Low-efficiency long gamma-ray bursts: a case study with AT2020blt
Low-efficiency long gamma-ray bursts: a case study with AT2020blt
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 per cent . We speculate that AT2020blt and AT2021any belong to the lo w-ef ficiency tail of long gamma-ray b urst distrib utions that are beginning to be readily observed due to the capabilities of ne w observ atories like the Zwicky Transient Facility.
1391-1399
Sarin, N.
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Hamburg, R.
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Burns, E.
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Ashton, G.
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Lasky, P.D.
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Lamb, G.P.
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22 March 2022
Sarin, N.
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Hamburg, R.
b1863881-4357-4959-ba35-ccae799cb6aa
Burns, E.
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Ashton, G.
a8cec4b1-3c98-4b28-af2a-1e37cb3b9f2a
Lasky, P.D.
21c4d51d-89db-4dc1-b5f9-cd9835d54fad
Lamb, G.P.
f7132e72-c5ae-46bb-80f4-12e702a7305d
Sarin, N., Hamburg, R., Burns, E., Ashton, G., Lasky, P.D. and Lamb, G.P.
(2022)
Low-efficiency long gamma-ray bursts: a case study with AT2020blt.
Monthly Notices of the Royal Astronomical Society, 512 (1), .
(doi:10.1093/mnras/stac601).
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 per cent . We speculate that AT2020blt and AT2021any belong to the lo w-ef ficiency tail of long gamma-ray b urst distrib utions that are beginning to be readily observed due to the capabilities of ne w observ atories like the Zwicky Transient Facility.
Text
stac601
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Accepted/In Press date: 2 March 2022
e-pub ahead of print date: 8 March 2022
Published date: 22 March 2022
Identifiers
Local EPrints ID: 511219
URI: http://eprints.soton.ac.uk/id/eprint/511219
ISSN: 0035-8711
PURE UUID: df01576a-8f24-4b30-9ee9-f66d725a9a54
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Date deposited: 08 May 2026 16:36
Last modified: 09 May 2026 02:43
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Contributors
Author:
N. Sarin
Author:
R. Hamburg
Author:
E. Burns
Author:
G. Ashton
Author:
P.D. Lasky
Author:
G.P. Lamb
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