  Magnetars are a special class of slowly rotating neutron stars with extremely
strong magnetic fields -- at least an order of magnitude larger than those of
the "normal" radio pulsars. The potential evolutionary links and differences
between these two types of objects are still unknown; recent studies, however,
have provided circumstantial evidence connecting magnetars with very massive
progenitor stars. Here we report the discovery of an infrared elliptical ring
or shell surrounding the magnetar SGR 1900+14. The appearance and energetics of
the ring are difficult to interpret within the framework of the progenitor's
stellar mass loss or the subsequent evolution of the supernova remnant. We
suggest instead that a dust-free cavity was produced in the magnetar
environment by the giant flare emitted by the source in August 1998.
Considering the total energy released in the flare, the theoretical
dust--destruction radius matches well with the observed dimensions of the ring.
We conclude that SGR 1900+14 is unambiguously associated with a cluster of
massive stars, thereby solidifying the link between magnetars and massive
stars.
