The merger between a neutron star and a black hole within a dense stellar environment might not emit the electromagnetic radiation seen when the same process occurs in an isolated environment, according to a modelling paper published in Communications Physics. A merger within a dense environment might also exhibit two additional distinct signatures compared to an isolated merger. These findings may provide useful insights into interpreting future observations of gravitational waves.
The detection of gravitational waves emitted during a neutron star - black hole merger can provide a wealth of information about stellar evolution, nuclear matter, and General Relativity. Although the theoretical framework about neutron star - black hole mergers has been established, how these two bodies interact within a dense stellar environment during this process is unclear.
Manuel Arca Sedda used detailed simulations to model the formation of a neutron star - black hole merger. He then combined the simulations with observations of star clusters in the Milky Way and in the local Universe. Arca Sedda found that the system resulting from the merger of the two massive bodies within a dense environment may be different from a similar system formed in an isolated environment. He found that mergers occurring in dense environments have larger total mass and heavier black holes, possibly not emitting radiation - or light - during or promptly after the merger. The findings suggest that if a merger were to occur within a dense stellar environment, it might only be detectable by telescopes searching for gravitational waves.
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