We investigate the spin evolution of the binary X-ray pulsar 2S 0114+650, which possesses the slowest known spin period of $\sim 2.7$ hours. We argue that, to interpret such long spin period, the magnetic field strength of this pulsar must be initially $\gsim 10^{ 14}$ G, that is, it was born as a magnetar. Since the pulsar currently has a normal magnetic field $\sim 10^{ 12}$ G, our results present support for magnetic field decay predicted by the magnetar model.
Categories: astro-ph