Skip to main content
Article thumbnail
Location of Repository

The nature of the late achromatic bump in GRB 120326A

By A. Melandri, F.J. Virgili, C. Guidorzi, M.G. Bernardini, S. Kobayashi, C.G. Mundell, A. Gomboc, B. Dintinjana, V.-P. Hentunen, J. Japelj, D. Kopač, D. Kuroda, A.N. Morgan, I.A. Steele, U. Quadri, G. Arici, D. Arnold, R. Girelli, H. Hanayama, N. Kawai, H. Mikuž, M. Nissinen, T. Salmi, R.J. Smith, L. Strabla, M. Tonincelli and A. Quadri


The long Swift gamma-ray burst GRB120326A at redshift z = 1.798 exhibited a multi-band light-curve with a striking feature: a latetime, long-lasting achromatic rebrightening that is rarely seen in such events. Peaking in optical and X-ray bands ~35 ks (~12.5 ks in the GRB rest frame) after the 70 s GRB prompt burst, the feature brightened nearly two orders of magnitude above the underlying optical power-law decay. By modelling the multi-wavelength light-curves, we investigated possible causes of the rebrightening in the context of the standard fireball model. We excluded a range of scenarios for the origin of this feature: reverse-shock flash, late-time forward-shock peak caused by the passage of the brightest synchrotron frequency through the optical band, late central engine optical or X-ray flares, interaction between the expanding blast wave and a density enhancement in the circumburst medium, and gravitational microlensing. Instead we conclude that the achromatic rebrightening may be caused by a refreshed forward shock or a geometrical effect. In addition, we identify an additional component after the end of the prompt emission, which shapes the observed X-ray and optical light-curves differently, and which rules out a single overall emission component to explain the observed early-time emission

Year: 2014
DOI identifier: 10.1051/0004-6361
OAI identifier:
Download PDF:
Sorry, we are unable to provide the full text but you may find it at the following location(s):
  • (external link)
  • (external link)
  • Suggested articles

    To submit an update or takedown request for this paper, please submit an Update/Correction/Removal Request.