21 Years of Timing PSR B1509−58

We present an updated timing solution for the young, energetic pulsar PSR B1509-58 based on 21.3 yr of radio timing data and 7.6 yr of X-ray timing data. No glitches have occurred in this time span, in contrast to other well-studied young pulsars, which show frequent glitches. We report a measurement of the third frequency derivative of = (-1.28 ± 0.21) × 10 -31 s -4 . This value is 1.65 σ from (i.e., consistent with) that predicted by the simple constant magnetic dipole model of pulsar spin-down. We measured the braking index to be n = 2.839 ± 0.003 and show that it varies by 1.5% over 21.3 yr owing to contamination from timing noise. Results of a low-resolution power spectral analysis of the significant noise apparent in the data yield a spectral index of α = -4.6 ± 1.0 for the red-noise component.