Journal Article

The dust-free symbiotic Mira K4−46 = LL Cas

U. Munari, A. Siviero, S. Dallaporta and A. Frigo

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 407, issue 2, pages 1070-1077
Published in print September 2010 | ISSN: 0035-8711
Published online September 2010 | e-ISSN: 1365-2966 | DOI: http://dx.doi.org/10.1111/j.1365-2966.2010.16886.x
The dust-free symbiotic Mira K4−46 = LL Cas

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Accurate BVRCIC light and colour curves of the Mira variable in the dust-free symbiotic system K4−46 are presented and discussed. They cover several consecutive pulsations cycles. The Mira mean period is 284.2 d, the reddening sums to E(BV) = 0.35 and the distance is 10 kpc. Absolute spectrophotometry at both maximum and minimum brightness of the Mira is presented. The rich emission line and continuum spectrum of the H ii region ionized by the hard radiation of the white dwarf dominates at Mira minimum. From its photoionization analysis, it is found that the H ii region extends to a radius of 210 au, has a mass 1.8 × 10−4 M and it is ionized by a white dwarf of 158 000 K temperature and 0.06 R radius, stably burning hydrogen at its surface. The derived [Fe/H]=−0.45 well match the ambient metallicity expected at K4−46 at its 15 kpc galactocentric distance, and the overabundances in N, Ne and He are those expected if the H ii region is fed by the wind of the Mira and polluted by nuclearly processed material lost by the white dwarf companion.

Keywords: stars: AGB and post-AGB; binaries: symbiotic; stars: individual: LL Cas

Journal Article.  5046 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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