Diverse Features of the Multiwavelength Afterglows of Gamma-Ray Bursts: Natural or Special?

Figure 1

Evolution of the Lorentz factors of different regions when there is a density jump [47]. Two cases are calculated: one corresponds to the density jump ratio of 10 (a), and the other corresponds to the jump ratio 100 (b). The vertical dashed line marks the time of encountering the density jump. The green solid lines represent before encountering the density jump and during the encountering, both denoted by . The blue solid lines and red solid lines represent (or , ) and the thermal Lorentz factor of the baryons in Region 3 () after the encountering, respectively. The horizontal dashed lines mark the values of corresponding Lorentz factors (which remain constant during the reverse shock crossing time) given by [57]. Note that (see the green solid lines) during the encounter is almost constant (slowly increasing due to adiabatic expansion), which is shown as a “plateau” that is significantly shorter than that of . The shortness of the “plateau” of is due to the different transformation formula between the burst frame time and the apparent time in the observer frame.

(a)

(b)