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Paper   IPM / Astronomy / 16126
School of Astronomy
  Title:   Testing Ghasemi-Nodehi-Bambi spacetime with continuum-fitting method
  Author(s):  M. Ghasemi-Nodehi
  Status:   Published
  Journal: Eur. Phys. J. C
  Year:  2020
  Supported by:            ipm IPM
The continuum-fitting method is the analysis of the thermal spectrum of the geometrically thin and optically thick accretion disk around stellar-mass black holes. A parametrization aiming to test the Kerr nature of astrophysical black holes was proposed in Ghasemi-Nodehi and Bambi in EPJC 76:290, 2016. The metric contains 11 parameters in addition to the mass and spin parameters. One can recover the Kerr case by setting all parameters to one. In this paper, I study the continuum-fitting method in a Ghasemi-Nodehi�??Bambi background. I show the impact of each of the parameters on the spectra. I then employ �?2 studies and show that using the continuum-fitting method all parameters of Ghasemi-Nodehi�??Bambi spacetime are degenerate. However, the parameter b9 can be constrained in the case of a high spin value and the Ghasemi-Nodehi�??Bambi black hole as reference. This degeneracy means that the spectra of the Kerr case cannot be distinguished from spectra produced in Ghasemi-Nodehi�??Bambi spacetime. This is a problem as regards measuring the spin of astrophysical black holes and constrain possible deviations from the Kerr case of General Relativity

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