TY - JOUR
T1 - The Nature of Optical Afterglows without Gamma-Ray Bursts
T2 - Identification of AT2023lcr and Multiwavelength Modeling
AU - Li, Maggie L.
AU - Ho, Anna Y.Q.
AU - Ryan, Geoffrey
AU - Perley, Daniel A.
AU - Lamb, Gavin P.
AU - Nayana, A. J.
AU - Andreoni, Igor
AU - Anupama, G. C.
AU - Bellm, Eric C.
AU - Berger, Edo
AU - Bloom, Joshua S.
AU - Burns, Eric
AU - Caiazzo, Ilaria
AU - Chandra, Poonam
AU - Coughlin, Michael W.
AU - El-Badry, Kareem
AU - Graham, Matthew J.
AU - Kasliwal, Mansi
AU - Keating, Garrett K.
AU - Kulkarni, S. R.
AU - Kumar, Harsh
AU - Masci, Frank J.
AU - Perley, Richard A.
AU - Purdum, Josiah
AU - Rao, Ramprasad
AU - Rodriguez, Antonio C.
AU - Rusholme, Ben
AU - Sarin, Nikhil
AU - Sollerman, Jesper
AU - Srinivasaragavan, Gokul P.
AU - Swain, Vishwajeet
AU - Vanderbosch, Zachary
N1 - Publisher Copyright:
© 2025. The Author(s). Published by the American Astronomical Society.
PY - 2025/5/20
Y1 - 2025/5/20
N2 - 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 (Γ0 ≈ 5-13) and off-axis (θobs = 2θjet) high Lorentz factor (Γ0 ≈ 100) jets.
AB - 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 (Γ0 ≈ 5-13) and off-axis (θobs = 2θjet) high Lorentz factor (Γ0 ≈ 100) jets.
UR - https://www.scopus.com/pages/publications/105005731732
UR - https://www.scopus.com/pages/publications/105005731732#tab=citedBy
U2 - 10.3847/1538-4357/adc800
DO - 10.3847/1538-4357/adc800
M3 - Article
AN - SCOPUS:105005731732
SN - 0004-637X
VL - 985
JO - Astrophysical Journal
JF - Astrophysical Journal
IS - 1
M1 - 124
ER -