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arXiv · 2505.07438

Traces of wobbling accretion disk in X-ray pulsar Her X-1 from observations of the ART-XC telescope of the SRG observatory

V. M. Revnivtsev·K. A. Postnov·S. V. Molkov·N. I. Shakura·A. Lutovinov·I. Yu. Lapshov·D. A. Kolesnikov·A. Yu. Tkachenko
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Abstract

Long uninterrupted observations of the X-ray binary system Her X-1 were performed with the Mikhail Pavlinsky ART-XC telescope of the Spectrum-Röntgen-Gamma (SRG) X-ray Observatory in the 4--25 keV energy range with a total exposure of about two days around the main turn-on of the X-ray source. We present the results of timing and spectral analysis of these observations. The opening of the X-ray source is determined to occur at the orbital phase $ϕ_{b}\approx 0.25$. The analysis of the X-ray light curve reveals a first direct observational evidence of the nutation of a tilted precessing accretion disk with a period of $\simeq0.87$ days. The appearance of X-ray pulsations near the orbital phase $ϕ_{b}\simeq 0.77$ prior to the main turn-on at the maximum of the nutation variability has been also detected. During the X-ray eclipse, a non-zero X-ray flux is measured, which is presumably associated with scattering of an X-ray emission in a hot corona around the optical star illuminated by the X-rays from the central neutron star. An increase in the X-ray flux after the main turn-on can be described by the passage of the radiation from the central source through a scattering corona above the precessing accretion disk.

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V. M. Revnivtsev, K. A. Postnov, S. V. Molkov, N. I. Shakura, A. Lutovinov, I. Yu. Lapshov, D. A. Kolesnikov, A. Yu. Tkachenko. 2025-05-12. Traces of wobbling accretion disk in X-ray pulsar Her X-1 from observations of the ART-XC telescope of the SRG observatory. https://arxiv.org/abs/2505.07438

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