The Massive Neutron Star or Low-Mass Black Hole in 2S 0921-630
The Massive Neutron Star or Low-Mass Black Hole in 2S 0921-630
We report on the optical spectroscopy of the eclipsing halo low-mass X-ray binary 2S 0921-630, which reveals the absorption-line radial velocity curve of the K0 III secondary star with a semiamplitude K2 = 92.89 ± 3.84 km s-1, a systemic velocity γ = 34.9 ± 3.3 km s-1, and an …