Ultrasoft X-ray components in the high-temperature extreme |
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| Authors: | E M Puchnarewicz |
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| Institution: | Mullard Space Science Laboratory, University College London, Holmbury St. Mary, Dorking, Surrey RH5 6NT |
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| Abstract: | A search for high-redshift ( z > 0.5) ultrasoft X-ray AGN in pointed ROSAT PSPC observations is made, using the wgacat catalogue. Evidence for a further three such objects is found, adding to three identified previously (E1346+266, EXO 1346.4+2637 and RX J0947.0+4721). The flux of one new object 1WGA J1342.4+2720; L (0.1–2 keV)∼ 2 × 1045 erg s−1)] was found to be variable (a factor of 1.7 over 2 d), and this object has relatively narrow permitted line emission. These properties, also seen in E1346+266 and EXO 1346.4+2637, are typical of ultrasoft AGN at all redshifts, in particular the narrow-line Seyfert 1s (NLS1s). The rarity of high- z ultrasoft AGN places limits on the 'temperature' of the soft X-ray component in the rest frame of AGN in general. It also provides an opportunity to investigate models for the soft component in the high-temperature extreme, e.g., for accretion disc models, testing the physics at the inner edge of the disc, and the effects of Comptonization in a hot, optically thin corona. |
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| Keywords: | Accretion Accretion discs Galaxies: Active Galaxies: Seyfert X-rays: galaxies |
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