Reference : The Non-thermal Radio Emitter HD 93250 Resolved by Long Baseline Interferometry
Scientific journals : Article
Physical, chemical, mathematical & earth Sciences : Space science, astronomy & astrophysics
The Non-thermal Radio Emitter HD 93250 Resolved by Long Baseline Interferometry
Sana, H. [ > > ]
Le Bouquin, J.-B. [ > > ]
De Becker, Michaël mailto [Université de Liège - ULg > Département d'astrophys., géophysique et océanographie (AGO) > Département d'astrophys., géophysique et océanographie (AGO) >]
Berger, J.-P. [ > > ]
de Koter, A. [ > > ]
Mérand, A. [ > > ]
Astrophysical Journal Letters
IOP Publishing
Yes (verified by ORBi)
United Kingdom
[en] radiation mechanisms: non-thermal ; stars: early-type ; stars: individual: HD93250 ; stars: massive ; techniques: interferometric
[en] 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.
Researchers ; Professionals

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