Journal
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
Volume 343, Issue 1, Pages L1-L4Publisher
BLACKWELL PUBLISHING LTD
DOI: 10.1046/j.1365-8711.2003.06783.x
Keywords
galaxies : active; galaxies : individual : Circinus galaxy; X-rays : galaxies
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We discuss the iron and nickel properties in the nuclear X-ray-reflecting region of the Circinus galaxy, studied with XMM-Newton . The main results are as follows. (i) From the depth of the Fe Kalpha edge, a value of A(Fe)=1.7 in number with respect to the cosmic value (as for Anders & Grevesse) is measured, if the (not directly visible) illuminating spectrum is assumed to be that measured by BeppoSAX . If the slope of the primary power law is left free to vary, a steeper spectrum and a lower iron abundance (about 1.2) are found. (ii) From the Ni to Fe Kalpha line flux ratio, a nickel-to-iron abundance ratio of 0.055-0.075 is found. (iii) The Fe Kbeta/Kalpha flux ratio is slightly lower than expected, possibly due to a mild ionization of iron (which, however, cannot be much more ionized than x). (iv) The presence of the Fe Kalpha Compton shoulder, already discovered by Chandra , is confirmed, its relative flux implying Compton-thick matter. This further supports the identification of the reflecting region with the absorber.
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