Back to Quiescence: Postoutburst Evolution of the Pulsar J1119–6127 and Its Wind Nebula

Abstract

Abstract We report on the analysis of a deep Chandra observation of the high-magnetic-field pulsar (PSR) J1119–6127 and its compact pulsar wind nebula (PWN) taken in 2019 October, three years after the source went into outburst. The 0.5–7 keV postoutburst (2019) spectrum of the pulsar is best described by a two-component blackbody plus power-law model with a temperature of 0.2 ± 0.1 keV, photon index Γ = 1.8 ± 0.4, and X-ray luminosity of 1.9 − 0.3 + 0.3 × 1033 erg s−1, consistent with its preburst quiescent phase. We find that the pulsar has gone back to quiescence. The compact nebula shows a jet-like morphology elongated in the north–south direction, similar to the preburst phase. The postoutburst PWN spectrum is best fit by an absorbed power law with a photon index Γ = 2.3 ± 0.5 and a flux of 3.2 − 0.2 + 0.3 ×10−14 erg cm−2 s−1 (0.5–7 keV). The PWN spectrum shows evidence of spectral softening in the postoutburst phase, with the preburst photon index Γ = 1.2 ± 0.4 changing to Γ = 2.3 ± 0.5 and the preburst luminosity of 1.5 − 0.2 + 0.3 × 1032 erg s−1 changing to 2.7 − 0.2 + 0.3 × 1032 erg s−1 in the 0.5–7 keV band, suggesting magnetar outbursts can impact PWNe. The observed timescale for returning to quiescence, of just a few years, implies a rather fast cooling process and favors a scenario where J1119 is temporarily powered by magnetic energy following the magnetar outburst, in addition to its spin-down energy.