1996A&A...310..952K

We report high signal to noise millimeter wave CO observations of the circumstellar envelope around the nearby oxygen-rich Semi-Regular variable X Her. This envelope is partially resolved by the IRAM 30m telescope at 1mm and the line shapes appear narrower and more complex than most of the profiles observed towards AGB envelopes. We interpret the CO (1-0) and (2-1) profiles as resulting from three components in the wind : a very slowly expanding spherical component (v_exp=2.5 km/s) and two higher-velocity components (v_exp≥10km/s). These "high-velocity" components are symmetrically displaced compared to the slow component and are likely to be the red and blue shifted cones of a weakly collimated bipolar flow, probably seen with a small viewing angle (∼15deg). The bipolar flow contains between one fifth and one third of the total detected circumstellar gas mass of about 3x10^–4M_☉. The mass loss rate in the bipolar flow of about 1x10^–7M_☉/yr 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 evidence for asymmetries in or very near the stellar photosphere. The asymmetric flow may be especially conspicuous since the spherical portion of the mass loss has such a low velocity.