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Li, ML 
ORCID: 0009-0001-6911-9144, Ho, AYQ ORCID: 0000-0002-9017-3567, Ryan, G ORCID: 0000-0001-9068-7157, Perley, DA ORCID: 0000-0001-8472-1996, Lamb, GP ORCID: 0000-0001-5169-4143, A.J., N ORCID: 0000-0002-8070-5400, Andreoni, I ORCID: 0000-0002-8977-1498, Anupama, GC ORCID: 0000-0003-3533-7183, Bellm, EC ORCID: 0000-0001-8018-5348, Berger, E ORCID: 0000-0002-9392-9681, Bloom, JS ORCID: 0000-0002-7777-216X, Burns, E ORCID: 0000-0002-2942-3379, Caiazzo, I ORCID: 0000-0002-4770-5388, Chandra, P ORCID: 0000-0002-0844-6563, Coughlin, MW ORCID: 0000-0002-8262-2924, El-Badry, K ORCID: 0000-0002-6871-1752, Graham, MJ ORCID: 0000-0002-3168-0139, Kasliwal, M ORCID: 0000-0002-5619-4938, Keating, GK ORCID: 0000-0002-3490-146X, Kulkarni, SR ORCID: 0000-0001-5390-8563 et al
(2025)
The Nature of Optical Afterglows without Gamma-Ray Bursts: Identification of AT2023lcr and Multiwavelength Modeling.
The Astrophysical Journal, 985 (1).
pp. 1-32.
ISSN 0004-637X
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Abstract
In the past few years, the improved sensitivity and cadence of wide-field optical surveys have enabled the discovery of several afterglows without associated detected gamma-ray bursts (GRBs). We present the identification, observations, and multiwavelength modeling of a recent such afterglow (AT2023lcr), and model three literature events (AT2020blt, AT2021any, and AT2021lfa) in a consistent fashion. For each event, we consider the following possibilities as to why a GRBwas not observed: (1) the jet was off-axis; (2) the jet had a low initial Lorentz factor; and (3) the afterglow was the result of an on-axis classical GRB (on-axis jet with physical parameters typical of the GRB population), but the emission was undetected by gamma-ray satellites. We estimate all physical parameters using afterglowpy and Markov Chain Monte Carlo methods from emcee. We find that AT2023lcr, AT2020blt, and AT2021any are consistent with on-axis classical GRBs, and AT2021lfa is consistent with both on-axis low Lorentz factor (Γ0 ≈ 5–13) and off-axis (θobs = 2θjet) high Lorentz factor (Γ0 ≈ 100) jets.
| Item Type: | Article |
|---|---|
| Uncontrolled Keywords: | 0201 Astronomical and Space Sciences; 0202 Atomic, Molecular, Nuclear, Particle and Plasma Physics; 0306 Physical Chemistry (incl. Structural); Astronomy & Astrophysics; 5101 Astronomical sciences; 5107 Particle and high energy physics; 5109 Space sciences |
| Subjects: | Q Science > QB Astronomy Q Science > QC Physics |
| Divisions: | Astrophysics Research Institute |
| Publisher: | American Astronomical Society |
| Date of acceptance: | 31 March 2025 |
| Date of first compliant Open Access: | 20 May 2025 |
| Date Deposited: | 20 May 2025 15:36 |
| Last Modified: | 03 Jul 2025 13:30 |
| DOI or ID number: | 10.3847/1538-4357/adc800 |
| URI: | https://researchonline.ljmu.ac.uk/id/eprint/26388 |
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