Temporal and spectral studies of Hercules X-1 with ASCA Original Research Article

We observed the X-ray pulsar Hercules X-1 with ASCA in August 1994 during the Main-On phase of the 35-d cycle. The continuum spectrum in the 0.5 10 keV range is found to have three components; a power-law, a soft blackbody, and a highly absorbed power-law component. We confirmed the existence of a broad emission line feature around 1 keV that might be attributed to the iron L-shell lines. The iron Kα-line feature was resolved into two narrow lines at 6.4 keV and 6.7 keV from the ASCA/SIS spectrum. We performed pulse-shape analysis in several energy-bands and found that the sinusoidal pulse component consists of the blackbody and the broad ∼ 1 keV line and the iron line, and the sharppeak component with a shoulder consists of the power-law. The peak of the sinusoidal pulse is about 230° shifted in phase from that of the main pulse.