Two-body problem in curved spacetime: exploring gravitational wave transient cases

We compare two versions of the GW150914 gravitational wave signal analysis by the LIGO/Virgo collaboration. The first version was published in 2016 by this collaboration along with their announcement of the first experimental detection of gravitational waves. It was based on the gravitational wave waveforms with the fully non-linear general-relativistic treatment of the coalescing two-body problem. The second analysis of this signal by the same authors, published in 2017, was based on the quadrupole post-Newtonian (PN) flat spacetime approximation of General Relativity. The authors had shown that the PN-based mass estimation of the system coincide with that obtained by using rigorous relativistic treatment in their first publication. In our view, this coincidence implies that the rigorous non-linear theory for gravitational waveforms of coalescing blackhole binaries does not fully account for the difference between the source and detector reference frames - because the PN-approximation, which is used for the comparison, does not make any distinction between these two reference frames: by design and by the principles and conditions for building the PN-approximation. We discuss possible implications of this conflict and find that the accuracy of most of the previously estimated characteristic (chirp) masses of coalescing binary blackhole systems is likely to be affected by a substantial systematic error. The corresponding luminosity distances of these sources also turn out to be overestimated.