%0 Journal Article %T The Non-thermal Radio Emitter HD 93250 Resolved by Long Baseline Interferometry %+ Institut de Planétologie et d'Astrophysique de Grenoble (IPAG ) %A Sana, H. %A Le Bouquin, J. -B. %A de Becker, M. %A Berger, J. -P. %A de Koter, A. %A Mérand, A. %< avec comité de lecture %J The Astrophysical Journal Letters %V 740 %8 2011 %D 2011 %Z 1110.0831 %Z 2011ApJ...740L..43S %R 10.1088/2041-8205/740/2/L43 %K radiation mechanisms: non-thermal %K stars: early-type %K stars: individual: HD93250 %K stars: massive %K techniques: interferometric %K X-rays: individual: HD93250 %K Astrophysics - Solar and Stellar Astrophysics %K Astrophysics - High Energy Astrophysical Phenomena %Z Sciences of the Universe [physics]Journal articles %X 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 timescales of years suggesting either a single star, a binary system seen pole-on view 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) × 10-3 arcsec. At the distance of Carina, this corresponds to a projected physical distance of 3.5 AU. 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 1 to several years despite the lack of measurable radial velocity variations.
Based on observations collected under program IDs 086.D-0586 and 386.D-0198 at the European Organisation for Astronomical Research in the Southern Hemisphere, Chile. %G English %L insu-03622851 %U https://insu.hal.science/insu-03622851 %~ INSU %~ UNIV-SAVOIE %~ UGA %~ CNRS %~ UNIV-GRENOBLE1 %~ INPG %~ IRSTEA %~ CNES %~ OSUG %~ IPAG %~ AGREENIUM %~ INRAE %~ USMB-COMUE