GW170817 and GW190814: Tension on the Maximum Mass

The detection of the binary events GW170817 and GW190814 has provided invaluable constraints on the maximum mass of nonrotating configurations of neutron stars, M-TOV. However, the large differences in the neutron-star masses measured in GW170817 and GW190814 has also lead to significant tension between the predictions for such maximum masses, with GW170817 suggesting that M-TOV less than or similar to 2.3 M-circle dot, and GW190814 requiring M-TOV greater than or similar to 2.5 M-circle dot if the secondary was a (non- or slowly rotating) neutron star at merger. Using a genetic algorithm, we sample the multidimensional space of parameters spanned by gravitational-wave and astronomical observations associated with GW170817. Consistent with previous estimates, we find that all of the physical quantities are in agreement with the observations if the maximum mass is in the range of M-TOV = 2.210(-0.123)(+0.116) M-circle dot within a 2 sigma confidence level. By contrast, maximum masses with M-TOV greater than or similar to 2.5 M-circle dot, not only require efficiencies in the gravitational-wave emission that are well above the numerical-relativity estimates, but they also lead to a significant underproduction of the ejected mass. Hence, the tension can be released by assuming that the secondary in GW190814 was a black hole at merger, although it could have been a rotating neutron star before.

Automated summary

The detection of the binary events GW170817 and GW190814 has provided important constraints on the maximum mass of nonrotating configurations of neutron stars, but the significant tension between the predictions due to large differences in measured neutron-star masses requires further research for resolution.