Gravitational waves from the collapse and bounce of a stellar core in tensor-scalar gravity

Tensor-scalar theory of gravity allows the generation of gravitational wave s from astrophysical sources, like supernovae, even in the spherical case. That motivated us to study the collapse of a degenerate stellar core, withi n tensor-scalar gravity, leading to the formation of a neutron star through a bounce and the formation of a shock. This paper discusses the effects of the scalar field on the evolution of the system, as well as the appearance of strong nonperturbative effects of this scalar field (the so-called spon taneous scalarization). As a main result, we describe the resulting gravita tional monopolar radiation (form and amplitude) and discuss the possibility of its detection by the gravitational detectors currently under constructi on, taking into account the existing constraints on the scalar field. From the numerical point of view, it is worthy to point out that we have develop ed a combined code that uses pseudospectral methods for the evolution of th e scalar field and High-Resolution Shock-Capturing schemes, as well as for the evolution of the hydrodynamical system. Although this code has been use d to integrate the field equations of that theory of gravity, in the spheri cally symmetric case, a by-product of the present work is to gain experienc e for an ulterior extension to multidimensional problems in Numerical Relat ivity of such numerical strategy.