A large HI shell surrounding the Wolf-Rayet star HD 191765

We have surveyed a 2.degrees 6 x 2.degrees 6 field centered on the Wolf-Ray et (W-R) star HD 191765 (=WR 134) in the H I 21 cm line and in the 1420 and 408 MHz radio continuum, using the Synthesis Telescope of the Dominion Rad io Astrophysical Observatory, to search for direct evidence of the interact ion between the W-R star wind and the interstellar medium. An are-shaped st ructure is present in the 1420 MHz continuum image, which perfectly matches the optical nebula Anon (MR 100). That this gas is not visible on our 408 MHz map hints at the thermal nature of the source. This ionized gas could b e associated with luminous blue variable or red supergiant ejecta swept up by the W-R wind and photoionized by the strong ultraviolet flux from the st ar. However, this suggestion needs to be confirmed by clear CNO enrichment measurements in the northwest region of the nebula. Our H I maps reveal the existence of a nearly complete shell at a velocity of v(sys) = -11.44 km s(-1) (R-s approximate to 20.9 pc, v(exp) approximate to 9.9 km s(-1), M-H I approximate to 1830 M-.), which, mainly for morphol ogical reasons, we associate with HD 191765 (although a contribution from t he nearby W-R star HD 192103 cannot be totally excluded). The dynamical age of this bubble (similar to 1.3 x 10(6) yr) suggests that it was mainly blo wn during the main-sequence progenitor O-star phase. The kinematic distance corresponding to a local standard of rest velocity of -11 km s(-1) is appr oximately 5 kpc, which is incompatible with the association distance of HD 191765 of 2.1 kpc. Therefore, we conclude that the H I bubble we have detec ted was blown in gas already in movement with respect to normal Galactic ro tation for this region. There is independent evidence that gas at this velo city is present in this line of sight. Recent Hipparcos data analyzed by Mo ffat et al. give a supersonic proper motion for HD 191765 (projected veloci ty similar to 52 km s(-1) at a position angle on the sky of P.A. = -38 degr ees). This velocity vector points away from a position very close to the ce nter of the H I bubble, which strengthens the hypothesis of a physical link with the W-R star. The supersonic velocity of the star with respect to the interstellar medium might have generated some compression of the interstel lar medium in the southwest region, rendering the Ha gas brighter in that d irection with respect to the surroundings.