1999A&A...346..929I

The 8.7s X-ray pulsar 4U 0142+61 was monitored by BeppoSAX between January 1997 and February 1998. This source belongs to the rapidly growing class of ``anomalous" X-ray pulsars (AXPs) which have pulse periods in the 6-12s range and no plausible optical, infrared or radio counterparts. The BeppoSAX periods measurements show that 4U 0142+61 continues its spin-down at a nearly constant rate of {dot}(P)∼2x10^–12s/s. The 0.5-10keV pulse shape is double peaked. The phase-averaged spectrum can be described by a steep absorbed power-law (Γ∼4) plus a blackbody with kT∼0.4keV. 4U 0142+61 was also detected serendipitously in a March 1996 RXTE observation pointed towards the nearby 1455s X-ray pulsar RX J0146.9+6121. The timing analysis results are reported for this observation and the spin history of 4U 0142+61 since 1979 is discussed.