Correlated multiwavelength emission from the X-ray-bright Seyfert galaxy III Zw 2 |
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| Authors: | N. J. Salvi,M. J. Page,J. A. Stevens,,K. Wu,K. O. Mason,M. F. Aller,H. D. Aller,H. Terä sranta,E. Romero-Colmenero,F. A. Cordova, W. C. Priedhorsky |
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| Affiliation: | Mullard Space Science Laboratory, University College London, Holmbury St Mary, Dorking, Surrey RH5 6NT;Astronomy Technology Centre, Royal Observatory, Blackford Hill, Edinburgh EH9 3HJ;Astronomy Department, University of Michigan, Ann Arbour, MI 48109-1090, USA;Metsähovi Radio Observatory, Metsähovintie, FIN-02540 Kylmälä, Finland;South African Astronomical Observatory, PO Box 9, Observatory 7935, South Africa;Department of Physics, University of California, Santa Barbara, CA 93106, USA;NIS Division, Los Alamos National Laboratory, Los Alamos, NM 87545, USA |
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| Abstract: | The X-ray-bright Seyfert 1 galaxy III Zw 2 was observed with XMM–Newton in 2000 July. Its X-ray spectrum can be described by a power law of photon index Γ= 1.7 and an extremely broad (FWHM∼ 140 000 km s−1 ) Fe Kα line at 6.44 keV. The iron line has an equivalent width of ∼800 eV. To study the long-term X-ray behaviour of the source we have analysed 25 yr of data, from 1975 to 2000. There is no evidence of significant intrinsic absorption within the source or of a soft X-ray excess in the XMM or archival data. We do not detect rapid X-ray variability (a few × 103 s ) during any of the individual observations; however, on longer time-scales (a few years) the X-ray light curve shows 10-fold flux variations. We infer a black hole mass of ∼109 M⊙ (from Hβ FWHM) for III Zw 2 which is much higher than some previous estimates.
A comparison of X-ray variability with light curves at other wavelengths over a 25-yr period reveals correlated flux variations from radio to X-ray wavelengths. We interpret the variable radio to optical emission as synchrotron radiation, self-absorbed in the radio/millimetre region, and the X-rays mainly as a result of Compton up-scattering of low-energy photons by the population of high-energy electrons that give rise to the synchrotron radiation. |
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| Keywords: | accretion accretion discs galaxies: active galaxies: nuclei quasars: general quasars: individual: III Zw 2 |
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