Abstract
We analyzed the archival data of the X-ray pulsar Hercules X-1, observed with ASCA in 1994 August and 1996 April during the Main-High State of the 35-d cycle. The continuous spectrum in the energy range of 0.5–10 keV is found to have three components, i.e., power-law, soft blackbody, and highly absorbed power-law. In addition to the ∼ 6.5 keV iron K-shell line, we confirmed the existence of a broad emission feature around 1 keV that might be attributed to the iron L-shell lines. The line feature at ∼ 6.5 keV was resolved into two narrow lines at 6.4 keV and 6.7 keV from the ASCA/SIS spectrum. We performed a pulse-shape analysis in several energy bands and pulse phase-resolved spectroscopy, and found that a sinusoidal soft pulse consists of a blackbody and a broad ∼ 1 keV component, which is shifted by about 230° in phase from the pulse peak in the hard band which consists of a power-law and a highly absorbed power-law component. Assuming that the main beam, which is dominated by the power-law component, originates from the magnetic poles on the neutron star, we discuss the emission sites of other components in the context of an X-ray irradiated accretion disk.
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