Radio observations of HD 93129A: The earliest O star with the highest mass loss?
Abstract
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 S3 cm = 2.0 ± 0.2 mJy and S6 cm = 4.1 ± 0.4 mJy. The resulting spectral index of α = -1.2 ± 0.3 (Sν ∝ να) 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⊙ = 5.1 × 10-5 M⊙ yr-1, assuming the thermal fraction of the 3 cm emission is ∼0.5.
- Publication:
-
Astronomy and Astrophysics
- Pub Date:
- March 2004
- DOI:
- 10.1051/0004-6361:20034138
- arXiv:
- arXiv:astro-ph/0312003
- Bibcode:
- 2004A&A...416..171B
- Keywords:
-
- stars: individual: HD 93129A;
- HD 93129B;
- HD 93128;
- stars: mass-loss;
- stars: winds;
- outflows;
- radio continuum: stars;
- Astrophysics
- E-Print:
- 9 pages, 3 figures, accepted in A&