anomalous X-ray pulsar
An anomalous X-ray pulsar (AXP) is a type of X-ray pulsar with a very long axial rotation period (for a pulsar), of 6 to 12 seconds, combined with a very powerful X-ray emission that cannot be explained by such a low spin rate. Two main theories exist to explain the anomalously powerful X-rays. In the first model, bits of gas blown off in the supernova explosion that created the pulsar fall back onto the remnant star, whose magnetic field is assumed to be no stronger than an ordinary pulsar's. As the gas collects on the surface, it becomes hot and emits X-rays. In the second model, which is now strongly supported by observation, AXPs are assumed to be magnetars – neutron stars with ultra-strong magnetic fields.