HD93129A (type O2 If*) was detected; we measure flux densities of S_3cm=2.0±0.2mJy and S_6cm=4.1±0.4mJy. The resulting spectral index of α=-1.2±0.3 (S_ν∝ν^α) indicates predominantly non-thermal emission, suggesting HD93129A may be a binary system. We propose that the observed 3cm 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 HD93129A. At a stellar distance of 2.8kpc, we derive a mass-loss rate {dot}(M)=5.1x10^–5M_☉/yr, assuming the thermal fraction of the 3cm emission is ∼0.5.