After at least 6 years of quiescence , Anomalous X-ray Pulsar ( AXP ) 4U 0142+61 entered an active phase in 2006 March that lasted several months and included six X-ray bursts as well as many changes in the persistent X-ray emission .
The bursts , the first seen from this AXP in > 11 years of Rossi X-ray Timing Explorer monitoring , all occurred in the interval between 2006 April 6 and 2007 February 7 .
The burst durations ranged from 8 - 3 \times 10 ^ { 3 } s. The first five burst spectra are well modeled by blackbodies , with temperatures kT \sim 2 - 6 keV .
However , the sixth burst had a complicated spectrum that is well characterized by a blackbody plus three emission features whose amplitude varied throughout the burst .
The most prominent feature was at 14.0 keV .
Upon entry into the active phase the pulsar showed a significant change in pulse morphology and a likely timing glitch .
The glitch had a total frequency jump of ( 1.9 \pm 0.4 ) \times 10 ^ { -7 } Hz , which recovered with a decay time of 17 \pm 2 days by more than the initial jump , implying a net spin-down of the pulsar .
We discuss these events in the context of the magnetar model .