| Description: |
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. |
| Relation: |
https://researchonline.ljmu.ac.uk/id/eprint/26388/1/The%20Nature%20of%20Optical%20Afterglows%20without%20Gamma%20Ray%20Bursts%20Identification%20of%20AT2023lcr%20and%20Multiwavelength%20Modeling.pdf; Li, ML ORCID logoorcid:0009-0001-6911-9144 , Ho, AYQ ORCID logoorcid:0000-0002-9017-3567 , Ryan, G ORCID logoorcid:0000-0001-9068-7157 , Perley, DA ORCID logoorcid:0000-0001-8472-1996 , Lamb, GP ORCID logoorcid:0000-0001-5169-4143 , A.J., N ORCID logoorcid:0000-0002-8070-5400 , Andreoni, I ORCID logoorcid:0000-0002-8977-1498 , Anupama, GC ORCID logoorcid:0000-0003-3533-7183 , Bellm, EC ORCID logoorcid:0000-0001-8018-5348 , Berger, E ORCID logoorcid:0000-0002-9392-9681 , Bloom, JS ORCID logoorcid:0000-0002-7777-216X , Burns, E ORCID logoorcid:0000-0002-2942-3379 , Caiazzo, I ORCID logoorcid:0000-0002-4770-5388 , Chandra, P ORCID logoorcid:0000-0002-0844-6563 , Coughlin, MW ORCID logoorcid:0000-0002-8262-2924 , El-Badry, K ORCID logoorcid:0000-0002-6871-1752 , Graham, MJ ORCID logoorcid:0000-0002-3168-0139 , Kasliwal, M ORCID logoorcid:0000-0002-5619-4938 , Keating, GK ORCID logoorcid:0000-0002-3490-146X , Kulkarni, SR ORCID logoorcid:0000-0001-5390-8563 , Kumar, H ORCID logoorcid:0000-0003-0871-4641 , Masci, FJ ORCID logoorcid:0000-0002-8532-9395 , Perley, RA ORCID logoorcid:0000-0001-7097-8360 , Purdum, J ORCID logoorcid:0000-0003-1227-3738 , Rao, R ORCID logoorcid:0000-0002-1407-7944 , Rodriguez, AC ORCID logoorcid:0000-0003-4189-9668 , Rusholme, B ORCID logoorcid:0000-0001-7648-4142 , Sarin, N ORCID logoorcid:0000-0003-2700-1030 , Sollerman, J ORCID logoorcid:0000-0003-1546-6615 , Srinivasaragavan, GP ORCID logoorcid:0000-0002-6428-2700 , Swain, V ORCID logoorcid:0000-0002-7942-8477 and Vanderbosch, Z ORCID logoorcid:0000-0002-0853-3464 (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 |