Testing the Kerr black hole hypothesis with the continuum-fitting and the iron line methods: the case of GRS 1915+105

Understand

The continuum-fitting and the iron line methods are currently the two leading techniques for probing the strong gravity region around accreting black holes.

• In the present work, we test the Kerr black hole hypothesis with the stellar-mass black hole in GRS 1915+105 by analyzing five disk-dominated RXTE spectra and one reflection-dominated Suzaku spectrum.
• The combination of the constraints from the continuum-fitting and the iron line methods has the potential to provide more stringent tests of the Kerr metric.
• Our constraint on the Johannsen deformation parameter $\alpha_{13}$ is $-0.15 < \alpha_{13} < 0.14$ at 3$\sigma$, where the Kerr metric is recovered when $\alpha_{13} = 0$.