magnetars

Magnetars are a class of isolated neutron stars with magnetic fields on the order of 10^14 to 10^15 gauss, far stronger than those of ordinary radio pulsars. The extreme field stores enough magnetic energy to power observed high-energy emission over timescales longer than the star’s rotational energy would allow. Consequently, magnetar emission is primarily powered by magnetic field decay and stresses in the crust, rather than by rotation.

Magnetars manifest observationally mainly as Soft Gamma Repeaters (SGRs) and Anomalous X-ray Pulsars (AXPs). They typically exhibit spin periods in the range of about 2 to 12 seconds and show rapid spin-down. Quiescent X-ray luminosities reach 10^33–10^35 erg/s, exceeding what could be supplied by their spin-down energy alone. They produce recurrent bursts and rare giant flares, emitting up to 10^44–10^46 ergs in a fraction of a second to minutes.

Magnetars are young neutron stars, often located near supernova remnants in the Milky Way or in nearby galaxies. The magnetic field decay drives persistent X-ray emission and can trigger dramatic outbursts through crustal fractures (starquakes) and magnetospheric reconnection. Over timescales of roughly 10^4–10^5 years, magnetar activity wanes as the field decays.

The magnetar model was proposed in the early 1990s to explain SGRs and AXPs, and has become the leading framework for understanding these objects. They are relatively rare, with only a few dozen confirmed members.