Astronomers identify likely supermassive neutron star in binary system

Discovery of unusual binary pair

To identify this system, researchers analyzed information gathered by the Large Sky Area MultiObject Fiber Spectroscopic Telescope and the Apache Point Observatory Galactic Evolution Experiment. They observed a red giant star interacting with an invisible companion that exerts gravitational effects on its partner. The inferred mass of this unseen object suggests it is likely an unusually massive neutron star pushing known boundaries. This finding was published in Science Advances as part of ongoing studies into stellar remnants.

Mass gap and orbital details

While neutron stars generally possess a mass equal to 1.4 times that of our sun, black holes typically weigh at least five solar masses. The newly discovered object is believed to weigh between 1.8 and 2.8 solar masses, though the most likely figure stands at 2.2 solar masses. Completing one full orbit takes approximately 3.3 years, which suggests that the distance separating these two objects is quite large. Since no light was observed beyond what came from the red giant, the companion cannot be a standard star.

Orbit shape defies simulations

The system follows a surprisingly near-circular path despite its wide separation which is unusual for binary systems with neutron stars. Numerous other massive neutron stars reside in compact binary systems and probably acquired their mass by siphoning matter from companion objects. It seems unlikely that this candidate neutron star will siphon matter from the nearby red giant due to excessive distance. In addition, the researchers ran approximately 300,000 POSYDON simulations of isolated binaries to obtain some understanding of these uncommon arrangements.