Gravitational waves from eccentric binary neutron star mergers: Systematic biases and inadequacy of quasicircular templates

The use of quasicircular waveforms in matched-filter analyses of signals from eccentric binary neutron star (BNS) mergers can lead to biases in the source’s parameter estimation. We demonstrate that significant biases can be present already for moderate eccentricities <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"> <a:msub> <a:mi>e</a:mi> <a:mn>0</a:mn> </a:msub> <a:mo>≳</a:mo> <a:mn>0.05</a:mn> </a:math> and signals detected by LIGO-Virgo-KAGRA with signal-to-noise ratio (SNR) <c:math xmlns:c="http://www.w3.org/1998/Math/MathML" display="inline"> <c:mo>≳</c:mo> <c:mn>12</c:mn> </c:math> . We perform systematic Bayesian mock analyses of unequal-mass nonspinning BNS signals up to eccentricities <e:math xmlns:e="http://www.w3.org/1998/Math/MathML" display="inline"> <e:msub> <e:mi>e</e:mi> <e:mn>0</e:mn> </e:msub> <e:mo>∼</e:mo> <e:mn>0.1</e:mn> </e:math> using quasicircular effective-one-body (EOB) waveforms with spins. We find fractional SNR losses up to tens of percent and up to <g:math xmlns:g="http://www.w3.org/1998/Math/MathML" display="inline"> <g:mrow> <g:mn>16</g:mn> <g:mi>σ</g:mi> </g:mrow> </g:math> deviations in the inference of the chirp mass. The latter effect is sufficiently large to lead to an incorrect (and ambiguous) source identification. The inclusion of spin precession in the quasicircular waveform does not capture eccentricity effects. We conclude that high-precision observations with advanced (and next generation) detectors are likely to require standardized, accurate, and fast eccentric waveforms.