Measuring eccentricity of binary black holes in GWTC-1 by using inspiral-only waveform

Abstract

In this paper, we estimate the eccentricity of the 10 BBHs in GWTC-1 by using the inspiral-only BBH waveform template EccentricFD. Firstly, we test our method with simulated eccentric BBHs. Afterwards we apply the method to the real BBH gravitational wave data. We find that the BBHs in GWTC-1 except GW151226, GW170608 and GW170729 admit almost zero eccentricity. Their upper limits on eccentricity rang from 0.033 to 0.084 with 90% credible interval at the reference frequency 10Hz. And their median eccentricities are 0.000. For GW151226, GW170608 and GW170729, the upper limits are higher than 0.1. But the median eccentricities are respectively 0.000, 0.064 and 0.000. We also point out the limitations of the inspiral-only waveform template in eccentricity measurement. The current eccentricity measurement results of GWTC-1 is not enough to constrain the formation mechanisms of BBHs, and more observational data are needed in the future.