From 3D hydrodynamic simulations of common-envelope interaction to gravitational-wave mergers

Abstract

Modelling the evolution of progenitors of gravitational-wave merger events in binary stars faces two major uncertainties: the commonenvelope phase and supernova kicks. These two processes are critical for the final orbital configuration of double compact-object systems with neutron stars and black holes. Predictive one-dimensional models of common-envelope interaction are lacking and multidimensional simulations are challenged by the vast range of relevant spatial and temporal scales. Here, we present three-dimensional, magnetohydrodynamic simulations of the common-envelope interaction of an initially 10 M red supergiant primary star with a blackhole and a neutron-star companion. Employing the moving-mesh code arepo and replacing the core of the primary star and the companion with point masses, we show that the high-mass regime is accessible to full ab initio simulations. About half of the common envelope is dynamically ejected at the end of our simulations and the ejecta mass fraction keeps growing. Almost complete envelope ejection seems possible if all ionised gas left over at the end of our simulation eventually recombines and the released energy continues to help unbind the envelope. We find that the dynamical plunge-in of both companions terminates at orbital separations that are too wide for gravitational waves to merge the systems in a Hubble time. However, the orbital separations at the end of our simulations are still decreasing such that the true final value at the end of the common-envelope phase remains uncertain. We discuss the further evolution of the system based on analytical estimates. A subsequent mass-transfer episode from the remaining 3 M core of the supergiant to the compact companion does not shrink the orbit sufficiently either. A neutron-star-neutron-star and neutronstar-black-hole merger is still expected for a fraction of the systems if the supernova kick aligns favourably with the orbital motion. For double neutron star (neutron-star-black-hole) systems we estimate mergers in about 9% (1%) of cases while about 77% (94%) of binaries are disrupted; that is, supernova kicks actually enable gravitational-wave mergers in the binary systems studied here. Assuming orbits smaller by one-third after the common-envelope phase enhances the merger rates by about a factor of two. However, the large post-common-envelope orbital separations found in our simulations mean that a reduction in predicted gravitational-wave merger events appears possible.

Three-dimensional simulations of the jet feedback mechanism in common envelope jets supernovae

“…The limited number of 3D hydrodynamical simulations of the CEE (and the grazing envelope evolution) that do include jets launched by the companion (e.g., Moreno Méndez et al 2017;Shiber & Soker 2018;López-Cámara et al 2019;Schreier et al 2019;Shiber et al 2019;López-Cámara et al 2020;Lopez-Camara et al 2022;Zou et al 2022;Schreier, Hillel, & Soker 2023) are far from revealing all aspects of jet-powered CEE (see for a review of processes due to jets that NS/BH launch in CEE and possible outcomes). A different class of simulations (e.g., Zou et al (2020); Moreno et al (2022)) study collimated outflow from the distorted envelope at the final phases of the CEE (similar to the suggestion by Soker 1992), but this setting is not related to the present study.…”

Gravitational wave emission from dynamical stellar interactions

“…As indicated by Renzo et al (2021), the final orbit resulting from a CE ejection has to shrink below one solar radius to be in a frequency range where LISA has a chance to detect them. Unfortunately, we do not observe a sufficient orbital shrinkage in this simulation or in any of the other simulations resulting in successful CE ejection that we analyzed (Sand et al 2020;Ondratschek et al 2022;Moreno et al 2022). Therefore, we do not obtain any detectable GW signal from the dynamical phase of successful CE ejections for the LISA mission.…”

“…dominant, GWs provide an interesting opportunity for observing such short-lived and elusive events. Three-dimensional hydrodynamic (3D HD) or magnetohydrodynamic (3D MHD) simulations are one of the most reliable (albeit expensive) ways of modeling CE events (see Ricker & Taam 2012;Ohlmann et al 2016;Staff et al 2016;Prust & Chang 2019;Reichardt et al 2019;Sand et al 2020;Chamandy et al 2020;Reichardt et al 2020;Moreno et al 2022;Glanz & Perets 2021;Lau et al 2022a,b;Zou et al 2022;Ondratschek et al 2022, for some recent examples) and mergers between different types of stars, such as main-sequence (MS) stars (Schneider et al 2019) and white dwarfs (Munson et al 2021;Dan et al 2012;Zhu et al 2015). In setups in which general relativity (GR) is dynamically not relevant, these methods provide the most consistent predictions of the merger process, and GWs can be derived from these simulations, but this has rarely been done.…”

Jet-powered Turbulence in Common Envelope Evolution

“…The limited number of 3D hydrodynamical simulations of CEE (and grazing envelope evolution, GEE) that do include jets launched by the companion (e.g., Moreno Méndez et al 2017;Shiber & Soker 2018;López-Cámara et al 2019, 2022Schreier et al 2019;Shiber et al 2019;Zou et al 2022;Schreier et al 2023) are far from revealing all aspects of jet-powered CEE (see Soker 2022 for a review of the processes due to jets that NS/ BH launch in CEE and the possible outcomes). A different class of simulations (e.g., Zou et al 2020;Moreno et al 2022;Ondratschek et al 2022) study collimated outflows from the distorted envelope at the final phases of CEE (similar to the suggestion by Soker 1992), but this setting is not related to the present study.…”