Slowly rotating Red Giant star has same angular momentum as tiny, fast rotating neutron star. Rotating neutron star only thing that could create that frequency of pulses. If the beam sweeps past Earth, we see a flash of light. Spin rate suddenly increases to conserve angular momentum. See glitch in pulse rate.
Gravity finally wins, compressing core to mathematical point at center.
Formed in supernova explosion. Use Einstein's General Relativity to describe gravitational effects. Use Kepler's 3rd law to find sum of masses. Friction increases inward causing increasing temperature as approach the event horizon-produce wide spectrum of radiation.