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The broad-band x ray spectral variability of Mkn 841The results of a detailed spectral analysis of four X-ray observations of the luminous Seyfert 1.5 galaxy Mkn 841 performed using the EXOSAT and Ginga satellites over the period June 1984 to July 1990 are reported. Preliminary results from a short ROSAT PSPC observation of Mkn 841 in July 1990 are also presented. Variability is apparent in both the soft (0.1-1.0 keV) and medium (1-20 keV) energy bands. Above 1 keV, the spectra are adequately modelled by a power-law with a strong emission line of equivalent width approximately 450 eV. The energy of the line (approximately 6.4 keV) is indicative of K-shell fluorescence from neutral iron, leading to the interpretation that the line arises via X-ray illumination of cold material surrounding the source. In addition to the flux variability, the continuum shape also changes in a dramatic fashion, with variations in the apparent photon index Delta(Gamma) approximately 0.6. The large equivalent width of the emission line clearly indicates a strongly enhanced reflection component in the source, compared to other Seyferts observed with Ginga. The spectral changes are interpreted in terms of a variable power-law continuum superimposed on a flatter reflection component. For one Ginga observation, the reflected flux appears to dominate the medium energy X-ray emission, resulting in an unusually flat slope (Gamma approximately 1.0). The soft X-ray excess is found to be highly variable by a factor approximately 10. These variations are not correlated with the hard flux, but it seems likely that the soft component arises via reprocessing of the hard X-rays. We find no evidence for intrinsic absorption, with the equivalent hydrogen column density constrained to be less than or equal to few x 10(exp 20) cm(exp -2). The implications of these results for physical models for the emission regions in this and other X-ray bright Seyferts are briefly discussed.
Document ID
19930009522
Acquisition Source
Legacy CDMS
Document Type
Other
Authors
George, I. M.
(Cambridge Univ. Cambridge, United Kingdom)
Nandra, K.
(Cambridge Univ. Cambridge, United Kingdom)
Fabian, A. C.
(Cambridge Univ. Cambridge, United Kingdom)
Turner, T. J.
(NASA Goddard Inst. for Space Studies New York, NY., United States)
Done, C.
(NASA Goddard Inst. for Space Studies New York, NY., United States)
Day, C. S. R.
(Tokyo Univ. Sagamihara, Japan)
Date Acquired
September 6, 2013
Publication Date
December 1, 1992
Publication Information
Publication: NASA. Goddard Space Flight Center, Goddard Visiting Scientist Program for the Space and Earth Sciences Directorate
Subject Category
Astronomy
Accession Number
93N18711
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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