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arXiv · astro-ph/9707042

BeppoSAX observation of the X-ray binary pulsar Vela X-1

M. Orlandini·D. Dal Fiume·L. Nicastro·S. Giarrusso·A. Segreto·S. Piraino·G. Cusumano·S. Del Sordo·M. Guainazzi·L. Piro
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Abstract

We report on the spectral (pulse averaged) and timing analysis of the ~ 20 ksec observation of the X-ray binary pulsar Vela X-1 performed during the BeppoSAX Science Verification Phase. The source was observed in two different intensity states: the low state is probably due to an erratic intensity dip and shows a decrease of a factor ~ 2 in intensity, and a factor 10 in Nh. We have not been able to fit the 2-100 keV continuum spectrum with the standard (for an X--ray pulsar) power law modified by a high energy cutoff because of the flattening of the spectrum in ~ 10-30 keV. The timing analysis confirms previous results: the pulse profile changes from a five-peak structure for energies less than 15 keV, to a simpler two-peak shape at higher energies. The Fourier analysis shows a very complex harmonic component: up to 23 harmonics are clearly visible in the power spectrum, with a dominant first harmonic for low energy data, and a second one as the more prominent for energies greater than 15 keV. The aperiodic component in the Vela X-1 power spectrum presents a knee at about 1 Hz. The pulse period, corrected for binary motion, is 283.206 +/- 0.001 sec.

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M. Orlandini, D. Dal Fiume, L. Nicastro, S. Giarrusso, A. Segreto, S. Piraino, G. Cusumano, S. Del Sordo, M. Guainazzi, L. Piro. 1997-07-03. BeppoSAX observation of the X-ray binary pulsar Vela X-1. https://doi.org/10.1063/1.53978

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