Optical identification of 4U1907+09 using the HEAO-1 scanning modulation collimator position

We report an optical identification of 4U1907+09 with a m/sub v/=16.4 stellar object in the location determined by the scanning modulation collimator experiment on the first High Energy Astronomy Observatory (HEAO-1). The identification is based on the presence of very strong and broad Hα emission. The optical data constrain the distance to be 2--13 kpc, and this gives a range of uncertainty to the typical 2--10 keV luminosity of (1 x 1035--3 x 1036) erg s-1. We report on the x-ray spectrum and variability. We apply the hypothesis that the object is an OB supergiant, although its faintness in the blue makes precise spectral classification impossible. We suggest that this system is an example of a luminous, massive primary emitting a stellar wind which is accreted on the compact object