RESOLVING THE CYGNUS-X-3 IRON K-LINE

An ASCA observation of Cygnus X-3 on 1993 June 11, in its X-ray high i ntensity state, has for the first time resolved the broad iron K line emission into three components: a He-like line at 6.67 +/- 0.01 keV, a H-like line at.6.96 +/- 0.02 keV, and a neutral line at 6.37 +/- 0.03 keV. The line intensities of the 6.67 keV and 6.96 keV lines are modu lated with the 4.8 hr orbital period and are maximum when the continuu m intensity is minimum. There is a sharp minimum of the line intensity on the rising phase of the continuum intensity. An iron absorption ed ge is observed at 7.19 +/- 0.02 keV. The optical depth of the absorpti on edge varies from 0.3 to 0.5 and is in anti-phase with the overall X -ray continuum modulation. The observed complexity of the iron K line region is greater than that had been assumed in previous spectral mode lling based on observations with lower resolution detectors.