The Nature of Optical Afterglows without Gamma-Ray Bursts: Identification of AT2023lcr and Multiwavelength Modeling
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 (AT 2023lcr), and model three literature events (AT 2020blt, AT 2021any, and AT 2021lfa) in a consistent fashion. For each event, we consider the following possibilities as to why a GRB was 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 AT 2023lcr, AT 2020blt, and AT 2021any are consistent with on-axis classical GRBs, and AT 2021lfa is consistent with both on-axis low Lorentz factor (Γ 0 ≈ 5–13) and off-axis ( θ obs = 2 θ jet ) high Lorentz factor (Γ 0 ≈ 100) jets.
Authors
- Gokul P. Srinivasaragavan (ORCID: https://orcid.org/0000-0002-6428-2700)
- Garrett K. Keating (ORCID: https://orcid.org/0000-0002-3490-146X)
- Maggie L. Li
- J. Sollerman (ORCID: https://orcid.org/0000-0003-1546-6615)
- Vishwajeet Swain (ORCID: https://orcid.org/0000-0002-7942-8477)
- Antonio C. Rodriguez (ORCID: https://orcid.org/0000-0003-4189-9668)
- M. J. Graham (ORCID: https://orcid.org/0000-0002-3168-0139)
- Ilaria Caiazzo (ORCID: https://orcid.org/0000-0002-4770-5388)
- Kareem J. El-Badry (ORCID: https://orcid.org/0000-0002-6871-1752)
- Ramprasad Rao (ORCID: https://orcid.org/0000-0002-1407-7944)
- Frank J. Masci (ORCID: https://orcid.org/0000-0002-8532-9395)
- P. Chandra (ORCID: https://orcid.org/0000-0002-0844-6563)
- Harsh Kumar (ORCID: https://orcid.org/0000-0003-0871-4641)
- Josiah Purdum (ORCID: https://orcid.org/0000-0003-1227-3738)
- G. C. Anupama (ORCID: https://orcid.org/0000-0003-3533-7183)
- S. R. Kulkarni (ORCID: https://orcid.org/0000-0001-5390-8563)
- Gavin P. Lamb (ORCID: https://orcid.org/0000-0001-5169-4143)
- E. Berger (ORCID: https://orcid.org/0000-0002-9392-9681)
- D. A. Perley (ORCID: https://orcid.org/0000-0001-8472-1996)
- J. S. Bloom (ORCID: https://orcid.org/0000-0002-7777-216X)
- M. W. Coughlin (ORCID: https://orcid.org/0000-0002-8262-2924)
- Igor Andreoni (ORCID: https://orcid.org/0000-0002-8977-1498)
- Anna Y. Q. Ho (ORCID: https://orcid.org/0000-0002-9017-3567)
- Eric C. Bellm (ORCID: https://orcid.org/0000-0001-8018-5348)
- Zachary P. Vanderbosch (ORCID: https://orcid.org/0000-0002-0853-3464)
- Geoffrey Ryan (ORCID: https://orcid.org/0000-0001-9068-7157)
- Eric Burns (ORCID: https://orcid.org/0000-0002-2942-3379)
- R. A. Perley (ORCID: https://orcid.org/0000-0001-7097-8360)
- B. Rusholme (ORCID: https://orcid.org/0000-0001-7648-4142)
- Nikhil Sarin (ORCID: https://orcid.org/0000-0003-2700-1030)
- M. M. Kasliwal (ORCID: https://orcid.org/0000-0002-5619-4938)
- Nayana A.J.
Publication Details
- Journal
- The Astrophysical Journal
- Published
- 2025-05-19
- DOI
- https://doi.org/10.3847/1538-4357/adc800
- Citations
- 3
- Primary Topic
- Gamma-ray bursts and supernovae
- Type
- article
- Field-Weighted Citation Impact
- 3.46