Robust and improved constraints on higher-curvature gravitational effective-field-theory with the GW170608 event

Effective field theory methods allow us to modify general relativity through higher-curvature corrections to the Einstein-Hilbert action, while preserving Lorentz invariance and the number of gravitational degrees of freedom. We here construct an approximate inspiral-merger-ringdown waveform model within the cubic, parity-preserving class of effective-field-theory extensions to Einstein's theory for the gravitational waves emitted by quasicircular binary black holes with aligned/antialigned spins. Using this waveform model, we first explore the detectability of non-Einsteinian effective-field-theory effects through an extended version of effective cycles to illustrate the need to include non-Einsteinian amplitude corrections. We then use this model to analyze the GW170608 event in a full Bayesian framework, and we place new improved and more robust constraints on the coupling constants of the effective field theory. Our Bayesian model selection study disfavors the non-Einsteinian theory with a (log) Bayes factor of $\mathrm{log}{\mathcal{B}}_{\mathrm{GR}}^{\mathrm{EFT}}=\ensuremath{-}2.81$. Our Bayesian parameter estimation study places the constraints ${\overline{\ensuremath{\alpha}}}_{1}=0.8{7}_{\ensuremath{-}1.03}^{+1.95}$ and ${\overline{\ensuremath{\alpha}}}_{2}=\ensuremath{-}0.3{5}_{\ensuremath{-}2.92}^{+4.12}$ at 90% confidence on the coupling parameters of the effective-field theory. These constraints are 3.5 stronger than previous constraints, informative relative to the prior, and independent of the choice of prior on the coupling parameters of the modified theory.