Scalar hairy black holes in Einstein-Maxwell-conformally coupled scalar theory

We obtain scalar hairy black holes from Einstein-Maxwell-conformally coupled scalar (EMCS) theory with the scalar coupling parameter alpha to the Maxwell term. In case of alpha = 0, the alpha = 0 EMCS theory provides constant (charged) scalar hairy black hole and charged BBMB (Bocharova-Bronnikov-Melnikov-Bekenstein) black hole where the former is stable against full perturbations, while the latter remains unstable because it belongs to an extremal black hole. It is noted that for alpha not equal 0, the unstable Reissner-Nordstrom black holes without scalar hair imply infinite branches of n = 0(alpha >= 8.019), 1(alpha >= 40.84), 2(alpha >= 99.89), ... scalarized charged black holes. In addition, for alpha > 0, we develop a single branch of scalarized charged black hole solutions inspired by the constant scalar hairy black hole. Finally, we obtain the numerical charged BBMB black hole solution from the alpha = 0 EMCS theory. (C) 2020 The Authors. Published by Elsevier B.V.