Detection of the faint companion in the massive binary HD 199579

We present new radial velocity data for the massive binary HD 199579 O6 V(( f)) based upon spectra obtained from IUE, the Canada-France-Hawaii Telescop e, KPNO, the David Dunlap Observatory, and the GSU Multiple-Telescope Teles cope. We derive a revised period, P = 48.5216 +/- 0.0015 days, and improved orbital elements that agree with the earlier elements within their errors. We applied a Doppler tomography algorithm to the KPNO spectra to reconstru ct the individual primary and secondary spectra in the red, yielding the fi rst detection of the secondary's spectrum. The spectral features observed, implied mass ratio (M-2/M-1 = 4 +/- 1), and magnitude difference (V-Delta = 2.5 +/- 0.3) are all consistent with a secondary of type B1 V-B2 V. The ma ximum angular separation of the components is predicted to be approximate t o1.2 mas, and thus the binary is an important target for optical interferom etry.