The Variable X‐ray and Near‐IR Behavior of the Particularly Anomalous X‐ray Pulsar 1E 1048.1–5937

We present the results of X‐ray and near‐IR observations of the anomalous X‐ray pulsar 1E 1048.1–5937, believed to be a magnetar. This AXP underwent a period of extreme variability during 2001–2004, but subsequently entered an extended and unexpected quiescence in 2004–2006, during which we monitored it with RXTE, CXO, and HST. Its timing properties were stable for >3 years throughout the quiescent period. 1E 1048.1–5937 again went into outburst in March 2007, which saw a factor of >7 total X‐ray flux increase which was anti‐correlated with a pulsed fraction decrease, and correlated with spectral hardening, among other effects. The near‐IR counterpart also brightened following the 2007 event. We discuss our findings in the context of the magnetar and other models.