PoS - Proceedings of Science
Volume 461 - High Energy Phenomena in Relativistic Outflows VIII (HEPROVIII) - Posters
Multi-pulse GRB prompt emission via a novel pulse-shape model
G. A*, A. Pe'er", F. Ryde" and H. Dereli-Bégué"
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Pre-published on: May 15, 2024
Published on:
The light curves of the prompt phase of gamma-ray bursts (GRBs) exhibit erratic and diverse
behaviour, often with multiple pulses. The temporal shape of individual pulses is often modelled
as ‘fast rise exponential decay’ (FRED). Here, we propose a novel fitting function to measure
pulse asymmetry. We perform a time-resolved spectrum analysis on a sample of 75 pulses from
twenty-seven GRBs that the Fermi Gamma-ray Burst Monitor has identified. When multi-pulse
bursts are taken into account, a distinct behaviour becomes evident: the first pulses have the
most symmetric-like lightcurve, while subsequent pulses show an increase in the asymmetry
parameter, leading to a more FRED-like form. Furthermore, we correlate pulse temporal and
spectral shapes after fitting the spectra with the classical “Band" function. A moderate positive
Spearman correlation between pulse asymmetry and the low-energy spectral index $𝛼_{𝑚𝑎𝑥}$ (where
the maximum is taken over all time bins that cover the pulse shape) is identified. An overlapping
emission mechanism is indicated by the fact that $\sim$ 64% of the GRB pulses fall within the limits
of the slow-cooling synchrotron and non-dissipative photospheric emission models. Thus, our
findings offer a compelling hint towards understanding the origin of GRB pulses
DOI: https://doi.org/10.22323/1.461.0054
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