Spectral and temporal behavior of low mass X-ray binaries observed with the Einstein SSS and MPC, and the broadband X-ray telescope

An extensive survey of 50 low mass X-ray binaries was carried out using the HEAO-2 Einstein Solid State Spectrometer data (0.5-4.5 keV) with the Monitor Proportional Counter data (1.2-20.0 keV). The SSS provided 160 eV resolution below 4.5 keV with about 200 cm{dollar}sp2{dollar} of area, 100 times that of grating instruments on Einstein and EXOSAT. Additional observations were obtained with the Broad Band X-Ray Telescope (0.5-12 keV). Although LMXRB are some of the most luminous X-ray sources and include one of the first X-ray sources discovered, the nature of their emission regions has remained uncertain.; Spectra were selected on the basis of intensity and fit with a set of simple and complex spectral models. For all the subclasses, including Eddington-limited bulge sources, bursters, dippers, the soft spectrum black hole candidates, and a few transients in decline, the spectra could be fit acceptably with combinations of thermal bremsstrahlung and blackbody spectra or a Comptonized spectrum and a blackbody. The results rule out optically thick disk models for the bright Z sources and power law models for bursters. The results suggest a progression of spectra as a function of X-ray luminosity for the bursters, Atoll, and Z sources, in which there are separate emission regions, one optically thin to scattering. The optically thick component that appears for higher luminosity may be due to a boundary layer or to high optical depth to scattering in the flow. A lower temperature blackbody indicated in some cases could be an expected contribution from the accretion disk. The soft spectrum sources are dominated by blackbody spectra, but for two, low effective area of emission is a problem for the black hole interpretation. There did not appear to be any clear selection between models for the sources with high binary orbit inclinations.; Column densities for absorption by cold gas were determined simultaneously with the fits. They give distance estimates for the galactic bulge sources on the basis of a galactic disk model.; The strongest of previously reported low energy X-ray lines due to OVIII or Fe L transitions are confirmed. Similar line emission is seen for several other sources. The source X0614+091 exhibited a large emission feature consistent with being due to OVIII, showing that a low luminosity disk accretor can have a disk corona. For Cyg X-2 a broadened emission line centered on 6.7 keV was measured with BBXRT. It has been interpreted as K lines from Fe XXV emitted and scattered in the photoionized gas in the inner part of an accretion disk corona photoionized by the central X-ray source. Upper limits for line emission were obtained for X0614+091 and M15 which are consistent with the coronal model.