Sachindra Naik1 and Biswajit Paul2
Abstract.
We present the results obtained from a study of the variability of iron emis-
sion lines in the high mass X-ray binary pulsar Cen X-3 during the eclipse, eclipse-
egress and out-of-eclipse phases using XMM − Newton observations. Three iron emis-
sion lines at 6.4 keV, 6.7 keV, and 6.97 keV are clearly detected in the spectrum of
the pulsar during the entire observations, irrespective of different binary phases. The
properties of these emission lines are investigated at different intensity levels. The flux
level and equivalent width of the emission lines change during the eclipse, eclipse-
egress and out-of-eclipse orbital phases. Based on the results obtained from the time
resolved spectral analysis, it is understood that the most probable emitting region of
6.4 keV fluorescent line is very close to the neutron star whereas the other two lines
are produced in a region that is far from the neutron star, probably in the highly photo-
ionized wind of the companion star or in the accretion disk corona.
Keywords: stars: binaries: general – stars: pulsars: general – stars: neutron – X-rays: binaries – X-rays: individual: Cen X-3
1Physical Research Laboratory, Navrangapura, Ahmedabad 380009, Gujarat, India
2Raman Research Institute, Sadashivnagar, C. V. Raman Avenue, Bangalore 560080, India