English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

Despite decades of investigations, the physical mechanism that powers thebright prompt $\gamma$-ray emission from gamma-ray bursts (GRBs) is still notidentified. One important observational clue that remains not properlyinterpreted so far is the existence of time lags of broad light curve pulses indifferent energy bands, named "spectral lags". Here we show that thetraditional view invoking the high-latitude emission "curvature effect" of arelativistic jet cannot account for spectral lags. Rather, the observedspectral lags demand the sweep of a spectral peak across the observing energyband in a specific manner. The duration of the broad pulses and inferredtypical Lorentz factor of GRBs require that the emission region is in anoptically thin emission region far from the GRB central engine. We construct asimple physical model invoking synchrotron radiation from a rapidly expandingoutflow. We show that the observed spectral lags appear naturally in our modellight-curves given that (1) the gamma-ray photon spectrum is curved (asobserved), (2) the magnetic field strength in the emitting region decreaseswith radius as the region expands in space, and (3) the emission region itselfundergoes rapid bulk acceleration as the prompt $\gamma$-rays are produced.These requirements are consistent with a Poynting-flux-dominated jet abruptlydissipating magnetic energy at a large distance from the engine.

Towards an understanding of GRB prompt emission mechanism: I. The origin of spectral lags