Title: An X-Ray Spectral and Temporal Model for Clumpy Tori in Active Galactic Nuclei

Speaker: 刘元 副研究员
Institute: 中国科学院高能物理研究所(IHEP)
Time: 2017.11.17(Friday) 14:30
Place: Physics Building 573, Haiyun Campus, Xiamen University

Abstract: We recently construct an X-ray spectral model for the clumpy torus in an active galactic nucleus (AGN) using Geant4 (Liu, Y., & Li, X. 2014, ApJ, 787, 52; Liu, Y., & Li, X. 2015, MNRAS, 448, L53; Liu, Y., & Li, X. 2016, ApJ, 828, 114) and investigate the effect of the clumpiness parameters on the reflection spectra and the strength of the fluorescent line Fe Kα. The volume filling factor of the clouds in the clumpy torus only slightly influences the reflection spectra, however, the total column density and the number of clouds along the line of sight significantly change the shapes and amplitudes of the reflection spectra. The effect of column density is similar to the case of a smooth torus, while a small number of clouds along the line of sight will smooth out the anisotropy of the reflection spectra and the fluorescent line Fe Kα. The smoothing effect is mild in the low column density case (NH=10^23 cm^-2), whereas it is much more evident in the high column density case (NH=10^25 cm^-2). Our model provides a quantitative tool for the spectral analysis of the clumpy torus. We have applied it to the NuSTAR spectra of NGC 1068 and found a small number of clouds along the line of sight is preferred. We will also discuss the temporal model for clumpy tori and its application in the reverberation of narrow Fe Kα line (Liu, Y., & Li, X. 2017, ApJ, 844, 8).

(The speaker will also introduce some preliminary results of Insight-HXMT)