Low-efficiency long gamma-ray bursts: a case study with AT2020blt

Sarin, N, Hamburg, R, Burns, E, Ashton, G, Lasky, PD and Lamb, GP ORCID: 0000-0001-5169-4143 (2022) Low-efficiency long gamma-ray bursts: a case study with AT2020blt. Monthly Notices of the Royal Astronomical Society, 512 (1). pp. 1391-1399. ISSN 0035-8711

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Abstract

The Zwicky Transient Facility recently announced the detection of an optical transient AT2020blt at redshift z = 2.9, 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 Fermi data for prompt emission, setting deeper upper limits on the prompt emission than in the original detection paper. Together with KONUS-Wind observations, we show that the gamma-ray efficiency of AT2020blt is 0.3-4.5. 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.

Item Type:	Article
Uncontrolled Keywords:	0201 Astronomical and Space Sciences; Astronomy & Astrophysics
Subjects:	Q Science > QB Astronomy Q Science > QC Physics
Divisions:	Astrophysics Research Institute
Publisher:	Oxford University Press (OUP)
Date of acceptance:	2 March 2023
Date of first compliant Open Access:	15 June 2023
Date Deposited:	15 Jun 2023 11:31
Last Modified:	04 Jul 2025 18:30
DOI or ID number:	10.1093/mnras/stac601
URI:	https://researchonline.ljmu.ac.uk/id/eprint/19843

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