Measuring timing properties of PSR B0540-69

TL;DR

This study measures the braking index of pulsar PSR B0540-69 over 1100 days, confirming a dramatic change from previous measurements and revealing a small, unusual braking index value.

Contribution

The paper provides new, precise measurements of the pulsar's braking index over an extended period, confirming a significant change from earlier values and improving understanding of pulsar timing behavior.

Findings

Braking index measured as 0.163±0.001 over 1100 days.

Confirmed a dramatic change from previous value of 0.03.

Braking index remains much smaller than typical 2.1 for pulsars.

Abstract

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.