Variable Quasi Periodic Oscillations during an outburst of the transient X-ray pulsar XTE J1858 + 034 |
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Authors: | U Mukherjee S Bapna H Raichur B Paul S N A Jaaffrey |
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Institution: | (1) Tata Institute of Fundamental Research, Homi Bhabha Road, Colaba, 400 005 Mumbai, India;(2) Department of Physics, College of Science, M. L. Sukhadia University, 313 001 Rajasthan, India;(3) Joint Astronomy Program, Indian Institute of Science, 560 012 Bangalore, India |
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Abstract: | We have investigated the Quasi Periodic Oscillation (QPO) properties of the transient accreting X-ray pulsar XTE J1858 + 034
during the second outburst of this source in April–May 2004. We have used observations made with the Proportional Counter
Array (PCA) of the Rossi X-ray Timing Explorer (RXTE) during May 14–18, 2004, in the declining phase of the outburst. We detected
the presence of low frequency QPOs in the frequency range of 140–185 mHz in all the RXTE-PCA observations. We report evolution
of the QPO parameters with the time, X-ray flux, and X-ray photon energy. Though a correlation between the QPO centroid frequency
and the instantaneous X-ray flux is not very clear from the data, we point out that the QPO frequency and the one day averaged
X-ray flux decreased with time during these observations. We have obtained a clear energy dependence of the RMS variation
in the QPOs, increasing from about 3% at 3 keV to 6% at 25 keV. The X-ray pulse profile is a single peaked sinusoidal, with
pulse fraction increasing from 20% at 3 keV to 45% at 30keV. We found that, similar to the previous outburst, the energy spectrum
is well fitted with a model consisting of a cut-off power law along with an iron emission line. |
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Keywords: | Stars: pulsar: individual (XTE J1858 + 034) X-rays: pulsar |
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