Orbital evolution and orbital phase resolved spectroscopy of the HMXB pulsar 4U 1538-52 with RXTE-PCA and BeppoSAX |
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Authors: | U Mukherjee H Raichur B Paul S Naik N Bhatt |
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Institution: | (1) Tata Institute of Fundamental Research, Homi Bhabha Road, Colaba, 400 005 Mumbai, India;(2) Joint Astronomy Program, Indian Institute of Science, 560 012 Bangalore, India;(3) Institute of Space and Astronautical Science, 3-1-1 Yoshinodai, Sagamihara, 229 8510 Kanagawa, Japan;(4) Nuclear Research Laboratory, Bhabha Atomic Research Centre, 400 085 Mumbai, India |
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Abstract: | We report here results from detailed timing and spectral studies of the high mass X-ray binary pulsar 4U 1538-52 over several
binary periods using observations made with the Rossi X-ray Timing Explorer (RXTE) and BeppoSAX satellites. Pulse timing analysis
with the 2003 RXTE data over two binary orbits confirms an eccentric orbit of the system. Combining the orbitial parameters
determined from this observation with the earlier measurements we did not find any evidence of orbital decay in this X-ray
binary. We have carried out orbital phase resolved spectroscopy to measure changes in the spectral parameters with orbital
phase, particularly the absorption column density and the iron line flux. The RXTE-PCA spectra in the 3–20 keV energy range
were fitted ∼6.4 keV, whereas the BeppoSAX spectra needed only a power law and Gaussian emission line at ∼6.4 keV in the restricted
energy range of 0.3–10.0 keV. An absorption along the line of sight was included for both the RXTE and BeppoSAX data. The
variation of the free spectral parameters over the binary orbit was investigated and we found that the variation of the column
density of absorbing material in the line of sight with orbital phase is in reasonable agreement with a simple model of a
spherically symmetric stellar wind from the companion star. |
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Keywords: | Stars: binaries: eclipsing stars: pulsars: individual:4U 1538-52 X-rays: stars |
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