Rodes Roca, José Joaquín, Page, Kim L., Torrejon, Jose M., Osborne, Julian P., Bernabeu, Guillermo
Detecting emission lines with XMM-Newton in 4U 1538–52
Astronomy & Astrophysics. 2011, 526: A64. doi:10.1051/0004-6361/201014324
URI: http://hdl.handle.net/10045/89569
DOI: 10.1051/0004-6361/201014324
ISSN: 0004-6361 (Print)
Abstract: 
Context. The properties of the X-ray emission lines are a fundamental tool for studying the nature of the matter surrounding the neutron star and the phenomena that produce these lines. Aims. The aim of this work is to analyse the X-ray spectrum of 4U 1538−52 obtained by the XMM-Newton observatory and to look for the presence of diagnostic lines in the energy range 0.3−11.5 keV. Methods. We used a 54 ks PN & MOS/XMM-Newton observation of the high-mass X-ray binary 4U 1538−52 covering the orbital phase between 0.75 to 1.00 (the eclipse ingress). We modelled the 0.3−11.5 keV continuum emission with three absorbed power laws and looked for the emission lines. Results. We found previously unreported recombination lines in this system at  ~2.4 keV,  ~1.9 keV, and  ~1.3 keV, which is consistent with the presence of highly ionized states of S XV Heα, Si XIII Heα, and either Mg Kα or Mg XI Heα. On the other hand, in spectra that are both out of eclipse and in eclipse, we detect a fluorescence iron emission line at 6.4 keV, which is resolved into two components: a narrow (σ ≤ 10 eV) fluorescence Fe Kα line plus one hot line from highly photoionized Fe XXV. Conclusions. The detection of new recombination lines during eclipse ingress in 4U 1538−52 indicates that there is an extended ionized region surrounding the neutron star.
Keywords:X-rays: binaries, Pulsars: individual: 4U 1538−52
EDP Sciences
info:eu-repo/semantics/article