New Lines of Ethylene and a Search for Methylene in IRC +10216
Abstract
Seven new lines in the 10 micron nu7 band of C2H4 have been detected in the highly obscured carbon star IRC + 10216. The line intensities cannot be well described by a single rotational temperature, in contrast to the lines of CH4 and SiH4 previously observed in this source. There are at least three interpretations: the line intensities are variable on a time scale of months and years, C2H4 lines are formed over a region less homogeneous than that of CH4 and SiH4, or ethylene is somewhat nonthermally excited. Regardless, the line intensities indicate an average rotational temperature of 100 K and a column density of about 4 x 10 to the 15th/sq cm, which is approximately 2 x 10 to the -5th times the CO abundance. A search was also made for infrared transitions of CH2, the methylene radical. No lines were detected, but the observational limits are compared with the abundance and radial distribution for CH2 predicted by a model invoking the photodissociation of CH4.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- March 1987
- DOI:
- 10.1086/165066
- Bibcode:
- 1987ApJ...314..356G
- Keywords:
-
- Carbon Stars;
- Ethylene;
- Infrared Astronomy;
- Line Spectra;
- Methylene;
- Stellar Composition;
- Stellar Spectra;
- Abundance;
- Interstellar Matter;
- Stellar Envelopes;
- Astrophysics;
- INFRARED: SPECTRA;
- LINE IDENTIFICATIONS;
- STARS: ABUNDANCES;
- STARS: CARBON;
- STARS: CIRCUMSTELLAR SHELLS;
- STARS: INDIVIDUAL ALPHANUMERIC: IRC;
- 10216