Disk reflection signatures in the spectrum of the bright z-source gx340+0

Abstract

We present the preliminary results of a 50 ks long XMM-Newtonobservation of the bright Z-source GX 340+0. In this Letter, we focuson the study of a broad asymmetric emission line in the Fe K alphaenergy band, whose shape is clearly resolved and compatible with arelativistically smeared profile arising from reflection on a hotaccretion disk extending close to the central accreting neutron star.By combining temporal and spectral analysis, we are able to follow theevolution of the source along its horizontal branch. However, despite asignificant change in the continuum emission and luminosity, the lineprofile does not show any strong correlated variation. This broad lineis produced by recombination of highly ionized iron ( Fe xxv) at aninferred inner radius close to 13R(g), while the fit requires a highvalue for the outer disk radius. The inclination of the source isextremely well constrained at 35 degrees, while the emissivity index is-2.50.