INTEGRAL and RXTE Observations of Centaurus A

Rothschild, Richard E. ; /San Diego, CASS ; Wilms, Joern ; U., /Warwick ; Tomsick, John ; /San Diego, CASS ; Staubert, Ruediger ; Benlloch, Sara ; /Tubingen U., IAAT ; Collmar, Werner /Garching, Max Planck Inst., MPE ; Madejski, Grzegorz ; /SLAC ; Deluit, Sandrine ; /Toulouse, CESR ; Khandrika, Harish ; School, /La Jolla High

Stanford Linear Accelerator Center

关键词: Calibration;    Origin;    Geometry;    Astrophysics,Astro;    Accretion Disks;   

DOI  :  10.2172/878001
RP-ID  :  SLAC-PUB-11631
RP-ID  :  AC02-76SF00515
RP-ID  :  878001

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来源: UNT Digital Library

【 摘 要 】

INTEGRAL and RXTE performed three simultaneous observations of the nearby radio galaxy Centaurus A in 2003 March, 2004 January, and 2004 February with the goals of investigating the geometry and emission processes via the spectral/temporal variability of the X-ray/low energy gamma ray flux, and intercalibration of the INTEGRAL instruments with respect to those on RXTE. Cen A was detected by both sets of instruments from 3-240 keV. When combined with earlier archival RXTE results, we find the power law continuum flux and the line-of-sight column depth varied independently by 60% between 2000 January and 2003 March. Including the three archival RXTE observations, the iron line flux was essentially unchanging, and from this we conclude that the iron line emitting material is distant from the site of the continuum emission, and that the origin of the iron line flux is still an open question. Taking X-ray spectral measurements from satellite missions since 1970 into account, we discover a variability in the column depth between 1.0 x 10{sup 23} cm{sup -2} and 1.5 x 10{sup 23} cm{sup -2} separated by approximately 20 years, and suggest that variations in the edge of a warped accretion disk viewed nearly edge-on might be the cause. The INTEGRAL OSA 4.2 calibration of JEM-X, ISGRI, and SPI yields power law indices consistent with the RXTE PCA and HEXTE values, but the indices derived from ISGRI alone are about 0.2 greater. Significant systematics are the limiting factor for INTEGRAL spectral parameter determination.