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 high energy GeV emission of gamma-ray bursts (GRBs), detected by\emph{Fermi}/LAT, has a significantly different morphology compared to thelower energy MeV emission, detected by \emph{Fermi}/GBM. Though the late timeGeV emission is believed to be synchrotron radiation produced via an externalshock, this emission as early as the prompt phase is puzzling. Meaningfulconnection between these two emissions can be drawn only by an accuratedescription of the prompt MeV spectrum. We perform a time-resolved spectroscopyof the GBM data of long GRBs having significant GeV emission, using a modelconsisting of 2 blackbodies and a power-law. We examine in detail the evolutionof the spectral components and found that GRBs having high GeV emission (GRB090902B and GRB 090926A) have a delayed onset of the power-law component, inthe GBM spectrum, which lingers at the later part of the prompt emission. Thisbehaviour mimics the flux evolution in LAT. In contrast, bright GBM GRBs withan order of magnitude lower GeV emission (GRB 100724B and GRB 091003) show acoupled variability of the total and the power-law flux. Further, by analyzingthe data for a set of 17 GRBs, we find a strong correlation between thepower-law fluence in the MeV and the LAT fluence (Pearson correlation: r=0.88and Spearman correlation: $\rho=0.81$). We demonstrate that this correlation isnot influenced by the correlation between the total and the power-law fluencesat a confidence level of 2.3$\sigma$. We speculate the possible radiationmechanisms responsible for the correlation.

A lingering non-thermal component in the GRB prompt emission: predicting GeV emission from the MeV spectrum