BIPOLAR FLOW IN A SLOWLY EXPANDING CIRCUMSTELLAR ENVELOPE AROUND X-HERCULIS

We report high signal to noise millimeter wave CO observations of the circumstellar envelope around the nearby oxygen-rich Semi-Regular vari able X Her. This envelope is partially resolved by the IRAM 30m telesc ope at 1mm and the line shapes appear narrower and more complex than m ost of the profiles observed towards AGE envelopes. We interpret the C O (1-0) and (2-1) profiles as resulting from three components in the w ind : a very slowly expanding spherical component (v(exp) = 2.5 km s(- 1)) and two higher-velocity components (v(exp) greater than or equal t o 10 km s(-1)). These ''high-velocity'' components are symmetrically d isplaced compared to the slow component and are likely to be the red a nd blue shifted cones of a weakly collimated bipolar flow, probably se en with a small viewing angle (similar to 15 degrees). The bipolar flo w contains between one fifth and one third of the total detected circu mstellar gas mass of about 3 x 10(-4) M.. The mass loss rate in the bi polar flow of about 1 x 10(-7) M. yr(-1) is comparable to the rate in the slowly expanding spherical envelope. The mechanism responsible for non-spherical mass loss is still unclear, but there is strong evidenc e for asymmetries in or very near the stellar photosphere. The asymmet ric flow may be especially conspicuous since the spherical portion of the mass loss has such a low velocity.