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Detection of a Hot Binary Companion of $η$ Carinae

Rosina C. Iping·George Sonneborn·Theodore R. Gull·Derck L. Massa·D. John Hillier
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Abstract

We report the detection of a hot companion of $η$ Carinae using high resolution spectra (905 - 1180 Å) obtained with the Far Ultraviolet Spectroscopic Explorer (\fuse) satellite. Observations were obtained at two epochs of the 2024-day orbit: 2003 June during ingress to the 2003.5 X-ray eclipse and 2004 April several months after egress. These data show that essentially all the far-UV flux from \etacar shortward of \lya disappeared at least two days before the start of the X-ray eclipse (2003 June 29), implying that the hot companion, \etaB, was also eclipsed by the dense wind or extended atmosphere of \etaA. Analysis of the far-UV spectrum shows that \etaB is a luminous hot star. The \nii \wll1084-1086 emission feature suggests that it may be nitrogen-rich. The observed far-UV flux levels and spectral features, combined with the timing of their disappearance, is consistent with \etacar\ being a massive binary system.

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Rosina C. Iping, George Sonneborn, Theodore R. Gull, Derck L. Massa, D. John Hillier. 2005-10-19. Detection of a Hot Binary Companion of $η$ Carinae. https://doi.org/10.1086/498268

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