Observations of the Optical Afterglow of GRB 050319 : Wind to ISM transition in view

Abstract

The collapse of a massive star is believed to be the most probable progenitor of a long GRB. Such a star is expected to modify its environment by stellar wind. The effect of such a circum-stellar wind medium is expected to be seen in the evolution of a GRB afterglow, but has so far not been conclusively found. We claim that a signature of wind to constant density medium transition of circum-burst medium is visible in the afterglow of GRB 050319. Along with the optical observations of the afterglow of GRB 050319 we present a model for the multiband afterglow of GRB 050319. We show that the break seen in optical light curve at $\sim$ 0.02 day could be explained as being due to wind to constant density medium transition of circum-burst medium, in which case, to our knowledge, this could be the first ever detection of such a transition at any given frequency band. Detection of such a transition could also serve as a confirmation of massive star collapse scenario for GRB progenitors, independent of supernova signatures.

11 pages, 3 tables, 1 figures

References in corpus (4)

• Forming a constant density medium close to long gamma-ray bursts
• Multi-color Shallow Decay and Chromatic Breaks in the GRB 050319 Optical Afterglow
• Optical observations of GRB 060124 afterglow: A case for an injection break
• Asymmetric Wolf-Rayet winds: implications for GRB afterglows

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