Detection of a compact X-ray source in the supernova remnant G29.6+0.1: A variable anomalous X-ray pulsar?

We present follow-up observations of the serendipitously discovered 7 s X-r ay pulsar AX J1845-0258, which displays characteristics similar to those ob served in the anomalous X-ray pulsars (AXPs). We find a dramatic reduction in its 3-10 keV flux in both new ASCA and Rossi X-Ray Timing Explorer data sets. Within the pulsar's position error locus, we find a faint point sourc e, AX J184453-025640, surrounded by an are of diffuse X-ray emission. This are is coincident with the southeast quadrant of the radio shell of the new ly discovered supernova remnant G29.6+/-0.1, recently reported by Gaensler et al. Lack of sufficient flux from the source prevents us from confirming the 7 s pulsed emission observed in the bright state; hence, at present we cannot definitively resolve whether AX J1845-0258 and AX J184453-025640 are one and the same. If they are the same, then the peak-to-peak luminosity c hanges recorded for AX J1845-0258 may be larger than seen in other AXPs; cl oser monitoring of this pulsar might lead to a resolution on the mechanism that drives AXPs.