Chandra grating spectroscopy of the X-ray binary 4U 1700-37 in a flaring state

Chandra X-Ray Observatory grating spectra of the supergiant X-ray binary 4U 1700-37 reveal emission lines from hydrogen- and helium-like S, Si, Mg, and Ne in the 4 - 13 Angstrom range. The spectrum also shows fluorescent lines from S and Si and a prominent Fe Kalpha line at 1.94 Angstrom. The lines contribute to the previously unaccounted "soft excess'' in the flux in this range at orbital phi approximate to 0.7. The X-ray source was observed during intermittent flaring, and the strengths of the lines vary with the source state. The widths of the lines (FWHM approximate to 1000 2000 km s(-1)) can result from either Compton scattering or Doppler shifts. Power spectra of the hard X- rays show red noise, and the soft X- rays and lines show in addition quasi-periodic oscillations and a power spectral break. Helium-like triplets of Si and Mg suggest that the gas is not in a pure photoionization equilibrium. We discuss whether resonant scattering could affect the line ratios or whether a portion of the wind may be heated to temperatures T similar to 10(6) K.