The non-thermal radio emitter HD 93250 resolved by long baseline interferometry
Abstract
As the brightest O-type X-ray source in the Carina nebula, HD 93250 (O4 III(fc)) is X-ray overluminous for its spectral type and has an unusually hard X-ray spectrum. Two different scenarios have been invoked to explain its X-ray properties: wind-wind interaction and magnetic wind confinement. Yet, HD 93250 shows absolutely constant radial velocities over time scales of years suggesting either a single star, a binary system seen pole-one or a very long period and/or highly eccentric system. Using the ESO Very Large Telescope Interferometer, we resolved HD 93250 as a close pair with similar components. We measured a near-infrared flux ratio of 0.8+/-0.1 and a separation of 1.5+/-0.2 x 10E-03 arcsec. At the distance of Carina, this corresponds to a projected physical distance of 3.5 A.U. While a quantitative investigation would require a full characterization of the orbit, the binary nature of HD 93250 allows us to qualitatively explain both its X-ray flux and hardness and its non-thermal radio emission in the framework of a colliding wind scenario. We also discuss various observational biases. We show that, due to line-blending of two similar spectral components, HD 93250 could have a period as short as one to several years despite the lack of measurable radial velocity variations.
Keywords
Cite
@article{arxiv.1110.0831,
title = {The non-thermal radio emitter HD 93250 resolved by long baseline interferometry},
author = {H. Sana and J. -B. Le Bouquin and M. De Becker and J. -P. Berger and A. de Koter and A. Merand},
journal= {arXiv preprint arXiv:1110.0831},
year = {2011}
}
Comments
9 pages, 4 figures, published in ApJL