%0 Journal Article %T The extended molecular envelope of the asymptotic giant branch star ¦Ð1 Gruis as seen by ALMA - I. Large-scale kinematic structure and CO excitation properties %A C. Paladini %A E. De Beck %A F. Kerschbaum %A L. Doan %A M. Lindqvist %A M. Maercker %A M. Wittkowski %A S. H£¿fner %A S. Mohamed %A S. Ramstedt %A W. H. T. Vlemmings %J - %D 2017 %R 10.1051/0004-6361/201730703 %X Context. The S-type asymptotic giant branch (AGB) star ¦Ð1 Gru has a known companion at a separation of 2.£¿7 (¡Ö400 AU). Previous observations of the circumstellar envelope (CSE) show strong deviations from spherical symmetry. The envelope structure, including an equatorial torus and a fast bipolar outflow, is rarely seen in the AGB phase and is particularly unexpected in such a wide binary system. Therefore a second, closer companion has been suggested, but the evidence is not conclusive.Aims. The aim is to make a 3D model of the CSE and to constrain the density and temperature distribution using new spatially resolved observations of the CO rotational lines.Methods. We have observed the J = 3¨C2 line emission from 12CO and 13CO using the compact arrays of the Atacama Large Millimeter/submillimeter Array (ALMA). The new ALMA data, together with previously published 12CO J = 2¨C1 data from the Submillimeter Array (SMA), and the 12CO J = 5¨C4 and J = 9¨C8 lines observed with Herschel/Heterodyne Instrument for the Far-Infrared (HIFI), is modeled with the 3D non-LTE radiative transfer code SHAPEMOL.Results. The data analysis clearly confirms the torus-bipolar structure. The 3D model of the CSE that satisfactorily reproduces the data consists of three kinematic components: a radially expanding torus with velocity slowly increasing from 8 to 13£¿km£¿s-1 along the equator plane; a radially expanding component at the center with a constant velocity of 14£¿km£¿s-1; and a fast, bipolar outflow with velocity proportionally increasing from 14£¿km£¿s-1 at the base up to 100£¿km£¿s-1 at the tip, following a linear radial dependence. The results are used to estimate an average mass-loss rate during the creation of the torus of 7.7£¿¡Á£¿10-7£¿M¡Ñ£¿yr-1. The total mass and linear momentum of the fast outflow are estimated at 7.3£¿¡Á£¿10-4£¿M¡Ñ and 9.6£¿¡Á£¿1037£¿g£¿cm£¿s-1, respectively. The momentum of the outflow is in excess (by a factor of about 20) of what could be generated by radiation pressure alone, in agreement with recent findings for more evolved sources. The best-fit model also suggests a 12CO/13CO abundance ratio of 50. Possible shaping scenarios for the gas envelope are discussed %U https://www.aanda.org/articles/aa/full_html/2017/09/aa30703-17/aa30703-17.html