Testing the Kerr nature of black hole candidates using iron line reverberation mapping in the Cardoso-Pani-Rico framework

Abstract

The iron Kα line commonly observed in the x-ray spectrum of black hole candidates is produced by x-ray fluorescence of the inner accretion disk. This line can potentially be quite a powerful tool to probe the spacetime geometry around these objects and test the Kerr black hole hypothesis. In a previous paper, we studied the ability to constrain possible deviations from the Kerr solution from the standard time-integrated iron line spectrum within the Cardoso-Pani-Rico framework. In the present work, we expand on that study and consider iron line reverberation mapping in the Cardoso-Pani-Rico framework. That is, we consider the time evolution of the iron line profile in response to fluctuations in the x-ray primary source. Our simulations clearly show that the time informatio n in reverberation mapping can better constrain the background metric than the time-integrated approach, and this is true, notably, for the deformation parameter ϵ[subscript 3][superscript r], which is only weakly informed by a time-integrated observation.