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Title: Radio observations of GRB 100418a: Test of an energy injection model explaining long-lasting GRB afterglows

We present the results of our radio observational campaign of gamma-ray burst (GRB) 100418a, for which we used the Australia Telescope Compact Array, the Very Large Array, and the Very Long Baseline Array. GRB 100418a was a peculiar GRB with unusual X-ray and optical afterglow profiles featuring a plateau phase with a very shallow rise. This observed plateau phase was believed to be due to a continued energy injection mechanism that powered the forward shock, giving rise to an unusual and long-lasting afterglow. The radio afterglow of GRB 100418a was detectable several weeks after the prompt emission. We conducted long-term monitoring observations of the afterglow and attempted to test the energy injection model advocating that the continuous energy injection is due to shells of material moving at a wide range of Lorentz factors. We obtained an upper limit of γ < 7 for the expansion rate of the GRB 100418a radio afterglow, indicating that the range-of-Lorentz factor model could only be applicable for relatively slow-moving ejecta. A preferred explanation could be that continued activity of the central engine may have powered the long-lasting afterglow.
Authors:
;  [1] ;  [2] ; ; ;  [3] ;  [4] ;  [5] ;  [6]
  1. Shanghai Astronomical Observatory, 80 Nandan Road, Xujiahui, Shanghai 200030 (China)
  2. National Center for Radio Astrophysics, Tata Institute of Fundamental Research, Pune (India)
  3. International Centre for Radio Astronomy Research, Curtin University, Bentley 6102, WA (Australia)
  4. Department of Physics and Astronomy, University of New Mexico, Albuquerque, NM 87131 (United States)
  5. National Radio Astronomy Observatory, P.O. Box 0, Socorro, NM 87801 (United States)
  6. CSIRO Astronomy and Space Science, PO Box 76, Epping, NSW (Australia)
Publication Date:
OSTI Identifier:
22348467
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 779; Journal Issue: 2; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; AFTERGLOW; COSMIC GAMMA BURSTS; EMISSION; EXPANSION; INJECTION; RELATIVISTIC RANGE; TELESCOPES; X RADIATION