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

¹ Astrophysics Mission Division, Research and Scientific Support Department of ESA, ESTEC, Postbus 299, 2200 AG Noordwijk, The Netherlands e-mail: mdiaz@sciops.esa.int
² Department of Astronomy, University of Michigan, 500 Church Street, Dennison 814, Ann Arbor, MI 48109, USA
³ Integral Science Operations Centre, Science Operations and Data Systems Division, Research and Scientific Support Department of ESA, ESAC, Apartado 50727, 28080 Madrid, Spain
⁴ Laboratorio de Astrofísica Espacial y Física Fundamental, INTA, Apartado 50727, 28080 Madrid, Spain

Received: 11 April 2006
Accepted: 20 October 2006

Abstract

We report on two simultaneous XMM-Newton and INTEGRAL observations of the microquasar GRO J1655-40during 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 and in the EPIC pn spectra and blue-shifted ( ± 120 km s^-1) and features in the RGS spectra. The parameters of the photo-ionized absorber were different during the two observations with the ionization parameter, , decreasing from 3.60 ± 0.04 to 3.30 ± 0.04 erg cm s^-1and the column density decreasing from  10²² atom cm^-2to  10²² 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.