Constraining scalarization in scalar-Gauss-Bonnet gravity through binary pulsars

Abstract

In the present paper we derive strong constrains on scalarization in scalar-Gauss-Bonnet (SGB) gravity using observations of pulsars in close binary systems. Since scalarized neutron stars carry a nonzero scalar change, they emit scalar dipole radiation while inspiraling which speeds up the orbital decay. The observations support the conjecture that such radiation is either absent or very small for the observed binary pulsars. Using this, we determine the allowed range of parameters for SGB gravity. We also transfer the derived constraints to black holes in SGB gravity. It turns out that the maximum mass of a scalarized black hole cannot exceed roughly 10 to 20 solar masses, depending on the initial assumptions we make for the nuclear matter equations of state. The black hole scalar charge on the other hand can reach relatively large values that are potentially observable.