Radio Shell G327.24-0.13 around Magnetar 1E 1547.0-5408: Supernova Remnant or Stellar Wind Bubble?

Determining why some supernova produce radio pulsars and others magnetars, neutron stars with surface magnetic fields >100x stronger than those of normal radio pulsars, requires determining the properties of the progenitor star and supernova of magnetars. To do this for magnetar 1E 1547.0-5408, we wish to determine if the radio shell surrounding this neutron star is a stellar wind bubble or a supernova remnant. In the former, we will be able to estimate the mass of the progenitor star, in the latter, the explosion energy of progenitor explosion. We will also determine if the radio spectrum of this magnetar has changed since 2007, a period in which its radio flux has decreased significantly.