Fermion-axion stars: Static solutions and dynamical stability

We construct spherically symmetric static solutions of the Einstein-Klein-Gordon-Euler system involving a complex scalar field governed by periodic potential that emerges in models axionlike particles and fermionic matter modeled perfect fluid with polytropic equation state. Such describe gravitationally bound composites fermions axions, which we dub fermion-axion stars. Sequences pure axion stars existence domain may show presence multiple stable branches depending on value decay constant parameter potential; this reflects appearance islands stability two-dimensional space configurations. investigate for three different values constant, identifying one or more regions linear stability, making use method already employed previous works. confirm results from analysis performing fully nonlinear numerical relativity evolutions. In context, perform several simulations to identify where unstable face fates: collapse Schwarzschild black hole, migration model, finally dispersion together dilution matter, approaches fermion star model very low mass. This latter scenario was never observed without potential.