Astronomy and Astrophysics Letters dedicated to ISO

The ISO/LWS spectrum of the Egg nebula, AFGL 2688

P. Cox - E. González-Alfonso - M.J. Barlow - W. Liu - T. Lim - B.M. Swinyard - J. Cernicharo - A. Omont - E. Caux - C. Gry - M.J. Griffin - J.-P. Baluteau - P.E. Clegg - S. Sidher - D. Péquignot - Nguyen-Q-Rieu - K.J. King et al.


We present an ISO Long Wavelength Spectrometer (LWS) grating spectrum of the carbon-rich proto-planetary nebula AFGL 2688 between 43 and 194 microns. The far-infrared spectrum of AFGL 2688 is dominated by strong rotational transitions of CO which are detected from J=14-13 up to J=23-22. The atomic fine structure lines [OI] and [CII] are not detected. This is consistent with the cool central star of AFGL 2688 not having yet photodissociated the molecular gas ejected during the AGB phase. The far-infrared CO emission in AFGL 2688 appears to originate in shocked dense gas at a temperature of ~ 400 K.

planetary nebulae: general - planetary nebulae: individual (AFGL 2688) - interstellar medium: molecules

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