The distribution of H13CN in the circumstellar envelope around IRC+10216

Details The distribution of H13CN in the circumstellar envelope around IRC+10216 The distribution of H13CN in the circumstellar envelope around IRC+10216

2007-07-30

arxiv.org/abs/0707.4364v1

Astronomy and Astrophysics

Astrophysics

Accepted for publication in ApJ. 20 pages, 7 figures

Scientific paper

10.1086/522196

H13CN J=8-7 sub-millimetre line emission produced in the circumstellar envelope around the extreme carbon star IRC+10216 has been imaged at sub-arcsecond angular resolution using the SMA. Supplemented by a detailed excitation analysis the average fractional abundance of H13CN in the inner wind (< 5E15 cm) is estimated to be about 4E-7, translating into a total HCN fractional abundance of 2E-5 using the isotopic ratio 12C/13C=50. Multi-transitional single-dish observations further requires the H13CN fractional abundance to remain more or less constant in the envelope out to a radius of about 4E16 cm, where the HCN molecules are effectively destroyed, most probably, by photodissociation. The large amount of HCN present in the inner wind provides effective line cooling that can dominate over that generated from CO line emission. It is also shown that great care needs to be taken in the radiative transfer modelling where non-local, and non-LTE, effects are important and where the radiation field from thermal dust grains plays a major role in exciting the HCN molecules. The amount of HCN present in the circumstellar envelope around IRC+10216 is consistent with predicted photospheric values based on equilibrium chemical models and indicates that any non-equilibrium chemistry occurring in the extended pulsating atmosphere has no drastic net effect on the fractional abundance of HCN molecules that enters the outer envelope. It further suggests that few HCN molecules are incorporated into dust grains.

Affiliated with

Also associated with

No associations

Rating

The distribution of H13CN in the circumstellar envelope around 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 H13CN in the circumstellar envelope around IRC+10216, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and The distribution of H13CN in the circumstellar envelope around IRC+10216 will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFWR-SCP-O-359264