Evidence for free precession in the pulsar B1642-03

We present an analysis of the timing data of the pulsar B1642-03, collected over a span of 30 years between 1969 and 1999. During this interval, the timing residuals exhibit cyclical changes with amplitude varying from 15 to 80 ms and spacing of maxima varying from 3 to 7 yr. Interpretation of these observed cyclical changes in terms of free precession suggests a wobble angle of about 0.degrees8.