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- Multi-wavelength diagnostics of massive binary interaction in Eta Carinae
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Multi-wavelength diagnostics of massive binary interaction in Eta Carinae
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Abstract
Eta Car is generally accepted to be a binary system comprised of two massive stars with a total luminosity of Ltot ≥ 5 × 106 Lo and total mass of at least 110 Mo. Most authors agree on a high eccentricity (e ~ 0.9) and an orbital period of 2022.7 ± 1.3 days, but light from the companion star has never been unambiguously observed, causing a large uncertainty in the individual masses and in the other orbital parameters such as the orbital inclination and longitude of periastron. We developed two-dimensional radiative transfer models of Eta Car which account for the presence of the low-density cavity and wind-wind interaction zone created by the rarified, fast wind of the companion, as predicted by hydrodynamical simulations. By comparing synthetic line profiles with available observations, we show that the cavity in the dense wind of the primary star strongly affects multi-wavelength diagnostics such as the ultraviolet spectrum, the optical hydrogen lines, and the shape of the near-infrared continuum region. All these diagnostics have been previously interpretedas requiring a latitude-dependent wind generated by a fast-rotating primary star. Ultimately we found that the presence of the companion hampers the determination of the rotational velocity of the primary.
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About: Jose Groh
Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, D-53121 Bonn, Germany, jgroh@mpifr.de