Establish the long-term fate of the enhanced PWN luminosity

Determine whether the elevated X-ray luminosity of the PSR B0540--69 pulsar wind nebula eventually decays as the pulsar's braking index recovers toward its pre-transition value.

Background

The X-ray luminosity of the PSR B0540--69 pulsar-plus-nebula system increased after the 2011 spin-down-rate transition, and the enhanced state persisted for more than 14 years. Meanwhile, the braking index has continued to recover but has not returned to its pre-transition value. Continued monitoring is therefore needed to resolve whether the nebular brightening is a persistent state or will eventually decline in association with the timing recovery.

References

Continued EP/FXT and multi-wavelength monitoring will be crucial for determining whether the elevated X-ray luminosity eventually decays as the braking index recovers, for detecting possible responses to future rotational instabilities, and for constraining how the additional spin-down power is partitioned between particles, magnetic field, and radiation within the PWN.

— Flux Evolution of PSR B0540--69 and the Spectral Energy Distribution of its Pulsar Wind Nebula  (2610.13182 - Zhang et al., 9 Oct 2026) in Section 6, Conclusion and Discussion