Revisiting the emission from relativistic blastwaves in a density-jump medium
2014-09-28 Re-brightening bumps are frequently observed in gamma-ray burst afterglows. Many scenarios have been proposed to interpret the origin of these bumps, of which a blast wave encountering a density-jump in the circum-burst environment has been questioned by recent works. The interaction of the blast wave with the high-density medium is ascribed to two shocks: a reverse shock that propagates into the hot shell and a forward shock that propagates into the high-density medium. Thus the system consists of four separated regions: (1) unshocked high-density medium, (2) forward-shocked high-density medium, (3) reverse-shocked hot shell, and (4) unshocked hot shell. In this paper, the quantities (Lorentz factor, density, mass, internal energy, and pressure) of region “i” (regions 2, 3, and 4) are denoted by subscripts “i”, respectively.
By with for WU Xuefeng
Fig. 1.| Afterglow light curves for the four cases (e.g., ?10a100 corresponds to the case that when the blastwave encounters the density jump, the Lorentz factor of the blastwave is 10 and the density ratio is 100). The red lines and black lines are the optical band (4×10^14 Hz) andX-ray band (0.3 keV) light curves, respectively. The dotted lines (Opt-4 or Xray-4) represent the flux density of region 2 before the density-jump and the flux density of region 4 after the jump. The dashed lines (Opt-3 or Xray-3) are the contribution from region 3 after the density-jump. The dash-dotted lines (Opt-2 or Xray-2) mark the flux density of region 2 after the jump, and the solid lines (Opt-tot or Xray-tot) show the total flux density of all the components. A redshift z = 1 has been assumed.