Multiwavelength Emission for a Postmerger Magnetar: The Magnetar-driven Poynting Jet and Its Associated Pulsar Wind Nebula

This is the authors' abstract. We don't add key points for this paper.

A newly born, rapidly rotating magnetar may form in a binary neutron star merger and drive a Poynting flux-dominated relativistic jet. As the jet propagates outward, a forward shock (FS) and a reverse shock (RS) are formed, inflating a pulsar wind nebula (PWN) between them. We present a systematic study of the emission from both the PWN and the jet, whose magnetic energy is subject to dissipation. By following the dynamics of the jet–ejecta–PWN system, we find that, in most cases, the RS is long-lived: it first lags behind the contact discontinuity (CD) and eventually coincides with both the CD and the FS after the jet breakout into the external medium. As a result, the emission exhibits a characteristic temporal evolution. Depending on the optical depth, the emission is initially dominated by thermal radiation from the optically thick ejecta, then by a jet-powered X-ray plateau once the system becomes optically thin, and finally by synchrotron and inverse-Compton radiation from the PWN FS at late times. In particular, external inverse-Compton scattering of jet photons by the FS naturally produces a late-time GeV bump together with a substantial TeV component. Our model can simultaneously account for early thermal emission, X-ray plateaus, and late-time GeV excesses in merger-driven gamma-ray bursts, and also indicates that postmerger magnetar-driven PWNs are potential TeV photon sources.