We report the discovery of a 4.5 \mu \mbox { { m } } counterpart to the anomalous X-ray pulsar ( magnetar ) 1E 2259+586 with the Spitzer Space Telescope .
The mid-infrared flux density is 6.3 \pm 1.0 \mu \mbox { { Jy } } at 4.5 \mu \mbox { { m } } and < 20 \mu \mbox { { Jy } } ( at 95 % confidence ) at 8 \mu \mbox { { m } } , or 0.02 % of the 2–10 keV X-ray flux ( corrected for extinction ) .
Combining our Spitzer measurements with previously published near-infrared data , we show that the overall infrared emission from 1E 2259+586 is qualitatively similar to that from the magnetar 4U 0142+61 .
Therefore , the passive X-ray-heated dust disk model originally developed for 4U 0142+61 might also apply to 1E 2259+586 .
However , the IR data from this source can also be fitted by a simple power-law spectrum as might be expected from magnetospheric emission .