We present simple XSPEC models for fitting excess variance spectra of AGN. Using a simple Monte-Carlo approach, we simulate a range of spectra corresponding to physical parameters varying, then calculate the resulting variance spectra. Starting from a variable power-law, we build up a set of models corresponding to the different physical processes that can affect the final excess variance spectrum. We show that the complex excess variance spectrum of IRAS 13224-3809 can be well described by such an intrinsic variability model, where the power-law variability is damped by relativistic reflection and enhanced by an ultra fast outflow. The reflection flux is correlated with that of the power-law, but not perfectly. We argue that this correlation is stronger at high frequencies, where reverberation lags are detected, while excess variance spectra are typically dominated by low frequency variability.
@article{arxiv.1910.12808,
title = {Modelling X-ray RMS spectra I: intrinsically variable AGN},
author = {M. L. Parker and W. N. Alston and Z. Igo and A. C. Fabian},
journal= {arXiv preprint arXiv:1910.12808},
year = {2020}
}
Comments
8 pages, 4 figures, accepted for publication in MNRAS. Updated to accepted version