With the twelve-year long observations by {\sl Fermi}-LAT, we discover two pairs of spin-down state transitions of PSR J1124--5916, making it the second young pulsar detected to have such behaviors. PSR J1124--5916 shows mainly two states according to its spin-down rate evolution, the normal spin-down state and the low spin-down state. In about 80\% of the observation time, the pulsar is in the normal spin-down state, in which the spin-down rate decreases linearly and gives a braking index of 1.98±0.04. The two transitions to the low spin-down state are in MJD 55183--55803 and MJD 56114--56398 respectively, with fractional amplitudes both ∼0.4%. No significant difference between the γ-ray profiles of the two spin-down states is detected, which is similar to PSR B0540-69, the other young pulsar with state transition detected.
@article{arxiv.2008.03671,
title = {Discovery of state transition behaviors in PSR J1124--5916},
author = {M. Y. Ge and J. P. Yuan and F. J. Lu and H. Tong and S. Q. Zhou and L. L. Yan and L. J. Wang and Y. L. Tuo and X. F. Li and L. M. Song},
journal= {arXiv preprint arXiv:2008.03671},
year = {2020}
}