Discrepancy in tidal deformability of GW170817 between the Advanced LIGO twins

Tatsuya Narikawa, Nami Uchikata, Kyohei Kawaguchi, Kenta Kiuchi, Koutarou Kyutoku, Masaru Shibata, Hideyuki Tagoshi

Published 2018-12-14Version 1

We find that the Hanford and Livingston detectors of Advanced LIGO derive distinct posterior probability distribution of binary tidal deformability tilde{Lambda} of the first binary-neutron-star merger GW170817. Analyzing public data of GW170817 with a nested-sampling engine and the default TaylorF2 waveform provided by the LALInference package, we obtain significantly multimodal distribution characterized by a disconnected highest-posterior-density 90% credible interval from the Livingston detector. Furthermore, the distribution derived by the Livingston detector changes irregularly when we vary the maximum frequency of the data used in the analysis. These features are not observed for the Hanford detector. By imposing the flat prior on tidal deformability of individual stars, symmetric 90% credible intervals of tilde{Lambda} are estimated to be 234^{+960}_{-172} with the Hanford detector, 1639^{+578}_{-1193} with the Livingston detector, and 183^{+993}_{-130} with the LIGO-Virgo detector network. While they are all consistent, the discrepancy and irregular behavior suggest that an in-depth study of noise properties might improve our understanding of GW170817 and future events.