Slowly rotating black holes in the novel Einstein–Maxwell-scalar theory

We investigate a slowly rotating black hole solution in novel Einstein-Maxwell-scalar theory, which is prompted by the classification of general theories. The gyromagnetic ratio this calculated, and it increases as second free parameter $\beta$ increases, but decreases with increasing $\gamma\equiv \frac{2 \alpha^{2}}{1+\alpha^2}$. In Einstein-Maxwell-dilaton (EMD) vanishes, $\alpha$ governing strength coupling between dilaton Maxwell field remains. always less than $2$, well-known value for Kerr-Newman (KN) well Dirac electron. Scalar hairs reduce magnetic dipole moment resulting drop ratio. However, we find that two can be realized theory charge-to-mass $Q/M$ simultaneously (recall KN holes independent $Q/M$). same situation also applies to angular velocity locally non-rotating observer. Moreover, analyze period correction circular orbits terms ratio, radius innermost stable orbits. It found $Q/M$. Finally, total radiative efficiency investigated, vanish once effect rotation considered.