The fate of a residue is dictated by the mass of the two merging neutron stars and the maximum mass a neutron star can support before it collapses to form a black hole. If the residue is more massive than the maximum mass threshold, there are 2 possibilities: if the residue mass is up to 20% more than the optimum mass limit, it makes it through as a neutron star for hundreds to thousands of seconds prior to collapsing into a black hole.
Observations of other neutron stars in our Galaxy and a number of constraints on the behavior of nuclear matter suggest that the maximum mass limit for a neutron star to prevent collapsing into a great void is likely around 2.3 times the mass of our Sun. This limit implies that lots of binary neutron star mergers go on to form more massive neutron star residues which survive for at least some time if appropriate. Understanding how these items progress and act will supply a myriad of insights into the behavior of nuclear matter and the afterlives of stars more enormous than our Sun.
Recommendation: “The evolution of binary neutron star post-merger residues: an evaluation” by Nikhil Sarin and Paul D. Lasky, June 2021, General Relativity and Gravitation.DOI: 10.1007/ s10714-021-02831-1.
Written by PhD student Nikhil Sarin, University of Adelaide.
Schematic representation of binary neutron star merger outcomes. Panels A and B: Two neutron stars merge as the emission of gravitational waves drives them towards one another. C: If the residue mass is above a certain mass, it instantly forms a black hole. D: Alternatively, it forms a quasistable hypermassive neutron star. E: As the hypermassive star spins down and cools it can not support itself versus gravitational collapse and collapses into a black hole. F, G: If the remnants mass is sufficiently low, it will endure for longer, as a supramassive neutron star, supported versus collapse through extra assistance versus gravity through rotation, collapsing into a great void once it loses this assistance. H: If the remnant is born with little sufficient mass, it will survive forever as a neutron star. Schematic from Sarin & & Lasky 2021. Credit: Carl Knox (Swinburne University).
On August 17th, 2017, LIGO spotted gravitational waves from the merger of 2 neutron stars. This merger radiated energy across the electro-magnetic spectrum, light that we can still observe today. Neutron stars are extremely dense items with masses bigger than our Sun confined to the size of a little city. These extreme conditions make some consider neutron stars the caviar of astrophysical objects, allowing scientists to study gravity and matter in conditions unlike any other in the Universe.
The momentous 2017 discovery linked a number of pieces of the puzzle on what occurs during and after the merger. However, one piece remains evasive: What remains behind after the merger?
In a current post released in General Relativity and Gravitation, Nikhil Sarin and Paul Lasky, two OzGrav researchers from Monash University, evaluation our understanding of the aftermath of binary neutron star mergers. In particular, they analyze the various results and their observational signatures.
The fate of a residue is determined by the mass of the 2 combining neutron stars and the maximum mass a neutron star can support before it collapses to form a black hole. If the residues mass is smaller sized than this mass limit, then the residue is a neutron star that will live indefinitely, producing electromagnetic and gravitational-wave radiation. If the remnant is more huge than the maximum mass threshold, there are two possibilities: if the residue mass is up to 20% more than the optimum mass limit, it survives as a neutron star for hundreds to thousands of seconds prior to collapsing into a black hole. Observations of other neutron stars in our Galaxy and a number of restraints on the behavior of nuclear matter recommend that the maximum mass threshold for a neutron star to avoid collapsing into a black hole is likely around 2.3 times the mass of our Sun. If correct, this limit implies that lots of binary neutron star mergers go on to form more huge neutron star remnants which endure for at least some time.
