The Variable Iron Line in CYGNUS-X-3
van der Klis, M.; Manzo, G.; Smith, A.; Mason, K.; Peacock, A.; White, N.
Netherlands, Germany, United Kingdom, Italy
Abstract
Cygnus X-3 was observed with the GSPC on board EXOSAT on several occasions, one observation lasting for 7 orbital cycles. The width W and centroid energy E of the iron emission feature near 6.7 keV show a smooth, correlated, sinusoidal-type modulation, the iron line being widest and E being lowest just before X-ray maximum. The line profile may show a low-energy wing, but apart from this does not deviate strongly from a symmetric, Gaussian-type shape. The continuum at higher energies than the line is not completely smooth, but shows ‘bumps’ which remain stable in time. Two possible explanations are discussed for the correlated variation of E and W as a function of orbital phase.