Projecting the likely importance of weak-interaction-driven bulk viscosity in neutron star mergers

Elias R. Most, Steven P. Harris, Christopher Plumberg, Mark G. Alford, Jorge Noronha, Jacquelyn Noronha-Hostler, Frans Pretorius, Helvi Witek, Nicolás Yunes

Research output: Contribution to journalArticlepeer-review

41 Scopus citations


In this work, we estimate how ch bulk viscosity driven by Urca processes is likely to affect the gravitational wave signal of a neutron star coalescence. In the late inspiral, we show that bulk viscosity affects the binding energy at fourth post-Newtonian order. Even though this effect is enhanced by the square of the gravitational compactness, the coefficient of bulk viscosity is likely too small to lead to observable effects in the wavefo during the late inspiral, when only considering the orbital motion itself. In the post-merger, however, the characteristic time-scales and spatial scales are different, potentially leading to the opposite conclusion. We post-process data from a state-of-the-art equal-mass binary neutron star merger silation to estimate the effects of bulk viscosity (which was not included in the silation itself). In that scenario, we find that bulk viscosity can reach high values in regions of the merger. We compute several estimates of how ch it might directly affect the global dynamics of the considered merger scenario, and find that it could become significant. Even larger effects could arise in different merger scenarios or in silations that include non-linear effects. This assessment is reinforced by a quantitative comparison with relativistic heavy-ion collisions where such effects have been explored extensively.

Original languageEnglish (US)
Pages (from-to)1096-1108
Number of pages13
JournalMonthly Notices of the Royal Astronomical Society
Issue number1
StatePublished - Jan 1 2022

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science


  • gravitational waves
  • hydrodynamics
  • methods
  • neutrinos
  • neutron star mergers
  • numerical
  • relativistic processes


Dive into the research topics of 'Projecting the likely importance of weak-interaction-driven bulk viscosity in neutron star mergers'. Together they form a unique fingerprint.

Cite this