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Scott, D.M. and Leahy, D.A. (1999) Rossi X-Ray Timing Explorer All-Sky Monitor Observations of the 35 Day Cycle of Hercules X-1. The Astrophysical Journal, 510, 974-985.
https://doi.org/10.1086/306631

has been cited by the following article:

• TITLE: Spectral Evolution of Hercules X-1 over Main High State from RXTE/PCA Observations

  AUTHORS: Denis A. Leahy, Mohammed H. Abdallah

  KEYWORDS: X-Ray Binaries, Hercules X-1, X-Ray Spectrum

  JOURNAL NAME: Journal of High Energy Physics, Gravitation and Cosmology, Vol.8 No.4, August 31, 2022

  ABSTRACT: We test different X-ray spectrum models to find the one that best represents the observed Rossi X-ray Timing Explore/Proportional Counter Array (RXTE/ PCA) spectra of Her X-1 during Main High state (MH). We then apply this model to MH observations taken over the lifetime of RXTE. From the results, we obtain patterns in the spectral parameters vs. 35-day phase during MH. The precessing-disc occultation model explains the 35-day cycle by changes in observer view of the emission regions by the accretion disc 35-day precession. Qualitatively, we find that this model can describe the main spectral changes. However, several spectral parameters show detailed changes that the models have not addressed yet. These changes will likely require modifications to the basic precessing-disc model for the 35-day cycle.