XMM-Newton and INTEGRAL spectroscopy of the microquasar GRO J1655-40 during its 2005 outburst

Abstract

We report on two simultaneous XMM-Newton and INTEGRAL observations of the microquasar GRO J1655-40 during the 2005 outburst when the source was in its high-soft state. The 0.3-200 keV spectra are complex with an overall continuum which may be modeled using an absorbed blackbody together with a weak, steep, power-law component. In addition, there is evidence for the presence of both a relativistically broadened Fe K line and a highly photo-ionized absorber. The photo-ionized absorber is responsible for strong K absorption lines of Fe XXV and Fe XXVI in the EPIC pn spectra and blue-shifted (v = -540 +/- 120 km/s) Ne X and Fe XXIV features in the RGS spectra. The parameters of the photo-ionized absorber were different during the two observations with the ionization parameter, logxi, decreasing from 3.60 +/- 0.04 to 3.30 +/- 0.04 erg cm/s and the column density decreasing from (5.2 +/- 1.0) x 10^22 atom cm-2 to (1.5 +/- 1.0) x 10^22 atom cm-2 during the first and second observations as the 0.5-200 keV GRO J1655-40 luminosity decreased by around a half. At 90% confidence the INTEGRAL data show no evidence of a break in the power-law component up to energies of 380 keV and 90 keV for the first and second observations, respectively.