Bounding the boundless: constraining topological Gauss-Bonnet coupling from GW150914

Recent gravitational wave observation based on the data from GW150914 has firmly confirmed Hawking's area theorem and estimated the increase in total horizon area during a merger process of two Kerr black holes. We use this result to obtain the first observational bound on the 4D topological Gauss-Bonnet coupling as γ≲γmax≈2.804+3.739−2.804×109m2 at 90% credibility.