The ISO/LWS spectrum of the EGG nebula, AFGL 2688.
Omont, A.; Ade, P. A. R.; Burgdorf, M.; Serra, G.; Griffin, M. J.; Barlow, M. J.; Caux, E.; Cernicharo, J.; Cohen, M.; Liu, X. -W.; Cox, P.; Swinyard, B. M.; Molinari, S.; di Giorgio, A.; Lim, T.; Gonzalez-Alfonso, E.; Sidher, S.; Lorenzetti, D.; Nisini, B.; Texier, D.; Unger, S. J.; Saraceno, P.; Clegg, P. E.; Armand, C.; Furniss, I.; Glencross, W. M.; Gry, C.; King, K. J.; Orfei, R.; Nguyen-Q-Rieu; Trams, N.; Baluteau, J. -P.; Emery, R. J.; Joubert, M.; Pequignot, D.; Skinner, C. J.; Towlson, W. A.; Eward, D.
Abstract
We present an ISO Long Wavelength Spectrometer (LWS) grating spectrum of the carbon-rich proto-planetary nebula AFGL 2688 between 43 and 194μm. 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 [O I] and [C II] 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 ~400K.