Chandra observations of the transient 7 s X-ray pulsar AX J1845.0-0258

We present the results of Chandra X-Ray Observatory observations of the transient anomalous X-ray pulsar candidate AXJ1845.0-0258 in apparent quiescence. Within the source's error circle, we find a point source and possible counterpart, which we designate CXOU J184454.6-025653. No coherent pulsations are detected, and no extended emission is seen. The source's spectrum is equally well described by a blackbody model of temperature kT similar to 2.0 keV or a power-law model with photon index Gamma similar to 1.0. This is considerably harder than was seen for AX J1845.0-0258 during its period of brightening in 1993 (kT similar to 0.6 keV) despite being at least similar to 13 times fainter. This behavior is opposite to that observed in the case of the established transient AXP, XTE J1810-197. We therefore explore the possibility that CXOU J184454.6-025653 is an unrelated source and that AX J1845.0-0258 remains undetected since 1993, with a flux 260-430 times fainter than at that epoch. If so, this would represent an unprecedented range of variability in AXPs.