The complex X-ray spectrum of the isolated neutron star RBS1223

We present a first analysis of a deep X-ray spectrum of the isolated neutron star RBS1223 obtained with XMM-Newton. Spectral data from four new monitoring observations in 2005/2006 were combined with archival observations obtained in 2003 and 2004 to form a spin-phase averaged spectrum containing 290 000 EPIC-pn photons. This spectrum shows higher complexity than its predecessors, and can be parameterised with two Gaussian absorption lines superimposed on a blackbody. The line centers, E-2 similar or equal to 2E(1), could be regarded as supporting the cyclotron interpretation of the absorption features in a field B similar to 4 x 10(13) G. The flux ratio of those lines does not support this interpretation. Hence, either feature might be of truly atomic origin.