Synchrotron emission in GRBs observed by Fermi: Its limitations and the role of the photosphere

Understand

It has been suggested that the prompt emission in gamma-ray bursts consists of several components giving rise to the observed spectral shape.

• Here we examine a sample of the 8 brightest, single pulsed {\it Fermi} bursts whose spectra are modelled by using synchrotron emission as one of the components.
• Five of these bursts require an additional photospheric component (blackbody).
• In particular, we investigate the inferred properties of the jet and the physical requirements set by the observed components for these five bursts, in the context of a baryonic dominated outflow, motivated by the strong photospheric component.