Dr. Subhankar Patra

Non-Kerr black holes in alternative gravity theory include parametric deviations to the usual Kerr spacetime. Moreover, these objects are consistent with the modern-day observations of black holes both in electromagnetic and gravitational-wave signals. Therefore, we cannot rule out the possibility of alternative gravity theory compared to the well-known Einstein's gravity theory unless we have precise observational data. In the literature, many theoretical predictions of various astrophysical phenomena exist for the non-Kerr spacetime. However, the hydrodynamic aspects of transonic accretion flow around these black holes have not yet been addressed. In my talk, I will discuss the properties of accretion solutions around two renowned non-Kerr black holes: the Johannsen-Psaltis (JP) black holes and the Konoplya-Rezzolla-Zhidenko (KRZ) black holes, using the framework of general relativistic hydrodynamics. From this analysis, I will aim to isolate the type of parametric deviations from the Kerr metric. I will conclude my talk by phenomenologically showing that the non-Kerr black holes are consistent with the observed high-frequency QPOs commonly detected in AGN and black hole X-ray binaries.