Speaker
Description
The detail of the particle acceleration at trans-relativistic shocks is still under debate. We propose a way to probe the particle acceleration at trans-relativistic shocks with observations of gamma-ray burst (GRB) afterglows. In the afterglow phase, the shock wave launched in a GRB is gradually decelerated from the relativistic to non-relativistic regimes by sweeping up the ambient interstellar matter. If the electron power-law index depends on the shock Lorentz factor, it is reflected to the evolution of the afterglow spectrum.
We theoretically study the time evolution of the electron power-law index imprinted in GRB afterglow spectra. We introduce a particle acceleration model by a trans-relativistic shock into the standard GRB afterglow model and apply the formulation to structured jet models that are consistent with GRB 170817A, which is the counterpart of the neutron-star merger detected by the gravitational wave signal, GW170817.
As a result, we find that it is possible to observe the transition of the electron acceleration from the relativistic phase to the non-relativistic phase in the evolution of the afterglow spectrum, if GRBs similar to GRB 170817A take place in a dense environment at 200 Mpc.
The detection number of short GRBs will increase in the era of the multi-messenger astronomy including gravitational waves. Thus, we expect that future GRBs can give a constraint on particle acceleration models as proposed in our study. In the presentation, we will discuss the detail of our model and results.
Keywords
GRB afterglows; Particle acceleration; Multiband spectrum; Multi-messenger including gravitational wave signals
| Subcategory | Theoretical Results |
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