Tidal Deformabilities of Neutron Stars in scalar-Gauss-Bonnet Gravity and Their Applications to Multimessenger Tests of Gravity

The spacetime surrounding compact objects such as neutron stars and black holes provides an excellent place to study gravity in the strong, non-linear, dynamical regime.  Here, the effects of strong curvature can leave their imprint on observables which we may use to study gravity. Recently, NICER provided a mass and radius measurement of an isolated neutron star, while LIGO/Virgo measured the tidal deformability of neutron stars. These measurements can be used to test the relation between the tidal deformability and compactness of neutron stars that are known to be universal in general relativity. In this talk, I will discuss how we constructed tidally-deformed neutron star solutions and expanded upon the observations of NICER and LIGO/Virgo to investigate universal relations in scalar-Gauss Bonnet gravity.  We find that the relation between the tidal deformability and compactness remains to be mostly universal for a fixed dimensionless coupling constant.  For the equations of state considered, it remains inconclusive whether one can place a meaningful bounds on scalar Gauss-Bonnet gravity with the new universal relations. However, we found a new bound from the mass measurement of the pulsar J0740+6620 that is comparable to other existing bounds from black hole observations.