Abstract
RE J2248-511 is one of only 14 non-blazar AGN detected in the far ultraviolet by the ROSAT Wide Field Camera implying a large ultrasoft X-ray flux. This soft X-ray excess is strongly variable on year timescales, a common property of Narrow Line Seyfert 1s, yet its optical linewidths classify this source as a broad-lined Seyfert 1. We use four nearly simultaneous optical--X-ray SEDs spanning 7 years to study the spectral shape and long term variability of RE J2248-511. Here we show that the continuum SED for the brightest epoch dataset is consistent with the mean SED of a standard quasar, and matches well to that from an XMM-SDSS sample of AGN with <M/M_Sun> ~ 10^8 and <L/L_Edd> ~ 0.2. All the correlated optical and soft X-ray variability can be due entirely to a major absorption event. The only remarkable aspect of this AGN is that there is no measurable intrinsic X-ray absorption column in the brightest epoch dataset. The observed FUV flux is determined by the combination of this and the fact that the source lies within a local absorption `hole'. RE J2248-511, whose variable, ultrasoft X-ray flux once challenged its BLS1 classification, demonstrates that characterisation of such objects requires multi-epoch, multi-wavelength campaigns.
Highlights
The ultraviolet (UV) to X-ray spectral shapes seen in active galactic nuclei (AGN) clearly comprise multiple components and have been the subject of decades of study
We note that Puchnarewicz et al (1995) performed spectral energy distributions (SEDs) fitting of the 1993 Position Sensitive Proportional Counters (PSPC) spectrum with the ROSAT Wide Field Camera (WFC) point and an optical spectrum taken 2 yr previously with the South African Astronomical Observatory (SAAO) 1.9-m Radcliffe telescope, and found an optical continuum rising to the blue and forming a big blue bump with the soft X-ray data
The optical to X-ray SED of RE J2248−511 can be well represented by a colour–temperature corrected accretion disc spectrum with Comptonization of both low temperature optically thick disc material and high temperature optically thin material in a corona, plus a reflection component which is evident above 5 keV
Summary
The ultraviolet (UV) to X-ray spectral shapes seen in active galactic nuclei (AGN) clearly comprise multiple components and have been the subject of decades of study. The narrow-line Seyfert 1 (NLS1) subclass, objects where the full width at half-maximum (FWHM) of the broad component of the Hβ line is ≤2000 km s−1 (Osterbrock & Pogge 1985), shows nearly ubiquitous strong, steep soft X-ray emission (Boller, Brandt & Fink 1996; Grupe et al 1999). These are most probably lowmass black holes accreting at high mass accretion rates with respect to Eddington (L/LEdd ∼ 1; Boroson 2002), so much of the soft.
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