Observations of the circumstellar ammonia in carbon-rich AGB stars by Herschel/HIFI instument.
Ammonia has been found to exists in circumstellar envelopes of evolved stars in amounts that exceed predictons of the current chemical models for both O-rich and C-rich AGB stars. HIFI instrument clearly detected the ground-state rotational transition NH3 J(K)=1,0-0,0 at 572.5 GHz in envelopes of six C-rich AGB stars, including earlier detection in IRC+10216, and nine transitions between the lowest rotational levels in IRC+10216. We present results of the non-LTE radiative transfer modelling conducted with the goal to derive NH3 abundances in these sources. The model of ammonia includes IR radiative pumping via v2=1 vibrational band at 10 micormeter. Theoretical predictions of the model are applied for the analysis of excited rotational ammonia lines available for some of the sources, in particular for IRC+10216.
Ostatnia aktualizacja: 17.05.2016 14:46