[ITAL]Rossi X-Ray Timing Explorer[/ITAL] Observation of Cygnus X-1 in Its High State
- 1 January 1997
- journal article
- research article
- Published by American Astronomical Society in The Astrophysical Journal
- Vol. 474 (1) , L57-L60
- https://doi.org/10.1086/310419
Abstract
We present the results from the Rossi X-Ray Timing Explorer observations of Cygnus X-1 in its high state. In the energy range of 2-200 keV, the observed X-ray spectrum can be described by a model consisting of a soft blackbody component and a broken power law with a high-energy cutoff. The low-energy spectrum (below ~11 keV) varies significantly from observation to observation while the high-energy portion changes little. The X-ray flux varies on all timescales down to milliseconds. The power density spectrum (PDS) can be characterized by excess red noise ("1/f") at low frequencies and a white-noise component that extends to 1-3 Hz before being cut off. At higher frequencies, the PDS becomes power-law again, with a slope of roughly -2 (i.e., "1/f2"). Broad peaks in the range of 3-9 Hz are present and might be due to quasi-periodic oscillations. The PDS shows interesting spectral dependence: the 1/f component becomes more prominent when the low-energy spectrum becomes softer. The difference in the observed spectral and timing properties between the low and high states is qualitatively consistent with a simple "fluctuating corona" model.Keywords
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This publication has 9 references indexed in Scilit:
- An Intermediate State of Cygnus X-1The Astrophysical Journal, 1996
- First Results from the All-Sky Monitor on the [ITAL]Rossi X-Ray Timing Explorer[/ITAL]The Astrophysical Journal, 1996
- Quasi-periodic X-Ray Brightness Oscillations of GRO J1744−28The Astrophysical Journal, 1996
- ASCA Observations of the Iron Line Structure in Cygnus X-1The Astrophysical Journal, 1996
- High-Energy Spectral Complexity from Thermal Gradients in Black Hole AtmospheresThe Astrophysical Journal, 1995
- Is a black hole accretion disk in a self-organized critical state?The Astrophysical Journal, 1994
- Another canonical time variation of X-rays from black hole candidates in the very high flare state?The Astrophysical Journal, 1993
- Long-term gamma-ray spectral variability of Cygnus X-1The Astrophysical Journal, 1987
- Intensity transitions in Cyg XR-1 observed at high energies from OSO 8Nature, 1977