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Hercules X-1: Spectral Variability of an X-Ray Pulsar in a Stellar Binary SystemA cosmic X-ray spectroscopy experiment onboard the Orbiting Solar Observatory 8 (OSO-8), observed Her x-1 continuously for approximately 8 days. Spectral-temporal correlations of the X-ray emission were obtained. The major results concern observations of: (1) iron band emission, (2) spectral hardening (increase in effective x-ray temperature) within the X-ray pulse, and (3) a transition from an X-ray low state to a high state. The spectrum obtained prior to the high state can be interpreted as reflected emission from a hot coronal gas surrounding an accretion disk, which itself shields the primary X-ray source from the line of sight during the low state. The spectral hardening within the X-ray pulse was indicative of the beaming mechanism at the neutron star surface. The hardest spectrum by pulse phase was identified with the line of sight close to the Her x-1 magnetic dipole axis, and the X-ray pencil beam become harder with decreasing angle between the line of sight and the dipole axis.
Document ID
19770008019
Acquisition Source
Legacy CDMS
Document Type
Thesis/Dissertation
Authors
Pravdo, S. H. (NASA Goddard Space Flight Center Greenbelt, MD, United States)
Date Acquired
September 3, 2013
Publication Date
December 1, 1976
Subject Category
Astronomy
Report/Patent Number
NASA-TM-X-71247
X-661-76-280
Accession Number
77N14962
Funding Number(s)
CONTRACT_GRANT: NGR-21-002-316
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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