Discovery of iron-K absorption lines from the transient jets GRS 1915+105 and GRO J1655-40 Original Research Article

K-line absorption features of highly ionized iron were discovered in X-ray spectra of super-luminal transient jets GRS 1915+105 and GRO J1655-40 with ASCA. The absorption lines were identified as Fexxv Kα, Fexxvi Kα, and Nixxvii Kα resonance lines with equivalent width of 20–50 eV. They are evidence of highly ionized plasma in anisotropic configuration or in anisotropic illumination in the vicinity of the source. We adopted models of photoionized plasma with a cylindrical geometry, and estimated physical parameters such as density, dimension, solid angle from the source, temperature and ξ;-parameter. It is suggested that the kinetic temperature of resonant scattering atoms is very high, at least 100 keV.