Rotationally excited HD toward Zeta Ophiuchi.
Abstract
Copernicus satellite measurements of HD in J-double prime = 1 and J-double prime = 0 toward Zeta Oph are reported. The ratio of the number densities of HD in the J = 0 and J = 1 states is determined to be 0.15 + or - 0.02 at the 1-sigma level. A value of approximately 24 x 10 to the -17th erg/cu cm per A at 1000 A is obtained for the UV energy density at the Zeta Oph cloud, and the mechanisms for excitation of HD are examined. A tight upper limit is derived for the abundance of HCl, which has been predicted to be present due to the interaction of ionized chlorine with neutral hydrogen. A calculation is performed which indicates that the cloud is 28 pc from the star. It is shown that the two-component cloud model of Black and Dalgarno (1977) with densities of 500 and 2500 H nuclei per cu cm for the outer regions and core, respectively, is in excellent agreement with the observations.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- January 1979
- DOI:
- 10.1086/156755
- Bibcode:
- 1979ApJ...227..483W
- Keywords:
-
- Abundance;
- Hydrogen Clouds;
- Interstellar Matter;
- Satellite Observation;
- Stellar Spectra;
- Born Approximation;
- Electron Transitions;
- Interstellar Extinction;
- Oao 3;
- Spaceborne Astronomy;
- Ultraviolet Radiation;
- Astrophysics;
- Interstellar Matter:Element Abundances;
- Interstellar Molecules