Possible evidence for the existence of an H II region around the neutron star in LSI+65°010

Our spectroscopic observation of the Be/X-ray binary LSI+65°010 showed a dramatic variation in November 1992 with an increase by a factor of more than 3 in the equivalent width of the H_α emission line. This supports the view that the primary is a Be star rather than a supergiant. A well-defined double-peaked profile in seen in the spectrum of September 1994: while the red peak remained at 6563 Å, the blue one was −7.2Å to the blue. We suggest that such a profile is caused by the superposition of two emission lines, one from the shell of the Be star, one from an H II region around the neutron star. This provides, for the first time, direct observational evidence for the existence of a H II region around compact object and caused by X-ray emission. On 1992-11-04, the red side of the H_α line did not change while the blue side was greatly enhanced. We suggest that this may be caused by the H II region around the neutron star.