The Likely Near-Infrared Counterpart to the Anomalous X-Ray Pulsar 1E 1048.1−5937

We report our discovery of the likely near-infrared counterpart to theanomalous X-ray pulsar (AXP) 1E1048.1-5937, using observations from the 6.5-mBaade (Magellan-I) telescope in Chile. We derived a precise position for theX-ray source using archival data from the Chandra X-Ray Observatory. Thisposition is inconsistent with a position reported earlier from XMM-Newton, butwe show that the originally reported XMM-Newton position suffered from attitudereconstruction problems. Only two of the infrared objects in a 17 arcsec x 17arcsec field containing the target have unusual colors, and one of these hascolors consistent with those of the identified counterparts of two other AXPs.The latter object is also the only source detected within the 0.6 arcsecChandra error circle, and we identify it as the counterpart to 1E1048.1-5937.This is the first AXP counterpart detected in multiple infrared bands, withmagnitudes J=21.7(3), H=20.8(3), and K=19.4(3). There is marginal evidence forspectral flattening at longer wavelengths.Comment: 4 pages. Accepted for publication in ApJ Letter