Extended corona models of X-ray reverberation in the AGN 1H 0707−495 and IRAS 13224−3809

Abstract

ABSTRACTWe fit a new vertically extended corona model to previously measured reverberation time lags observed by XMM–Newton in two extremely variable narrow-line Seyfert 1 active galactic nuclei, 1H 0707−495 and IRAS 13224−3809, in a variety of similarly observed flux groups and explore the model in all observations over a 16 yr period. The model employs two X-ray sources located along the black hole rotational axis at height, h1 and h2, respectively. These sources have their associated photon indices Γ1 and Γ2 which respond to fluctuations in the disc with a maximum response duration of tmax and a propagation delay between the response of the two of tshift. We find that for 1H 0707−495, h2 is significantly correlated with Γ1 and anticorrelated with ionization ξ. Whilst the 1H 0707−495 corona extends upwards, the emission appears softer and the disc is less ionized. We find similarities in IRAS 13224−3809, but significant anticorrelation between Γ2 and both tmax and tshift. This suggests that when the IRAS 13224−3809 corona becomes softer while extending vertically upwards, the overall corona response occurs faster. This may also suggest that the inner disc also becomes more active. In addition, Γ1 and Γ2 are extreme, relatively less variable, but more separate in IRAS 13224−3809 than in 1H 0707−495. This suggests that the IRAS 13224−3809 corona may be more patchy in the sense that it has two more clear distinct spectral zones of Γ1 and Γ2 (possibly relating to two distinct zones of coronal temperature) when compared to 1H 0707−495.