Mullard Space Science Laboratory

E. M. Puchnarewicz
Multiwavelength studies of ultra-soft X-ray AGN

1992 (supervisor: K. O. Mason)

I investigate the X-ray, optical and infra-red properties of the 53 AGN identified as part of the Einstein Ultra-Soft Survey (USS). Of all sources in the IPC database, these have the strongest, distinct soft X-ray excesses at 0.25 keV.

The IPC data are modelled using two separate components, the `soft' and `hard' X-ray components. Continuum and line parameters are measured from optical spectra while CCD images provide accurate magnitudes and information on the AGN morphology and environment. Infra-red fluxes of the nucleus and the underlying galaxy are measured from UKIRT images. Multiwavelength spectra, combining IR, optical, UV and X-ray data, are presented for thirteen AGN.

I find that approximately one third of USS AGN are hard X-ray quiet; the remaining hard X-ray fluxes are typical of other X-ray selected AGN. All optical and IR continuum luminosities are `normal'. A striking characteristic of the sample is the high proportion of narrow-line objects it contains; I also find that the permitted lines are weak. Optical FeII emission is strong where hard X-rays are weak, contradicting hard X-ray dependent models for their production.

All results are considered in the context of two models for the production of a strong soft X-ray flux, accretion disks and the cool clouds model of Guilbert and Rees. The narrow lines suggest that we may be seeing a flattened BLR face-on - alternatively, the BLR may lie further from the black hole than for other AGN. An association of a face-on BLR with an accretion disk would strongly favour geometrically thick disks over thin. The overall spectral distribution can also be well reproduced by the cool clouds model.


Mullard Space Science Laboratory - Holmbury St Mary - Dorking - Surrey - RH5 6NTTelephone: +44 (0) 1483 204100 - Copyright © 1999-2005 UCL

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