During 2002–2003 the number of IR-identified counterparts to the Anomalous X-ray Pulsars (AXPs) has grown to four (4U 0142+61, IE 2259+586, IE 1048.1−5937 and RXS J170849−400910) out of the six objects (plus two candidates) known in this class. More importantly, some new common characteristics have been identified, such as IR variability, IR flattening in the broad-band energy spectrum, X-ray spectral variability as a function of pulse phase (which are not predicted by the magnetar model), and X-ray bursts (which cannot be explained in terms of standard accretion models). We present the results obtained from an extensive multi-wavelength observational campaign carried out with the NTT and CFHT for the optical/IR bands, and XMM and Chandra (plus BeppoSAX archival data) in X-rays. Based on these results and those reported in the literature, the IR-to-X-ray emission of AXPs is compared.
Pulse Phase Estimation of X-ray Pulsar with the Aid of Vehicle Orbital Dynamics