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arXiv · 1410.4563

NuSTAR observations and broadband spectral energy distribution modeling of the millisecond pulsar binary PSR J1023+0038

K. L. Li·A. K. H. Kong·J. Takata·K. S. Cheng·P. H. T. Tam·C. Y. Hui·Ruolan Jin
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Abstract

We report the first hard X-ray (3-79 keV) observations of the millisecond pulsar (MSP) binary PSR J1023+0038 using NuSTAR. This system has been shown transiting between a low-mass X-ray binary (LMXB) state and a rotation-powered MSP state. The NuSTAR observations were taken in both LMXB state and rotation-powered state. The source is clearly seen in both states up to ~79 keV. During the LMXB state, the 3-79 keV flux is about a factor of 10 higher that in the rotation-powered state. The hard X-rays show clear orbital modulation during the X-ray faint rotation-powered state but the X-ray orbital period is not detected in the X-ray bright LMXB state. In addition, the X-ray spectrum changes from a flat power-law spectrum during the rotation-powered state to a steeper power-law spectrum in the LMXB state. We suggest that the hard X-rays are due to the intra-binary shock from the interaction between the pulsar wind and the injected material from the low-mass companion star. During the rotation-powered MSP state, the X-ray orbital modulation is due to Doppler boosting of the shocked pulsar wind. At the LMXB state, the evaporating matter of the accretion disk due to the gamma-ray irradiation from the pulsar stops almost all the pulsar wind, resulting the disappearance of the X-ray orbital modulation.

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K. L. Li, A. K. H. Kong, J. Takata, K. S. Cheng, P. H. T. Tam, C. Y. Hui, Ruolan Jin. 2014-10-16. NuSTAR observations and broadband spectral energy distribution modeling of the millisecond pulsar binary PSR J1023+0038. https://doi.org/10.1088/0004-637x/797/2/111

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