SIMBAD references

Spatially-resolved high-resolution long-slit spectra of Betelgeuse's circumstellar shell are described for a spectral window centered on the 7699Å resonance line of neutral potassium. The Ki emission from resonance fluorescent scattering of photospheric photons which is mapped out to 50 arcsec from the star is approximately spherically symmetric with a brightness decreasing as r^{–2.36±0.03}, where r is the radial distance from the star. Our measurements together with the earlier theoretical interpretation by Rodgers & Glassgold suggest that the mass loss rate is about 2x10^–6M_☉/yr. The Ki emission is far from homogeneous: intensity inhomogeneities are seen down to the seeing limit of about 1 arcsec and the velocity resolution of about 2km/s. There is clear evidence for a thin shell of 50 arcsec radius. This is identified with the weaker circumstellar absorption component known as S2. Estimates are made of the density of K atoms in this shell (≃6x10^–5cm^–3).