Rothschild, Richard E., 1943-, Wilms, J. (Joern), Tomsick, J., Staubert, R., Benlloch, S., Collmar, Werner, Madejski, G. M., Deluit, Sandrine and Khandrika, Harish. (2006) Integral and RXTE observations of Centaurus A. Astrophysical Journal, Vol.641 (No.2 Part 1). pp. 801-821. ISSN 0004-637X

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Abstract

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 to 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(23) and 1.5 x 10(23) cm(-2) separated by approximately 20 yr, 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.

Item Type:	Journal Article
Subjects:	Q Science > QB Astronomy
Divisions:	Faculty of Science > Physics
Journal or Publication Title:	Astrophysical Journal
Publisher:	Institute of Physics Publishing, Inc.
ISSN:	0004-637X
Date:	20 April 2006
Volume:	Vol.641
Number:	No.2 Part 1
Number of Pages:	21
Page Range:	pp. 801-821
Identification Number:	10.1086/500534
Status:	Peer Reviewed
Publication Status:	Published
Access rights to Published version:	Open Access
Funder:	National Science Foundation (U.S.) (NSF)
Grant number:	NSF_INT-9815741, NSF_INT-0003773
URI:	http://wrap.warwick.ac.uk/id/eprint/33684

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