A Phase-connected Timing Solution for the Magnetar Candidate 1E 1841−045

We report on a long-term monitoring campaign of 1E 1841-045, the 12 s anomalous X-ray pulsar and magnetar candidate at the center of the supernova remnant Kes 73. We have obtained approximately monthly observations of the pulsar with the Rossi X-Ray Timing Explorer ( RXTE ) spanning over 2 years, during which time 1E 1841-045 is found to be rotating with sufficient stability to derive a phase-connected timing solution. A linear ephemeris is consistent with measurements of the pulse period made over the last 15 years with the Ginga , ASCA , RXTE , and BeppoSAX observatories. Phase residuals suggest the presence of "timing noise," as is typically observed from young radio pulsars. These results confirm a rapid, constant spin-down for the pulsar, which continues to maintain a steady flux; this is inconsistent with most accretion scenarios.