Discovery of complex narrow X–ray absorption features from the low-mass X–ray binary GX 13+1 with XMM-Newton
Istituto di Fisica Cosmica “G. Occhialini", CNR, via Bassini 15, 20133 Milano, Italy
2 Astrophysics Division, Research and Scientific Support Department of ESA, ESTEC, Postbus 299, 2200 AG Noordwijk, The Netherlands
Corresponding author: L. Sidoli, email@example.com
Accepted: 31 January 2002
We report the detection of a complex of narrow X–ray absorption features from the low-mass X–ray binary GX 13+1 during 3 XMM-Newton observations in 2000 March and April. The features are consistent with being due to resonant scattering of the Kα and Kβ lines of He- and H-like iron (Fe xxv and Fe xxvi) and H-like calcium (Ca xx) Kα. Only the Fe xxvi Kα line has been previously observed from GX 13+1. Due to the closeness in energy the Fe xxv and Fe xxvi Kβ features may also be ascribed to Ni xxvii and Ni xxviii Kα, respectively. We also find evidence for the presence of a deep () Fe xxv absorption edge at 8.83 keV. The fits also require the presence of a broad emission feature whose energy and width are poorly determined, partly due to the presence of the deep Fe Kα features which severely cut into the feature and partly due to fit differences when using different XMM-Newton instruments. The equivalent widths of the lines do not show any obvious variation on a timescale of a few days suggesting that the absorbing material is a stable feature of the system and present during a range of orbital phases.
Key words: accretion, accretion disks / stars: individual: GX 13+1 / stars: neutron / X–rays: general
© ESO, 2002