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Advancing Our Understanding of GRB Jet Physics: Unifying Physically-Motivated and Purely Physical Modeling

Presentation #108.12 in the session Time-domain Astrophysics - Poster Session.

Published onMay 03, 2024
Advancing Our Understanding of GRB Jet Physics: Unifying Physically-Motivated and Purely Physical Modeling

The presence of both thermal and non-thermal emission components in the early explosion of Gamma-Ray Bursts (GRBs) is well-established. These components have been extensively studied across various wavelengths, from gamma rays to optical, using multiple instruments and space observatories. The spectral characteristics align with the theoretical predictions of the Fireball model, wherein a sub-dominant thermal-like component originates from the jet photospheric emission, while a non-thermal component arises from synchrotron emission through electron acceleration within the jetted outflow, facilitated by internal shocks and/or magnetic reconnections. In this presentation, we delve into these emission components, illustrating how a physically-motivated model can track their evolution with fine time-resolved spectroscopy, reaching down to the millisecond timescale. By utilizing this model, we can extract vital properties of the relativistic outflow, including the magnetization, Lorentz factor profile, photospheric radius evolution, injected power evolution, and energy injection radius. These outputs from the physically-motivated model subsequently serve as inputs for a purely physical model, which effectively narrows down the extensive parameter space. This reduction enables the fitting of observed data to comprehensive physical model templates, thus constraining the various microphysical parameters that characterize different aspects of the outflow, jet geometry, circumburst medium, internal shocks, and external shocks. Ultimately, our work establishes GRBs as cosmological standard candles supported by a robust physical framework. These results not only enhance our understanding of GRB jet physics but also contributes to their application as valuable cosmological tools.

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