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The role of HeH+ in cool helium rich white dwarfs

G. J. Harris·A. E. Lynas-Gray·S. Miller·J. Tennyson
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Abstract

HeH$^+$ is found to be the dominant positive ion over a wide range of temperatures and densities relevant to helium rich white dwarfs. The inclusion of HeH$^+$ in ionization equilibrium computations increases the abundance of free electrons by a significant factor. For temperatures below 8000 K, He$^-$ free-free absorption is increased by up to a factor of 5, by the inclusion of HeH$^+$. Illustrative model atmospheres and spectral energy distributions are computed, which show that HeH$^+$ has a strong effect upon the density and pressure structure of helium rich white dwarfs with teff < 8000 K. The inclusion of HeH$^+$ significantly reddens spectral energy distributions and broad band color indices for models with Teff < 5500 K. This has serious implications for existing model atmospheres, synthetic spectra and cooling curves for helium rich white dwarfs.

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G. J. Harris, A. E. Lynas-Gray, S. Miller, J. Tennyson. 2004-11-12. The role of HeH+ in cool helium rich white dwarfs. https://doi.org/10.1086/427391

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