CRL 2688 and CRL 618: Proto--planetary nebulae
Emission from the J=1..-->..0 transition of /sup 12/C/sup 16/ O has been detected at 2.6 mm from the peculiar infrared objects CRL 2688 (the Egg Nebula) and CRL 618. The observed parabolic line-shape can be interpreted as optically thick emission from a uniformly expanding molecular envelope with a size smaller than the telescope beam. The line width indicates an expansion velocity on the order of 20 km s/sup -1/. Other molecular lines similar to those observed in the envelope of the carbon star IRC+10216 are also observed in CRL 2688, even though the central star in CRL 2688 has a relatively early spectral type (F5 Ia). In CRL 618, the existence of an expanding molecular envelope around a central with spectral type BO implies that the central star has evolved within a very short time (<10/sup 4/ years) from a cool, perhaps carbon-rich, star. The presence of mass loss and the rapid evolution of the central stars suggest that CRL 2688 and CRL 618 may be photo--planetary nebulae. It is noted that IRC+10216, CRL 2688, CRL 618, and the planetary nebular NGC 7027 may represent different stages of an evolutionary sequence. Other peculiar objects such as M1-92 (Minkowski's Foot-print), HD 44179 (the Red Rectangle), OH 0739--14, and HD 200775 have also been searched for circumstellar CO emission, but no emission greater than 0.2 K (5 sigma) was detected. (AIP)
- Research Organization:
- Owens Valley Radio Observatory, California Institute of Technology
- OSTI ID:
- 7346158
- Journal Information:
- Astrophys. J., Lett.; (United States), Vol. 205:1
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
GENERAL PHYSICS
PLANETARY NEBULAE
STAR EVOLUTION
CARBON MONOXIDE
CARBON STARS
EMISSION SPECTRA
LINE WIDTHS
MASS TRANSFER
MOLECULES
RADIOWAVE RADIATION
STELLAR ATMOSPHERES
ATMOSPHERES
CARBON COMPOUNDS
CARBON OXIDES
CHALCOGENIDES
ELECTROMAGNETIC RADIATION
NEBULAE
OXIDES
OXYGEN COMPOUNDS
RADIATIONS
SPECTRA
STARS
640105* - Astrophysics & Cosmology- Galaxies
640102 - Astrophysics & Cosmology- Stars & Quasi-Stellar
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