The 2016 Outburst of PSR J1119-6127: Cooling and a Spin-down-dominated Glitch

We report on the aftermath of a magnetar outburst from the young, high magnetic field radio pulsar PSR J1119-6127 that occurred on 2016 July 27. We present the results of a monitoring campaign using the Neil Gehrels Swift X-ray Telescope, NuSTAR, and XMM-Newton. After reaching a peak absorbed 0.5-10 keV flux of {45}_-7⁺⁵× {10}^-12 erg cm^-2 s^-1 on 2016 July 27, the pulsar’s X-ray flux declined by factor of ∼50 to {0.83}_-0.06^+0.06× {10}^-12 erg cm^-2 s^-1 on 2016 December 12. The X-ray spectra are well described by a blackbody plus a hard power-law tail. During this time, the blackbody radius decreases monotonically by a factor of ∼4 over a span of nearly 200 days. We also report a highly pulsed hard X-ray emission component, which fades on a similar timescale to the soft X-ray flux, as predicted by models of relaxation of magnetospheric current twists. The previously reported spin-up glitch that accompanied this outburst was followed by a period of enhanced and erratic torque, leading to a net spin down of ∼3.5 × 10^-4 Hz, a factor of ∼24 over-recovery. We suggest that this and other radiatively loud magnetar-type glitch recoveries are dominated by magnetospheric processes, in contrast to conventional radio pulsar glitch recoveries which are dominated by internal physics.