Simulating H2O Maser Emission in the Mass Outflows from Evolved Stars |
| |
| Authors: | J A Yates E M L Humphreys A M S Richards |
| |
| Institution: | (1) University of Hertforshire, College Lane, Hatfield, Herts., UK;(2) School of Chemistry, University of Bristol, Bristol, UK;(3) Liverpool John Moores University, Liverpool, UK |
| |
| Abstract: | The combination of a time-dependent spherically symmetric hydrodynamic model of stellar atmosphere pulsation and a radiation
transport code, which incorporates maser saturation theory, enabled us to synthesise maps and spectra of H2O maser emission from the circumstellar envelopes of long period variable stars.
The synthetic maps and spectra compare favourably with observed 22, 321 and 325 GHz H2O maser emission. As is observed in H2O maser regions the peak emission occurs between 3–8 stellar radii from the star. The calculated H2O maser regions are in conditions of nH2 = 106 − 108 cm−3, assuming a fractional abundance of 10−4; kinetic temperatures of 550–3000 K; dust ensemble temperatures of 500–1200 K and an accelerating velocity field. The IR
radiation field is explicitly included in the radiation transport model, incorporating the latest absorption efficiency data
for silicates from Draine. We reproduce the features seen in high angular resolution MERLIN spectral line datacubes. This
shows that a mass outflow model which extends the photosphere using pulsations and incorporates radiation pressure on silicate
based dust particles can produce the observed data on small (10-mas) angular scales.
This revised version was published online in September 2006 with corrections to the Cover Date. |
| |
| Keywords: | |
| 本文献已被 SpringerLink 等数据库收录！ |
|
