Giant partner star may be necessary to form magnetar

Science : Magnetars are an unusual class of pulsars that have magnetic fields 100 trillion times as strong as Earth’s. To try to understand how magnetars form, Simon Clark of the Open University in Milton Keynes, UK, and his colleagues examined a star cluster that is home to a known magnetar and found a blue supergiant star they think was at one time its partner. Because the blue supergiant is rapidly moving away from the cluster, it was likely propelled by the explosion of another star. The supergiant also has unusual proportions of carbon, nitrogen, and oxygen . To explain the elemental imbalance, Clark’s team hypothesizes that if the blue supergiant had been the premagnetar star’s binary partner, it could have lost gas to the premagnetar, which could have increased the premagnetar’s rotation and magnetic field. Then, as the premagnetar aged and expanded, the blue supergiant could have stolen gas that was high in carbon. The loss of gas would have reduced the mass of the premagnetar, speeding its rotation even further before it went supernova.