The complex enviroment around Cir X-1

Abstract

We present the results of a 54 ks long Chandra observation of the peculiar source Cir X-1. We perform a comparative analysis of X-ray spectra, selected at different flux levels of the source. This allows us to distinguish between a very hard state, at a low countrate, and a brighter, softer, highly absorbed spectrum during episodes of flaring activity. The spectrum of the hard state clearly shows emission lines of highly ionized elements. During the flaring state, the spectrum also shows strong resonant absorption lines, mostly in the Fe K region. Physical implications on the changing system geometry and plasma behavior is discussed and compared with past observations.