Ultrasoft X-ray components in the high-temperature extreme

被引:2
作者
Puchnarewicz, EM [1 ]
机构
[1] UCL, Mullard Space Sci Lab, Dorking RH5 6NT, Surrey, England
关键词
accretion; accretion discs; galaxies : active; galaxies : Seyfert; X-rays : galaxies;
D O I
10.1046/j.1365-8711.1998.01827.x
中图分类号
P1 [天文学];
学科分类号
0704 ;
摘要
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(0.1-2keV)similar to 2 x 10(45) 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.
引用
收藏
页码:299 / 304
页数:6
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