Narrow absorption features in the co-added XMM-Newton RGS spectra of isolated neutron stars

We co-added the available XMMNewton Reflection Grating Spectrometer (RGS) spectra for each of the isolated X-ray pulsars RX J0720.4-3125, RX J1308.6+2127 (RBS1223), RX J1605.3+3249 and RX J1856.4-3754 (four members of the Magnificent Seven) and the Three Musketeers Geminga, PSR B0656+14 and PSR B1055-52. We confirm the detection of a narrow absorption feature at 0.57 keV in the co-added RGS spectra of RX J0720.4-3125 and RX J1605.3+3249 (including most recent observations). In addition, we found similar absorption features in the spectra of RX J1308.6+2127 (at 0.53 keV) and maybe PSR B1055-52 (at 0.56 keV). The absorption feature in the spectra of RX J1308.6+2127 is broader than the feature e.g. in RX J0720.4-3125. The narrow absorption features are detected with 25.6s significance.