Ultrasoft X-ray components in the high-temperature extreme
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(0.1-2keV)~2x10^45ergs^-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.
- Publication:
-
Monthly Notices of the Royal Astronomical Society
- Pub Date:
- August 1998
- DOI:
- 10.1046/j.1365-8711.1998.01827.x
- Bibcode:
- 1998MNRAS.299..299P
- Keywords:
-
- ACCRETION;
- ACCRETION DISCS;
- GALAXIES: ACTIVE;
- GALAXIES: SEYFERT;
- X-RAYS: GALAXIES