What powers Anomalous X-ray Pulsars and Soft Gamma-ray Repeaters?

Anomalous X-ray Pulsars (AXPs) and Soft Gamma-ray Repeaters (SGRs) are young, isolated neutron stars, which emit bright bursts of hard X-rays and, more rarely, exceptionally energetic giant flares. They are believed to have strong external magnetic fields of the order of 1014 – 1015G, reaching even higher values in their interior, and are known as magnetars. In this picture, both the steady-state X-ray flux and the emission of bursts/flares are thought to be powered by the reservoir of magnetic energy stored in the star’s interior. 
Alternative explanations, including accretion of matter onto a neutron star with normal dipole magnetic field (1012 – 1013 G) have also been proposed. They can explain naturally not only the steady-state luminosity and the energy spectra of AXPs and SGRs, but also the energy-dependent pulse profiles. The accreting matter comes from a fallback disk around the neutron star. In the accretion picture the bursts are explained as coming from strong multipole fields.

This Special Session fills three 1.5-hour blocks. We will have four invited talks (of half an hour each): one on observations of AXPs and SGRs, one on the magnetar model, one on the accretion model and, at the end of the Special Session, one on summary and conclusions. The rest of the time (two and a half hours) will be given to ten contributed talks (of 15 minutes each). Additional contributions will be presented as posters.

Programme

  • Observations of AXPs and SGRs
  • Modeling of persistent and bursting emission from AXPs and SGRs
  • Formation and evolution of AXPs and SGRs
  • Low magnetic field magnetars
  • High magnetic field radio pulsars