The long-lasting optical afterglow plateau of short burst GRB 130912A

Abstract

The short burst GRB 130912A was detected by Swift, Fermi satellites and several ground-based optical telescopes. Its X-ray light curve decayed with time normally. The optical emission, however, displayed a long term plateau, which is the longest one in current short GRB observations. In this work we examine the physical origin of the X-ray and optical emission of this peculiar event. We find that the canonical forward shock afterglow emission model can account for the X-ray and optical data self-consistently and the energy injection model that has been widely adopted to interpret the shallowly-decaying afterglow emission is not needed. We also find that the burst was born in a very-low density interstellar medium, consistent with the compact object merger model. Significant fractions of the energy of the forward shock have been given to accelerate the non-thermal electrons and amplify the magnetic fields (i.e., ${\epsilon }_{\mathrm{e}}\sim 0.37$ and ${\epsilon }_{\mathrm{B}}\sim 0.16$, respectively), which are much larger than those inferred in most short burst afterglow modeling and can explain why the long-lasting optical afterglow plateau is rare in short GRBs.

5 pages, 2 figures

References in corpus (4)

• Short Duration Gamma-Ray Bursts with Extended Emission from Proto-Magnetar Spin-Down
• X-Ray Flares from Postmerger Millisecond Pulsars
• The X-ray afterglow flat segment in short GRB 051221A: Energy injection from a millisecond magnetar?
• Revisiting the Long/Soft-Short/Hard Classification of Gamma-Ray Bursts in the Fermi Era

Cited by in corpus (3)

• 2900 square degree search for the optical counterpart of short gamma-ray burst GRB 180523B with the Zwicky Transient Facility
• The interpretation of the multi-wavelength afterglow emission of short GRB 140903A
• Binary Neutron Star (BNS) merger: What we learned from relativistic ejecta of GW/GRB~170817A