Journal Article

Discovery of the first symbiotic star in NGC 6822*

Alexei Y. Kniazev, Petri Väisänen, Patricia A. Whitelock, John W. Menzies, Michael W. Feast, Eva K. Grebel, David A. H. Buckley, Yas Hashimoto, Nicola Loaring, Encarni Romero-Colmenero, Ramotholo Sefako, Eric B. Burgh and Kenneth Nordsieck

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 395, issue 2, pages 1121-1126
Published in print May 2009 | ISSN: 0035-8711
Published online April 2009 | e-ISSN: 1365-2966 | DOI:
Discovery of the first symbiotic star in NGC 6822*

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We report the discovery of the first symbiotic star (V= 21.6, KS= 15.8 mag) in the Local Group dwarf irregular galaxy NGC 6822. This star was identified during a spectral survey of Hα emission-line objects using the Southern African Large Telescope during its performance-verification phase. The observed strong emission lines of H i and He ii suggest a high electron density and T* < 130 000 K for the hot companion. The infrared colours allow us to classify this object as an S-type symbiotic star, comprising a red giant losing mass to a compact companion. The red giant is an asymptotic giant branch (AGB) carbon star, and a semiregular variable, pulsating in the first overtone with a period of 142 d. Its bolometric magnitude is Mbol=−4.4 mag.

We review what is known about the luminosities of extragalactic symbiotic stars, showing that most, possibly all, contain AGB stars. We suggest that a much larger fraction of Galactic symbiotic stars may contain AGB stars than was previously realized.

Keywords: binaries: symbiotic; stars: mass-loss; galaxies: individual: NGC 6822

Journal Article.  4264 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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