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Astron. Astrophys. 360, L9-L12 (2000)

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Letter to the Editor

The structure and momentum of multiple collimated outflows in the protoplanetary nebula Frosty Leo

R. Sahai 1, V. Bujarrabal 2, A. Castro-Carrizo 2 and A. Zijlstra 3

1 California Institute of Technology, Jet Propulsion Laboratory, MS 183-900, Pasadena, CA 91109, USA
2 Observatorio Astronómico Nacional, Ap. 1143, 28800 Alcalá de Henares, Spain
3 UMIST, Department of Physics, PO Box 88, Manchester M60 1QD, UK

Received 26 April 2000 / Accepted 26 June 2000


We have discovered multiple jet-like features in the inner regions of the protoplanetary nebula (PPN) Frosty Leo, in optical images obtained with the Hubble Space Telescope. Frosty Leo is only the second PPN (after CRL2688) and the first oxygen-rich one, to show well-focussed jets close to the equatorial plane. The nebula consists of two bright compact structures embedded inside two large tenuous bubbles, separated by a flaring, roughly edge-on disk. The relatively high surface brightnesses of two ansae and substructures in the jets imply that the latter have carved out holes in the optically thick central region of the nebula, allowing starlight to escape with very little attenuation. Millimeter-wave CO line observations with the IRAM 30m radiotelescope show the presence of slow ([FORMULA]10 km s-1) and fast ([FORMULA]50 km s-1) components in a molecular outflow associated with the bright inner ([FORMULA]) regions of the nebula. The mechanical momentum in the fast outflow is about a factor 500 larger than that available from the stellar radiation ([FORMULA]) during the post-AGB life of the source, and most likely derives from the gravitational energy of a close binary central star.

Key words: stars: AGB and post-AGB – stars: mass-loss – ISM: reflection nebulae – ISM: individual objects:

Send offprint requests to: Raghvendra Sahai

© European Southern Observatory (ESO) 2000

Online publication: August 17, 2000