The early (<1 hr) multi-colour afterglow of GRB 050502a with the 2-m liverpool telescope

C. Guidorzi, A. Monfardini, A. Gomboc, C. G. Mundell, I. A. Steele, D. Carter, M. F. Bode, R. J. Smith, C. J. Mottram, M. J. Burgdorf, N. R. Tanvir, N. Masetti, E. Pian

Research output: Contribution to journalConference article

Abstract

The 2-m robotic Liverpool Telescope automatically discovered the optical afterglow of the INTEGRAL gamma-ray burst GRB 050502a 3 min after the GRB onset. The automatic identification of a bright optical transient of r′ ∼ 15.8 triggered for the first time a multi-colour observation sequence in the BVr′i′ filters during the first hour after a GRB. All the four light curves are fitted by a simple power law with index of 1.2 ± 0.1. We also find evidence for an achromatic bump rising at t ∼ 0.02 days. We investigate different scenarios compatible with the data. We find possible evidence for a uniform circumburst medium with clumps in density, as in the case of GRB 021004. The alternative case of a wind environment cannot be ruled out, although it can hardly account for our observations. The alternative interpretation of the bump, as the result of a refreshed shock, appears to be more problematic, although it cannot be ruled out either.

Original languageEnglish
Pages (from-to)330-334
Number of pages5
JournalChinese Journal of Astronomy and Astrophysics
Volume6
Issue numberSUPPL. 1
DOIs
Publication statusPublished - 1 Jan 2006
Event6th International Workshop on Multifrequency Behaviour of High Energy Cosmic Sources: Frascati Workshop 2005 - Vulcano, Italy
Duration: 23 May 200528 May 2005

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Keywords

  • Gamma-rays: bursts
  • Techniques: photometric

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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