That work included making the discoveries that both Cen X-3 and Her X-1 are members of close binary systems and their x-rays are fueled by interacting with the atmospheres of their respective companions. In addition, Rich Levinson also discovered that unlike all the other isolated pulsars known at that time that had spin rates that are slowing down, the spin rates of the binary x-ray pulsars have spin rates that are actually speeding up. After 1973, Rich Levinson transitioned his career into software engineering, where he remained until he recently retired and have more time to dedicate to this work on the pulsars.