Quasar continuum spectrum disfavors black holes with a magnetic monopole charge

TL;DR

This study compares theoretical spectra of Bardeen black holes with magnetic monopole charge to optical quasar data, finding that standard Kerr black holes are more consistent with observations than monopole-charged black holes.

Contribution

The paper derives the accretion disk spectrum for Bardeen black holes and uses observational data to constrain the monopole charge, providing the first observational limits on such charges.

Findings

Kerr black holes are more favored than monopole-charged black holes.

Black holes with monopole charge g ≥ 0.03 are outside 99% confidence interval.

Observational data disfavors black holes with significant magnetic monopole charge.

Abstract

Black holes carrying a magnetic monopole charge are a subject of interest for a long time. In this work we explore the possibility of an observational evidence of such black holes carrying a magnetic monopole, namely the Bardeen rotating black holes. We derive the theoretical spectrum from the accretion disk surrounding a Bardeen black hole using the thin-disk approximation. We compare the theoretically derived spectrum in comparison to the optical data of eighty Palomar Green quasars to constrain the monopole charge parameter $g$ and the spin parameter $a$ of the quasars. From our analysis we note that the Kerr-scenario in \gr\ is observationally more favored than black holes with a monopole charge. We arrive at such a conclusion using error estimators like $\chi^2$, the Nash-Sutcliffe efficiency, the index of agreement and their modified forms. In particular, black holes with $g \geq 0.03$ are outside $99\%$ confidence interval. The implications are discussed.