EXTREME ULTRAVIOLET EXPLORER OBSERVATIONS OF HERCULES X-1 OVER A 35 DAY CYCLE
- Department of Physics, University of Calgary, Calgary, Alberta, T2N 1N4 (Canada)
- Space Astronomy, Canadian Space Agency, John H. Chapman Space Centre, 6767 Route de l'Aeroport Saint-Hubert, Quebec J3Y 8Y9 (Canada)
Observations of Hercules X-1 by the Extreme Ultraviolet Explorer covering most of the 35 day cycle are reported here. This is the only long extreme ultraviolet (EUV) observation of Her X-1. Simultaneous X-ray observations with the Rossi X-ray Timing Explorer All-Sky Monitor (RXTE/ASM) X-ray show that Her X-1 is in an X-ray anomalous low state. The first 4 days are also observed with the RXTE proportional counter array (PCA), which shows that the X-ray properties are nearly the same as for normal low states in Her X-1 with flux reduced by a factor of 2. In contrast, the EUV emission from Her X-1 is reduced by a factor of {approx}4 compared to normal low states. The twisted-tilted accretion disk responsible for the normal 35 day X-ray cycle can be modified to explain this behavior. An increased disk twist reduces the X-ray illumination of HZ Her by a factor of {approx}2 and of the disk surface by a somewhat larger factor, leading to a larger reduction in EUV flux compared to X-ray flux.
- OSTI ID:
- 21450947
- Journal Information:
- Astrophysical Journal, Vol. 715, Issue 2; Other Information: DOI: 10.1088/0004-637X/715/2/897; ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
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COSMOLOGY AND ASTRONOMY
ACCRETION DISKS
EMISSION
EXTREME ULTRAVIOLET RADIATION
ILLUMINANCE
NEUTRONS
POLAR-CAP ABSORPTION
PROPORTIONAL COUNTERS
STARS
X RADIATION
ABSORPTION
BARYONS
ELECTROMAGNETIC RADIATION
ELEMENTARY PARTICLES
FERMIONS
HADRONS
IONIZING RADIATIONS
MEASURING INSTRUMENTS
NUCLEONS
RADIATION DETECTORS
RADIATIONS
SORPTION
ULTRAVIOLET RADIATION