Tracing pumping routes in OH
Abstract
We introduce a general method of restoring detailed information about the population flow in molecules under nonlocalthermodynamicequilibrium (NLTE) conditions. This information is usually discarded in numerical algorithms which generate only a solution. We apply the method to tracing the pumping schemes for OH in models that represent three common astrophysical maser environments: the envelopes of asymptoticgiantbranch (AGB) stars, the envelopes of red supergiants, and Galactic starforming regions. In all three of these cases, we show that a large fraction, typically 0.8 or more, of the maser inversion can be recovered from a set of routes that depend on a much smaller fraction (considerably less than 0.1) of the total number of input coefficients to the model. Therefore, these cases display underlying simplicity in the pumping scheme.
 Publication:

Astrophysical Masers and their Environments
 Pub Date:
 March 2007
 DOI:
 10.1017/S1743921307012501
 Bibcode:
 2007IAUS..242...17G
 Keywords:

 masers;
 molecular data;
 molecular processes;
 radiative transfer;
 methods: numerical;
 stars: AGB and postAGB;
 stars: formation