Other
Scientific paper
Feb 1995
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1995apj...439..996d&link_type=abstract
The Astrophysical Journal, Part 1 (ISSN 0004-637X), vol. 439, no. 2, p. 996-1010
Other
37
Carbon Stars, Cyanides, Hydrocyanic Acid, Molecular Spectra, Stellar Composition, Stellar Envelopes, Abundance, Fourier Transformation, Image Analysis, Radio Interferometers, Stellar Models, Synthetic Apertures
Scientific paper
We present aperture synthesis images of millimeter-wavelength molecular emission lines of HCN (J = 1-0 at 88.6 GHz), H(13)CN )J = 1-0 at 86.3 GHz), and CN (N = 1-0, J = 3/2-1/2 at 113.5 GHZ) toward the carbon star IRC + 10216. The HCN and H(13)CN images were made with the Berkeley-Illinois-Maryland Array (BIMA) interferometer, while the CN images were from a combination of interferometer and single-dish data. The HCN and H(13)CN images have an angular resolution of 8 arcseconds and a velocity resolution of approximately 1.3 km/s; the CN images have an angular resolution of 11 arcsecs and a velocity resolution of approximately 0.9 km/s. The images show that the HCN and H(13)CN are found concentrated toward the center of the envelope, while CN is found in the shell surrounding the central star. The data for HCN and H(13)CN are compared with the output of a statistical equilibrium code, which takes into account the excitation by IR photons and collisions with H2, and calculates the radial brightness profiles and spectra. The models are used to determine the abundance distribution of H(13)CN. HCN is too optically thick for accurate modeling; we infer the HCN abundance by scaling H(13)CN up by a factor of 40. For CN, a simple Local Thermodynamic Equilibrium (LTE) calculation is used to derive the abundance of the molecule as a function of distance form the star. The distributions of HCN and CN are qualitatively consistent with chemical models for asymptotic giant branch (AGB) star envelopes. Our best estimate of the peak CN/HCN abundance ratio is about 0.12, and the radius of the peak CN abundance is 19 arcsecs from the star. Both of these values are significantly less than recent photochemical model predictions. We suggest that CN phtodissociates or reacts with other radicals or ions more rapidly than these models assume.
Bieging John H.
Dayal Aditya
No associations
LandOfFree
The distribution of HCN, H(13)CN, and CN in IRC + 10216 does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with The distribution of HCN, H(13)CN, and CN in IRC + 10216, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and The distribution of HCN, H(13)CN, and CN in IRC + 10216 will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-1630711