SpitzerMid‐Infrared Upper Limits on Anomalous X‐Ray Pulsars 1E 1048.1−5937, 1RXS J170849.0−400910, and XTE J1810−197

We report on mid-infrared imaging observations of the anomalous X-ray pulsars(AXPs) 1E 1048.1-5937, 1RXS J170849-400910, and XTE J1810-197. The observationswere carried out at 4.5 and 8.0 microns with the Infrared Array Camera and at24 microns with the Multiband Imaging Photometer on the Spitzer SpaceTelescope. No mid-infrared counterparts were detected. As infrared emissionfrom AXPs may be related to their X-ray emission either via the magnetosphereor via a dust disk, we compare the derived upper limits on the infrared/X-rayflux ratios of the AXPs to the same ratio for 4U 0142+61, an AXP previouslydetected in the mid-infrared range. The comparison indicates that our threenon-detections are consistent with their relatively low X-ray fluxes. For XTEJ1810-197, our upper limits set a constraint on its rising radio/millimeterenergy spectrum, suggesting a spectral break between 1.5$\times10^{11}$--6$\times10^{13}$ Hz.Comment: 6 pages, 5 figures, ApJ, accepte