Observations of 4U 1700-37 with BATSE

The eclipsing binary X-ray source 4U 1700-37 has been continually monitored by the BATSE experiment on the Compton Gamma Ray Observatory since the spring of 1991. Using source measurements at times of Earth occultation, we observe an average (uneclipsed) flux of 0.23 crab in the 20-120 keV band. The flux is highly variable, with occasional flaring behavior on timescales from hundreds of seconds to several hours and intensities as bright as 1 crab. The uneclipsed spectrum is well represented by an optically thin thermal bremsstrahlung model with a temperature of 25 keV independent of source intensity or orbital phase. An upper limit of 4% on the pulse fraction has been obtained for pulse periods between 2 and 700 s. Average orbital light curves from almost 1000 days of occultation measurements have been constructed. These profiles are used to measure (1) the eclipse semiangle, theta(E) = 28.degrees 6 +/- 2.degrees 1 in the 20-120 keV band, and (2) the decrease in orbital period, P over dot/P = -(3.3 +/- 0.6) x 10(-6) yr(-1). Estimates of system physical parameters are obtained using Monte Carlo simulations to propagate errors in measured and assumed parameters. For the X-ray source mass we find M(x) = 2.6(-1.4)(+2.3) M., and for the mass and radius of the optical companion, M(0) = 30(-7)(+11) M. and R(0) = 18(-2)(+2) R..