Correlated Infrared and X-Ray Flux Changes Following the 2002 June Outburst of the Anomalous X-Ray Pulsar 1E 2259+586

Abstract

We present the results of anear-infrared monitoring program of the anomalous X-ray pulsar 1E2259+586, performed at the Gemini Observatory. This program began 3 daysafter the pulsar's 2002 June outburst and spans ~1.5 yr. We findthat after an initial increase associated with the outburst, thenear-infrared flux decreased continually and reached the preburstquiescent level after about 1 yr. We compare both the near-infraredflux enhancement and its decay to those of the X-ray afterglow andfind them to be remarkably consistent. Fitting simple power lawsto the Rossi X-Ray Timing Explorer pulsed flux and near-infrareddata for t>1 day postburst, we find the following decay indices:alpha=-0.21+/-0.01 (X-ray) and alpha=-0.21+/-0.02 (near-infrared), where fluxis a function of time such that F~t alpha. This suggeststhat the enhanced infrared and X-ray fluxes have a physical linkpostoutburst, most likely from the neutron star magnetosphere.