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arXiv · 1705.06469

Resolving the H-alpha-emitting Region in the Wind of Eta Carinae

Ya-Lin Wu·Nathan Smith·Laird M. Close·Jared R. Males·Katie M. Morzinski
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Abstract

The massive evolved star Eta Carinae is the most luminous star in the Milky Way and has the highest steady wind mass-loss rate of any known star. Radiative transfer models of the spectrum by Hillier et al. predict that H-alpha is mostly emitted in regions of the wind at radii of 6 to 60 AU from the star (2.5 to 25 mas at 2.35 kpc). We present diffraction-limited images (FWHM ~25 mas) with Magellan adaptive optics in two epochs, showing that Eta Carinae consistently appears ~2.5 to 3 mas wider in H-alpha emission compared to the adjacent 643 nm continuum. This implies that the H-alpha line-forming region may have a characteristic emitting radius of 12 mas or ~30 AU, in very good agreement with the Hillier stellar-wind model. This provides direct confirmation that the physical wind parameters of that model are roughly correct, including the mass-loss rate of 10^-3 M_sun/yr, plus the clumping factor, and the terminal velocity. Comparison of the H-alpha images (ellipticity and PA) to the continuum images reveals no significant asymmetries at H-alpha. Hence, any asymmetry induced by a companion or by the primary's rotation do not strongly influence the global H-alpha emission in the outer wind.

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Ya-Lin Wu, Nathan Smith, Laird M. Close, Jared R. Males, Katie M. Morzinski. 2017-05-18. Resolving the H-alpha-emitting Region in the Wind of Eta Carinae. https://doi.org/10.3847/2041-8213%2Faa70ed

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