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XMM-Newton EPIC and OM Observations of Her X-1 over the 35 d Beat Period and an Anomalous Low State

S. Zane·G. Ramsay·M. A. Jimenez-Garate·J. W. den Herder·M. Still·P. T. Boyd·C. J. Hailey
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Abstract

We present the results of a series of XMM-Newton EPIC and OM observations of Her X-1, spread over a wide range of the 35 d precession period. We confirm that the spin modulation of the neutron star is weak or absent in the low state - in marked contrast to the main or short-on states. The strong fluorescence emission line at ~6.4 keV is detected in all observations (apart from one taken in the middle of eclipse), with higher line energy, width and normalisation during the main-on state. In addition, we report the detection of a second line near 7 keV in 10 of the 15 observations taken during the low-intensity states of the system. We discuss these observations in the context of previous observations, investigate the origin of the soft and hard X-rays and consider the emission site of the 6.4keV and 7keV emission lines.

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S. Zane, G. Ramsay, M. A. Jimenez-Garate, J. W. den Herder, M. Still, P. T. Boyd, C. J. Hailey. 2005-03-10. XMM-Newton EPIC and OM Observations of Her X-1 over the 35 d Beat Period and an Anomalous Low State. https://doi.org/10.1063/1.2130274

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