ALMA observations of CO ( 1-0 ) and CO ( 2-1 ) emissions of the circumstellar envelope of EP Aqr , an oxygen-rich AGB star , are reported .
A thorough analysis of their properties is presented using an original method based on the separation of the data-cube into a low velocity component associated with an equatorial outflow and a faster component associated with a bipolar outflow .
A number of important and new results are obtained concerning the distribution in space of the effective emissivity , the temperature , the density and the flux of matter .
A mass loss rate of ( 1.6 \pm 0.4 ) 10 ^ { -7 } solar masses per year is measured .
The main parameters defining the morphology and kinematics of the envelope are evaluated and uncertainties inherent to de-projection are critically discussed .
Detailed properties of the equatorial region of the envelope are presented including a measurement of the line width and a precise description of the observed inhomogeneity of both morphology and kinematics .
In particular , in addition to the presence of a previously observed spiral enhancement of the morphology at very small Doppler velocities , a similarly significant but uncorrelated circular enhancement of the expansion velocity is revealed , both close to the limit of sensitivity .
The results of the analysis place significant constraints on the parameters of models proposing descriptions of the mass loss mechanism , but can not choose among them with confidence .