The enigmatic spin evolution of PSR J0537-6910: r-modes, gravitational waves and the case for continued timing

Understand

We discuss the unique spin evolution of the young X-ray pulsar PSR J0537-6910, a system in which the regular spin down is interrupted by glitches every few months.

• Drawing on the complete timing data from the Rossi X-ray Timing Explorer (RXTE, from 1999-2011), we argue that a trend in the inter-glitch behaviour points to an effective braking index close to $n=7$, much larger than expected.
• This value is interesting because it would accord with the neutron star spinning down due to gravitational waves from an unstable r-mode.
• We discuss to what extent this, admittedly speculative, scenario may be consistent and if the associated gravitational-wave signal would be within reach of ground based detectors.