Ammonia in C-rich stars

HIFI instrument onboard the Herschel satellite provided an unprecedented number of detections of rotational transitions of ammonia in circumstellar envelopes of evolved stars including massive red supergiants, Asymptotic Giant Branch (AGB), and post-AGB stars. The chemistry of ammonia formation in t...

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Bibliographic Details
Published in:Proceedings of the International Astronomical Union 2018-08, Vol.14 (S343), p.396-397
Main Authors: Etmański, Bartosz, Schmidt, Mirosław R., Yung, Bosco H. K., Szczerba, Ryszard
Format: Article
Language:English
Subjects:
Ammonia
Astronomy
Asymptotic giant branch stars
Atmospheric chemistry
Organic chemistry
Photochemistry
Radiative transfer
Red giant stars
Rotational states
Stellar envelopes
Stellar evolution
Supergiant stars
Thermodynamic equilibrium
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Summary:HIFI instrument onboard the Herschel satellite provided an unprecedented number of detections of rotational transitions of ammonia in circumstellar envelopes of evolved stars including massive red supergiants, Asymptotic Giant Branch (AGB), and post-AGB stars. The chemistry of ammonia formation in the circumstellar envelopes of evolved stars is poorly understood. The mechanisms proposed for its formation are processes behind the shock front, photochemistry in the inner part of the clumpy envelope, and formation on dust grains. We present results of the non-local thermodynamical equilibrium (non-LTE) radiative transfer modeling of ammonia transitions, mainly of the ground-state rotational one NH 3 J K = 1 0 – 0 0 at 572.5 GHz, in selected AGB stars, aiming at the quantitative estimation of the NH 3 abundance. The model of ammonia includes IR radiative pumping via v 2 = 1 vibrational band at 10 μ m.
ISSN:1743-9213
1743-9221
DOI:10.1017/S1743921318006609