A STELLAR WIND BLOWN BUBBLE ASSOCIATED WITH THE WOLF-RAYET STAR HD-197406

A field of 2° sq. centered on the position HD 197406 (a spectroscopic binary composed of a WN7 star + unseen companion), has been surveyed in the H I 21 cm line and in the 1420 and 408 MHz radio continuum, using the synthesis radio telescope of the Dominion Radio Astrophysical Observatory (Canada). The spectral maps show the existence of a nearly complete ring-shaped H I shell (Rs ≅s 18 pc, νexp ≅ 6 km s-1, script M signet;H I ≅ 1200script M sign⊙) and, immersed within this shell, a small spherical bubble concentric with the star (Rb ≅4 pc, νexp ≅6 km s-1, script M signH I (missing) ≅ 8script M sign⊙). From these observations, a kinematical distance of 4.5 kpc is derived for HD 197406. At this distance, the binary has Mv≅ - 5.4 mag. The large H I shell is also detected at infrared wavelengths, as shown by the 60 and 100 μm IRAS images. We found neither thermal nor nonthermal radio sources associated with the binary system. Our observations suggest that the large shell has been created during previous evolutionary stages of the binary, while the small bubble has been recently blown by the WR wind.