Fallback-driven evolutionary trajectories of supramassive neutron stars toward the neutron star-black hole transition regime — E8 Intelligence Research

Recent gravitational wave (GW) events, such as GW190814 and GW230529, have hinted at the existence of compact objects that fall in the transitional regime between the maximum neutron star mass and the minimum black hole mass. The nature of these compact objects is heavily debated. We investigate a potential formation channel of heavy neutron stars that exceed a mass limit of 2.5M⊙, where fallback accretion induced simultaneous mass growth and spin-up can enable them to remain either temporarily (long enough to emit detectable GW signals) or permanently stable at supramassive levels. An optimistic scenario was modeled using defined initial parameters. Spin evolution and mass growth were calculated by implementing a power-law decay equation and rotational stability criterion based on a spin-dependent maximum mass model. The parameter space included variations in the fallback angular momentum and neutron star mass. Considering both direct fallback and accretion disk formation, Author: Andrew Stewart Caldin, Independent Researcher, UK. Part of the E8 Intelligence Research series. Platform: e8intelligence.com