naa a22 4500 510790216 CHVBK 20180411083317.0 cr unu---uuuuu 180411e20131001xx s 000 0 eng 10.1134/S106377371309003X doi (NATIONALLICENCE)springer-10.1134/S106377371309003X Nesterenok A. Ioffe Physical-Technical Institute, ul. Politekhnicheskaya 26, 194021, St. Petersburg, Russia aut H2O maser emission in circumstellar envelopes around AGB stars: Physical conditions in gas-dust clouds [Elektronische Daten] [A. Nesterenok] The pumping of 22.2-GHz H2O masers in the circumstellar envelopes of asymptotic giant branch stars has been simulated numerically. The physical parameters adopted in the calculations correspond to those of the circumstellar envelope around IK Tau. The one-dimensional plane-parallel structure of the gas-dust cloud is considered. The statistical equilibrium equations for the H2O level populations and the thermal balance equations for the gas-dust cloud are solved self-consistently. The calculations take into account 410 rotational levels belonging to the five lowest vibrational levels of H2O. The stellar radiation field is shown to play an important role in the thermal balance of the gas-dust cloud due to the absorption of emission in rotational-vibrational H2O lines. The dependence of the gain in the 22.2-GHz maser line on the gas density and H2O number density in the gas-dust cloud is investigated. Gas densities close to the mean density of the stellar wind, 107−108 cm−3, and a high relative H2O abundance, more than 10−4, have been found to be the most likely physical conditions in maser sources. Pleiades Publishing, Inc., 2013 astrophysical masers nationallicence asymptotic giant branch nationallicence late-type stars nationallicence Astronomy Letters Springer US; http://www.springer-ny.com 39/10(2013-10-01), 717-728 1063-7737 39:10<717 2013 39 11443 https://doi.org/10.1134/S106377371309003X text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1134/S106377371309003X text/html Onlinezugriff via DOI NATIONALLICENCE 100 1- Nesterenok A. Ioffe Physical-Technical Institute, ul. Politekhnicheskaya 26, 194021, St. Petersburg, Russia aut NATIONALLICENCE 773 0- Astronomy Letters Springer US; http://www.springer-ny.com 39/10(2013-10-01), 717-728 1063-7737 39:10<717 2013 39 11443 Metadata rights reserved Springer special CC-BY-NC licence nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-springer