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

The composition of a jet is still an unsolved problem in gamma-ray bursts(GRBs). Several previous studies have suggested that the prompt emissionspectrum of GRBs is likely to consist of a few components that may arise fromdifferent jet compositions. Here we present a systematic analysis to search forthe GRBs that seem to show the transition from a fireball to thePoynting-flux-dominated outflow between well-separated pulses within a singleburst, like the GRB 160626B, using the Gamma-ray Burst Monitor data of the\emph{Fermi} satellite. We obtain 43 GRBs with clear multiple pulses and findthat 9/43 (21\%) bursts may exhibit such a transition based on thetime-integrated spectral analysis. We then select a further four bursts withthe data of adequate quality to perform a detailed time-resolved spectralanalysis, and we find that in three bursts the thermal-like pulse is aprecursor. Furthermore, based on the time-resolved spectra, we constrain theoutflow properties for those thermal pulses and find them consistent with thetypical properties of the photosphere emission. Also, the later pulses with thesofter low-energy spectral index are compatible with the optically thinsynchrotron emission model. Our analysis indicates that a good fraction of themultipulse {\it Fermi} bursts may obtain the transition from fireball to thePoynting-flux-dominated outflow.

MultiPulse {\it Fermi} Gamma-Ray Bursts. I. Evidence of the Transition from Fireball to Poynting-flux-dominated Outflow