Radio observations of HD 93129A: The earliest O star with the highest mass loss?

• Autores: Benaglia, Paula; Koribalski, B.
• Año de publicación: 2004
• Idioma: inglés
• Tipo de recurso: artículo
• Materia: Ciencias Astronómicas; Radio continuum: stars; Stars: individual: HD 93129A, HD 93129B, HD 93128; Stars: mass-loss; Stars: winds, outflows
• Institución: Universidad Nacional de La Plata

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 α = -1.2 ± 0.3 (S_v ∝ v^α) 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.
Facultad de Ciencias Astronómicas y Geofísicas
Instituto Argentino de Radioastronomía