|
|
- J. Cernicharo, A. M. Heras, A.G.G.M. Tielens,
J. R. Pardo.
F. Herpin, M. Guelin, and L.B.F.M. Waters
"ISO's discovery of C4H2, C6H2 and of
benzene in CRL 618"
Astrophysical Journal Letters, 546, 2/2, L123-L126 (2001).
We report on the detection with the Infrared Space Observatory
(ISO), for the first time in the circumstellar medium, of
the poli-acetylenic
chains C4H2 and C6H2 and of benzene (C6H6) in the
direction of the protoplanetary nebula CRL618.
Surprisingly,
the abundances of di- and tri-acetylene are only a factor 2-4 lower
than that of C2H2. Benzene is ~ 30 times less abundant than
acetylene.
We suggest that the chemistry in CRL618 has been strongly
modified by the UV photons coming from the hot central star and by
the shocks associated with its high velocity winds.
All the infrared bands arise from a region with kinetic temperatures
between 200-250 K, probably the PDR associated with the dense
torus which surrounds the central star.
C4H2 and C6H2 have also been detected
in CRL2688 so that it seems that C-rich proto-planetary nebula are
the best organic chemistry factories in the space.
|