Singularity-free black holes in conformal gravity: New observational constraints

We consider the family of singularity-free rotating black hole solutions in Einstein's conformal gravity found in BAMBI C. et al., JCAP, 05 (2017) 003 and we constrain the value of the conformal parameter L from the analysis of a 30 \text{ks} NuSTAR observation of the stellar-mass black hole in GS 1354-645 during its outburst in 2015. Our new constraint is much stronger than that found in previous work. Here we obtain L/M < 0.12 (99% confidence level, statistical uncertainty only).