Tight constraints on Einstein-dilation-Gauss-Bonnet model with the GWTC-2 events.

Gravitational-wave data can be used to test general relativity in the extreme, highly nonlinear, and strong-field regime. Modified gravity theories such as Einstein-dilation-Gauss-Bonnet and dynamical Chern-Simons gravity are supposed to be well checked with some specific signals. We analyze gravitational-wave data from the first half of the third observing run of Advanced LIGO/Virgo to place constraints on the parameters of these two theories. The dynamical Chern-Simons gravity remains unconstrained. While for the Einstein-dilation-Gauss-Bonnet gravity, we have $\sqrt{\alpha_{\rm EdGB}}\lesssim 0.40\,\rm km$ with the data of GW190814 and $\sqrt{\alpha_{\rm EdGB}}\lesssim 0.24\,\rm km$ if GW190425 is a neutron star$-$black hole merger event, as allowed by the current observations. Such constraints are improved by a factor of $\sim 10-20$ in comparison to that set by the GWTC-1 events. We also demonstrate that the Bayes approach is more effective than the reweight method to constrain the Einstein-dilation-Gauss-Bonnet model.