Low-efficiency long gamma-ray bursts: A case study with AT2020blt
arXiv:2106.01556 · doi:10.1093/mnras/stac601
Abstract
The Zwicky Transient Facility recently announced the detection of an optical transient AT2020blt at redshift , consistent with the afterglow of an on-axis gamma-ray burst. However, no prompt emission was observed. We analyse AT2020blt with detailed models, showing the data are best explained as the afterglow of an on-axis long gamma-ray burst, ruling out other hypotheses such as a cocoon and a low-Lorentz factor jet. We search \textit{Fermi} data for prompt emission, setting deeper upper limits on the prompt emission than in the original detection paper. Together with KONUS-\textit{Wind} observations, we show that the gamma-ray efficiency of AT2020blt is . We speculate that AT2020blt and AT2021any belong to the low-efficiency tail of long gamma-ray burst distributions that are beginning to be readily observed due to the capabilities of new observatories like the Zwicky Transient Facility.
arXiv commentPublished in MNRAS. 11 pages, 4 figures
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