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Astron. Astrophys. 351, L1-L4 (1999)

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Letter to the Editor

The young detached CO shell around U Camelopardalis

M. Lindqvist 1, H. Olofsson 2, R. Lucas 3, F.L. Schöier 2, R. Neri 3, V. Bujarrabal 4 and C. Kahane 5

1 Onsala Space Observatory, 43992 Onsala, Sweden
2 Stockholm Observatory, 13336 Saltsjöbaden, Sweden
3 IRAM, 300 rue de la Piscine, 38406 St Martin d'Heres Cedex, France
4 Observatorio Astronómico Nacional, Apartado 1143, 28800 Alcalá de Henares, Spain
5 Observatoire de Grenoble, B.P. 53, 38041 Grenoble Cedex 9, France

Received 8 September 1999 / Accepted 11 October 1999

Abstract

We report IRAM Plateau de Bure interferometer observations of the carbon star U Cam in the [FORMULA]([FORMULA]= 1[FORMULA]0) and [FORMULA]([FORMULA]= 2[FORMULA]1) lines. The remarkable images show that U Cam is surrounded by a geometrically thin, [FORMULA]1016 cm, shell of gas at a distance of [FORMULA]6[FORMULA]1016 cm from the star, that expands with a velocity of [FORMULA]23[FORMULA]. The estimated mass of the shell is low, [FORMULA]10[FORMULA]. In addition, we detect emission that peaks at the stellar position. From this we estimate a present mass loss rate and gas expansion velocity of [FORMULA]2.5[FORMULA]10[FORMULA] and 12[FORMULA], respectively. One possible explanation to the structure of the circumstellar medium is that the shell was produced during a very short period, [FORMULA]150 yr, of high mass loss rate, [FORMULA]10[FORMULA], about 800 yr ago. U Cam may fit into the scenario where a helium-shell flash modulates the mass loss rate on short times scales.

Key words: stars: carbon – stars: circumstellar matter – stars: individual: U Cam – stars: mass-loss

Send offprint requests to: M. Lindqvist

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© European Southern Observatory (ESO) 1999

Online publication: November 2, 1999
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