Peculiar Spin Frequency and Radio Profile Evolution of PSR J1119$-$6127 Following Magnetar-like X-ray Bursts

TL;DR

This paper studies the unusual spin frequency and radio profile changes of PSR J1119-6127 after magnetar-like X-ray bursts, revealing correlated evolution of spin-down rate, pulse profile, and flux density, linked to magnetic field reconfiguration.

Contribution

It provides the first detailed observation of the correlated evolution of spin, radio flux, and profile in a high magnetic-field pulsar after magnetar-like bursts, suggesting magnetic reconfiguration or particle winds as causes.

Findings

Net spin-down of Δν ≈ -4×10^{-4} Hz after bursts

Radio pulsations disappeared then reappeared with increased flux

Pulse profile and polarization showed dramatic, short-term changes

Abstract

We present the spin frequency and profile evolution of the radio pulsar J1119$-$6127 following magnetar-like X-ray bursts from the system in 2016 July. Using data from the Parkes radio telescope, we observe a smooth and fast spin-down process subsequent to the X-ray bursts resulting in a net change in the pulsar rotational frequency of $\Delta\nu\approx-4\times10^{-4}$\,Hz. During the transition, a net spin-down rate increase of $\Delta\dot\nu\approx-1\times10^{-10}$\,Hz\,s$^{-1}$ is observed, followed by a return of $\dot{\nu}$ to its original value. In addition, the radio pulsations disappeared after the X-ray bursts and reappeared about two weeks later with the flux density at 1.4\,GHz increased by a factor of five. The flux density then decreased and undershot the normal flux density followed by a slow recovery back to normal. The pulsar's integrated profile underwent dramatic and short-term changes in total intensity, polarization and position angle. Despite the complex evolution, we observe correlations between the spin-down rate, pulse profile shape and radio flux density. Strong single pulses have been detected after the X-ray bursts with their energy distributions evolving with time. The peculiar but smooth spin frequency evolution of PSR~J1119$-$6127 accompanied by systematic pulse profile and flux density changes are most likely to be a result of either reconfiguration of the surface magnetic fields or particle winds triggered by the X-ray bursts. The recovery of spin-down rate and pulse profile to normal provides us the best case to study the connection between high magnetic-field pulsars and magnetars.