Radio observations of GRB 100418a: Test of an energy injection model explaining long-lasting GRB afterglows
- Shanghai Astronomical Observatory, 80 Nandan Road, Xujiahui, Shanghai 200030 (China)
- National Center for Radio Astrophysics, Tata Institute of Fundamental Research, Pune (India)
- International Centre for Radio Astronomy Research, Curtin University, Bentley 6102, WA (Australia)
- Department of Physics and Astronomy, University of New Mexico, Albuquerque, NM 87131 (United States)
- National Radio Astronomy Observatory, P.O. Box 0, Socorro, NM 87801 (United States)
- CSIRO Astronomy and Space Science, PO Box 76, Epping, NSW (Australia)
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.
- OSTI ID:
- 22348467
- Journal Information:
- Astrophysical Journal, Vol. 779, Issue 2; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
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