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    Please use this identifier to cite or link to this item: http://ir.lib.ncu.edu.tw/handle/987654321/39252


    Title: SOFT-X-RAY AND ULTRAVIOLET OBSERVATIONS OF MRK-841 - IMPLICATIONS FOR THE BLUE BUMP
    Authors: NANDRA,K;TURNER,TJ;GEORGE,IM;FABIAN,AC;SHRADER,C;SUN,WH
    Contributors: 物理研究所
    Keywords: ACTIVE GALACTIC NUCLEI;ACCRETION DISKS;SEYFERT-GALAXIES;COLD MATTER;QUASARS;NGC-5548;SPECTRA;VARIABILITY;CONTINUUM;EMISSION
    Date: 1995
    Issue Date: 2010-07-08 14:09:49 (UTC+8)
    Publisher: 中央大學
    Abstract: We present an analysis of an extended ROSAT observation of the Seyfert galaxy Mrk 841. The source is clearly variable on short time-scales with distinctive changes in the hardness ratio, indicating that more than one spectral component is present in the PSPC band. Spectral modelling of the soft X-ray data confirms this complex picture. The data show that the continuum is particularly steep in the soft band (Gamma=2.4). We find that the soft X-ray spectrum is best fitted by models in which the primary power law is modified either by absorption by highly ionized material in the line of sight, or by an additional emission component which contributes to the lowest PSPC channels. Simultaneous spectral fitting of the PSPC data and the UV continuum data, which were obtained contemporaneously with IUE, show that the best-fitting power law in the soft X-ray extrapolates well into the UV and carries the bulk of the source power. We have been unable to find a satisfactory fit to the UV/soft X-ray emission with standard accretion disc models. One possibility is that the disc spectrum is modified substantially by Comptonization in a corona above the disc. Future variability data should allow us to test this model.
    Relation: MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
    Appears in Collections:[物理研究所] 期刊論文

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