Testing conformal gravity with the supermassive black hole in 1H0707-495

Abstract

Recently, two of us have found a family of singularity-free rotating black hole solutions in Einstein's conformal gravity. These spacetimes are characterized by three parameters: the black hole mass $M$, the black hole spin angular momentum $J$, and a parameter $L$ that is not specified by the theory but can be expected to be proportional to the black hole mass $M$. The Kerr black hole solution of Einstein's gravity is recovered for $L=0$. In a previous paper, we showed that X-ray data of astrophysical black holes require $L/M<1.2$. In the present paper, we report the results of a more sophisticated analysis. We apply the X-ray reflection model relxill_nk to NuSTAR and Swift data of the supermassive black hole in 1H0707--495. We find the constraint $L/M<0.45$ (90% confidence level).