Abstract
ABSTRACT We present the results of radio observations from the eMERLIN telescope combined with X-ray data from Swift for the short-duration gamma-ray burst (GRB) 200826A, located at a redshift of 0.71. The radio light curve shows evidence of a sharp rise, a peak around 4–5 d post-burst, followed by a relatively steep decline. We provide two possible interpretations based on the time at which the light curve reached its peak. (1) If the light curve peaks earlier, the peak is produced by the synchrotron self-absorption frequency moving through the radio band, resulting from the forward shock propagating into a wind medium and (2) if the light curve peaks later, the turnover in the light curve is caused by a jet break. In the former case we find a minimum equipartition energy of ∼3 × 1047 erg and bulk Lorentz factor of ∼5, while in the latter case we estimate the jet opening angle of ∼9–16°. Due to the lack of data, it is impossible to determine which is the correct interpretation, however due to its relative simplicity and consistency with other multiwavelength observations which hint at the possibility that GRB 200826A is in fact a long GRB, we prefer the scenario one over scenario two.
Highlights
Gamma-ray bursts (GRBs) are flashes of gamma-rays that are thought to be produced from internal shocks during the launch of ultrarelativistic jets (Eichler et al 1989; Narayan, Paczynski & Piran 1992; Kobayashi, Piran & Sari 1997)
This lends itself to the possibility that the light curve could be fit with a broken power law, an f-test performed on the data set allows us to reject a broken power law in favour of a single power-law fit (Evans et al 2009)
We have reported on radio observations of GRB 200826A performed with Element Remotely Linked Interferometer Network (eMERLIN) at 5 GHz lasting from 4 to 11 d after the burst
Summary
Gamma-ray bursts (GRBs) are flashes of gamma-rays that are thought to be produced from internal shocks during the launch of ultrarelativistic jets (Eichler et al 1989; Narayan, Paczynski & Piran 1992; Kobayashi, Piran & Sari 1997). They can last from tens of milliseconds to thousands of seconds, and large samples of GRBs show a bimodality in their duration as a result of different progenitor systems (Kouveliotou et al 1993).
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