http://arxiv.org/abs/1903.01107
We report on the timing properties of the `Crab twin’ pulsar PSR~B0540$-$69 measured with X-ray data taken with the Swift telescope over a period of 1100\,days. The braking index of the pulsar was estimated to be $n = 0.03\pm0.013$ in a previous study performed in 2015 with 500-day Swift data. This small value of $n$ is unusual for pulsars, and a comparison to old measurements of $n\approx2.1$ for the same target determined $\sim$10 years ago suggests a dramatic change in the braking index. To confirm the small value and large change of $n$, we used 1100-day Swift observations including the data used for measuring $n=0.03$. In this study we found that the braking index of PSR~B0540$-$69 is $n=0.163\pm0.001$, somewhat larger than $0.03$. Since the measured value of $n$ is still much smaller than $2.1$, we can confirm the dramatic change in the braking index for this pulsar.
M. Kim and H. An
Tue, 5 Mar 19
25/73
Comments: 7 pages, 4 figures, Accepted to JKAS
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