2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/95273The effect of a soft phase core appearance in the center of polytropic star is analyzed by means of linear response theory. Approximate formulae for the changes of radius, moment of inertia and mass-energy of non-rotating configuration with arbitrary adiabatic indices are presented, followed by an example evaluation of astrophysical observables.9 pages, 2 figures, submitted to APP BAstrophysicstext