Magnetar

Magnetars are a type of neutron star characterized by extremely strong magnetic fields, typically about 10^14 to 10^15 gauss. The decay of these fields powers the observable emission, making magnetars distinct from ordinary pulsars whose radiated power is primarily drawn from rotation. Most magnetars are isolated and relatively young, emitting persistent X-ray radiation interspersed with short bursts of soft gamma rays and X-rays.

Magnetars are believed to form from the remnants of massive stars after core-collapse supernovae. Their rotation periods are longer than those of most neutron stars, typically a few seconds (roughly 2 to 12 s), and they spin down over time due to magnetic braking. The decay of the ultra-strong magnetic field heats the neutron star’s crust, producing thermal X-ray emission and powering magnetar activity.

Observationally, magnetars show two related phenomenology: short, repetitive bursts and rare, extremely energetic giant flares. Short bursts last fractions of a second to a few seconds, while giant flares release enormous energies, with an initial hard spike followed by a pulsating tail. The total energy of giant flares is commonly estimated around 10^44 to 10^46 ergs. Spectra are typically modeled with a combination of thermal and non-thermal components.

Magnetars were discovered as soft gamma repeaters and anomalous X-ray pulsars. Notable examples include SGR 1806-20, SGR 1900+14 and AXP 1E 2259+586. Studies across X-ray and infrared wavelengths continue to test magnetar models and their implications for ultra-strong magnetic fields and neutron-star crust physics.

Magnetars provide a natural laboratory for extreme magnetic fields, quantum electrodynamics in strong fields, and the behavior of neutron-star crusts under strain. They help explain high-energy astrophysical transient phenomena and inform studies of stellar evolution and compact objects.