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arXiv · 2106.14261

Pulsating iron spectral features in the emission of X-ray pulsar V0332+53

S. D. Bykov·E. V. Filippova·M. R. Gilfanov·S. S. Tsygankov·A. A. Lutovinov·S. V. Molkov
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Abstract

We present results of phase- and time-resolved study of iron spectral features in the emission of the Be/X-ray transient pulsar V0332+53, during its type II outburst in 2004 using archival RXTE/PCA data. Coherent pulsations of both fluorescent iron line at {\approx}6.4 keV and neutral iron K-edge at {\approx}7.1 keV have been detected throughout the entire outburst. The pulsating iron K-edge is reported for the first time for this object. Near the peak of the outburst, the 3-12 keV pulse profile shows two deep, F_max / F_min ~ 2, and narrow dips of nearly identical shape, separated by exactly {\Delta}{\phi}=0.5 in phase. The dip spectra are nearly identical to each other and very similar in shape to the spectra outside the dips. The iron K-edge peaks at the phase intervals corresponding to the dips, although its optical depth {\tau}_K ~ 0.05 is by far insufficient to explain the dips. The iron line shows pulsations with a complex pulse profile without any obvious correlation with the total flux or optical depth of the K-edge. Accounting for the component associated with reprocessing of the pulsar emission by the surface of the donor star and circumstellar material, we find a very high pulsation amplitude of the iron line flux, F_max / F_min ~ 10. We demonstrate that these properties of V0332+53 can not be explained by contemporary emission models for accreting X-ray pulsars and speculate about the origin of the observed iron spectral features.

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S. D. Bykov, E. V. Filippova, M. R. Gilfanov, S. S. Tsygankov, A. A. Lutovinov, S. V. Molkov. 2021-06-27. Pulsating iron spectral features in the emission of X-ray pulsar V0332+53. https://doi.org/10.1093/mnras/stab1852

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