2023MNRAS.520..180H

We 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 t_max and a propagation delay between the response of the two of t_shift. 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 t_max and t_shift. 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.