XSPEC model for testing the Kerr black hole hypothesis using the continuum-fitting method

Understand

We present NKBB, an XSPEC model for the thermal spectrum of thin accretion disks in parametric black hole spacetimes.

• We employ the Novikov-Thorne model for the description of the accretion disk and the formalism of the transfer function proposed by Cunningham for storing all the relativistic effects of the spacetime metric.
• The current version of the model assumes the Johannsen metric, but it can be easily extended to any stationary, axisymmetric, and asymptotically-flat spacetime without pathological properties.
• The model can be used within the XSPEC package to test the Kerr nature of astrophysical black holes with the continuum-fitting method.