A relativistically smeared line profile in the spectrum of the bright Z-source GX 340+0

Abstract

We present preliminary results of a 50 ks long XMM-Newton observation of the bright Z-source GX 340+0. We study the temporal and spectral variability of the source, performing a time resolved analysis. In the energy spectra, a broad asymmetric emission line in the Fe Ka energy band is always present. Its shape is compatible with a relativistically smeared profile arising from reflection on a hot accretion disk extending close to the central accreting neutron star. Despite a significant change in the continuum emission and luminosity, the line profile remains substantially unchanged. The line is produced by recombination of highly ionized iron (Fe XXV), the reflecting disk has an inner radius close to 10 gravitational radii, while the fit requires a high value for the outer disk radius. The inclination of the source is well constrained at 35 deg, while the emissivity index is -2.33.