PROPERTIES OF THE MASSIVE X-RAY BINARY 4U-1700-37 = HD-153919

We re-examine the system parameters for the massive X-ray binary (MXRB) 4U 1700-37 in the light of modern spectroscopic theory and new ultraviolet and X-ray data. This system is composed of HD 153919, an O6f star having a stronger wind, and an accreting neutron star. In interpreting X-ray light curves for this system obtained from various X-ray experiments operating at different energies, we take into account the opacity of the wind to low-energy X-rays. Upon adopting the X-ray light curve from a high-energy experiment, OSO 8, we derive the following properties for the Of star: M(O) = 52 +/- 2 M., T(eff) = 42,000 K, log g = 3.6; a binary separation, a = 2.0 R(O); and a neutron-star mass, M(x) = 1.8 +/- 0.4 M.. These revised parameters for the Of component are in accord with the parameters of single Of stars, and hence, the problem that "the O star is undermassive by a factor of 2" (Conti 1978) is resolved. The revised value for the binary separation, a, results in improved parameters for the wind from the Of star: (1) the ratio of terminal velocity of the wind to photospheric escape velocity agrees with those of single 0 stars; (2) the discrepancy between the values of the wind acceleration parameter, beta, derived from X-ray and UV data is resolved; and (3) the acceleration of the wind is similar to that of single OB star winds. Finally, the revised system parameters aid in our understanding of the evolutionary history of the binary. We suggest that the supernova explosion producing the neutron star in 4U 1700-37 occurred over a million years ago when HD 153919 was still on the main sequence. The explosion nearly disrupted the system, leaving the stellar components in highly eccentric orbits. Since then, HD 153919 has evolved off the zero-age main sequence to become an O supergiant with an intense wind, which serves to power the X-ray emission.