ISO LWS Observations of H2O from R Cas: A Consistent Model For Its Circumstellar Envelope
Omont, A.; Barlow, M. J.; Cox, P.; Lim, T.; Nguyen-Q-Rieu; Sylvester, R. J.; Skinner, C. J.; Truong-Bach; Liu, X. W.
France, United Kingdom, Spain, United States
Abstract
We present an ISO LWS 43-197 µm grating spectrum of the oxygen-rich AGB star R Cas. The spectrum is rich of isolated and blended H2O lines. For their identification and in order to determine the physical parameters of the circumstellar envelope, we have constructed a model which treats radiative transfer, chemical exchange and photodissociation reactions, and various heating and cooling processes in a consistent manner. By fitting the observed line fluxes and using stellar parameters based upon the Hipparcos distance, we derived a mass-loss rate of M = 1 10-6 M⊙ yr-1 which is close to the value 6 10-7 M⊙ yr-1 previously derived for W Hya, another oxygen-rich AGB star.