SimultaneousEUVE/ASCA/RXTEObservations of NGC 5548

J. Chiang, C. S. Reynolds, O. M. Blaes, M. A. Nowak, N. Murray, G. Madejski, H. L. Marshall, P. Magdziarz
2000 Astrophysical Journal  
We present simultaneous observations by EUVE, ASCA, and RXTE of the type 1 Seyfert galaxy NGC 5548. These data indicate that variations in the EUV emission (at ∼ 0.2 keV) appear to lead similar modulations in higher energy ( 1 keV) X-rays by ∼10--30 ks. This is contrary to popular models which attribute the correlated variability of the EUV, UV and optical emission in type 1 Seyferts to reprocessing of higher energy radiation. This behavior instead suggests that the variability of the optical
more » ... ty of the optical through EUV emission is an important driver for the variability of the harder X-rays which are likely produced by thermal Comptonization. We also investigate the spectral characteristics of the fluorescent iron Kα line and Compton reflection emission. In contrast to prior measurements of these spectral features, we find that the iron Kα line has a relatively small equivalent width (W_Kα∼ 100 eV) and that the reflection component is consistent with a covering factor which is significantly less than unity (Ω/2π∼ 0.4--0.5). Notably, although the 2--10 keV X-ray flux varies by ∼± 25 observations, the flux in the Fe Kα line is also constant. This behavior is difficult to reconcile in the context of standard Compton reflection models.
doi:10.1086/308178 fatcat:kvvl4542c5fa7byhhut732ibam