The Nature of Optical Afterglows without Gamma-Ray Bursts: Identification of AT2023lcr and Multiwavelength Modeling

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 202...

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Main Authors: Maggie L. Li, Anna Y. Q. Ho, Geoffrey Ryan, Daniel A. Perley, Gavin P. Lamb, Nayana A.J., Igor Andreoni, G. C. Anupama, Eric C. Bellm, Edo Berger, Joshua S. Bloom, Eric Burns, Ilaria Caiazzo, Poonam Chandra, Michael W. Coughlin, Kareem El-Badry, Matthew J. Graham, Mansi Kasliwal, Garrett K. Keating, S. R. Kulkarni, Harsh Kumar, Frank J. Masci, Richard A. Perley, Josiah Purdum, Ramprasad Rao, Antonio C. Rodriguez, Ben Rusholme, Nikhil Sarin, Jesper Sollerman, Gokul P. Srinivasaragavan, Vishwajeet Swain, Zachary Vanderbosch
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Language:English
Published: IOP Publishing 2025-01-01
Series:The Astrophysical Journal
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Online Access:https://doi.org/10.3847/1538-4357/adc800
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author Maggie L. Li
Anna Y. Q. Ho
Geoffrey Ryan
Daniel A. Perley
Gavin P. Lamb
Nayana A.J.
Igor Andreoni
G. C. Anupama
Eric C. Bellm
Edo Berger
Joshua S. Bloom
Eric Burns
Ilaria Caiazzo
Poonam Chandra
Michael W. Coughlin
Kareem El-Badry
Matthew J. Graham
Mansi Kasliwal
Garrett K. Keating
S. R. Kulkarni
Harsh Kumar
Frank J. Masci
Richard A. Perley
Josiah Purdum
Ramprasad Rao
Antonio C. Rodriguez
Ben Rusholme
Nikhil Sarin
Jesper Sollerman
Gokul P. Srinivasaragavan
Vishwajeet Swain
Zachary Vanderbosch
author_facet Maggie L. Li
Anna Y. Q. Ho
Geoffrey Ryan
Daniel A. Perley
Gavin P. Lamb
Nayana A.J.
Igor Andreoni
G. C. Anupama
Eric C. Bellm
Edo Berger
Joshua S. Bloom
Eric Burns
Ilaria Caiazzo
Poonam Chandra
Michael W. Coughlin
Kareem El-Badry
Matthew J. Graham
Mansi Kasliwal
Garrett K. Keating
S. R. Kulkarni
Harsh Kumar
Frank J. Masci
Richard A. Perley
Josiah Purdum
Ramprasad Rao
Antonio C. Rodriguez
Ben Rusholme
Nikhil Sarin
Jesper Sollerman
Gokul P. Srinivasaragavan
Vishwajeet Swain
Zachary Vanderbosch
author_sort Maggie L. Li
collection DOAJ
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 (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.
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spelling doaj-art-24a6929b37554b8fb1a17ad8adcfb31d2025-08-20T01:54:57ZengIOP PublishingThe Astrophysical Journal1538-43572025-01-01985112410.3847/1538-4357/adc800The Nature of Optical Afterglows without Gamma-Ray Bursts: Identification of AT2023lcr and Multiwavelength ModelingMaggie L. Li0https://orcid.org/0009-0001-6911-9144Anna Y. Q. Ho1https://orcid.org/0000-0002-9017-3567Geoffrey Ryan2https://orcid.org/0000-0001-9068-7157Daniel A. Perley3https://orcid.org/0000-0001-8472-1996Gavin P. Lamb4https://orcid.org/0000-0001-5169-4143Nayana A.J.5https://orcid.org/0000-0002-8070-5400Igor Andreoni6https://orcid.org/0000-0002-8977-1498G. C. Anupama7https://orcid.org/0000-0003-3533-7183Eric C. Bellm8https://orcid.org/0000-0001-8018-5348Edo Berger9https://orcid.org/0000-0002-9392-9681Joshua S. Bloom10https://orcid.org/0000-0002-7777-216XEric Burns11https://orcid.org/0000-0002-2942-3379Ilaria Caiazzo12https://orcid.org/0000-0002-4770-5388Poonam Chandra13https://orcid.org/0000-0002-0844-6563Michael W. Coughlin14https://orcid.org/0000-0002-8262-2924Kareem El-Badry15https://orcid.org/0000-0002-6871-1752Matthew J. Graham16https://orcid.org/0000-0002-3168-0139Mansi Kasliwal17https://orcid.org/0000-0002-5619-4938Garrett K. Keating18https://orcid.org/0000-0002-3490-146XS. R. Kulkarni19https://orcid.org/0000-0001-5390-8563Harsh Kumar20https://orcid.org/0000-0003-0871-4641Frank J. Masci21https://orcid.org/0000-0002-8532-9395Richard A. Perley22https://orcid.org/0000-0001-7097-8360Josiah Purdum23https://orcid.org/0000-0003-1227-3738Ramprasad Rao24https://orcid.org/0000-0002-1407-7944Antonio C. Rodriguez25https://orcid.org/0000-0003-4189-9668Ben Rusholme26https://orcid.org/0000-0001-7648-4142Nikhil Sarin27https://orcid.org/0000-0003-2700-1030Jesper Sollerman28https://orcid.org/0000-0003-1546-6615Gokul P. Srinivasaragavan29https://orcid.org/0000-0002-6428-2700Vishwajeet Swain30https://orcid.org/0000-0002-7942-8477Zachary Vanderbosch31https://orcid.org/0000-0002-0853-3464Department of Astronomy, Cornell University , Ithaca, NY 14853, USA ; mll285@cornell.edu; Cahill Center for Astrophysics, California Institute of Technology , MC 249-17, 1200 E California Boulevard, Pasadena, CA 91125, USADepartment of Astronomy, Cornell University , Ithaca, NY 14853, USA ; mll285@cornell.eduPerimeter Institute for Theoretical Physics , Waterloo, Ontario N2L 2Y5, CanadaAstrophysics Research Institute, Liverpool John Moores University , IC 2, Liverpool Science Park, 146 Brownlow Hill, Liverpool L3 5RF, UKAstrophysics Research Institute, Liverpool John Moores University , IC 2, Liverpool Science Park, 146 Brownlow Hill, Liverpool L3 5RF, UKNational Centre for Radio Astrophysics, Tata Institute of Fundamental Research, Pune University Campus , Ganeshkhind Pune 411007, IndiaJoint Space-Science Institute, University of Maryland , College Park, MD 20742, USA; Department of Astronomy, University of Maryland , College Park, MD 20742, USA; Astrophysics Science Division , NASA Goddard Space Flight Center, 8800 Greenbelt Road, Greenbelt, MD 20771, USA; University of North Carolina at Chapel Hill , 120 E. Cameron Avenue, Chapel Hill, NC 27514, USAIndian Institute of Astrophysics , II Block Koramangala, Bengaluru 560034, IndiaDIRAC Institute, Department of Astronomy, University of Washington , 3910 15th Avenue NE, Seattle, WA 98195, USACenter for Astrophysics ∣ Harvard & Smithsonian , 60 Garden Street, Cambridge, MA 02138-1516, USADepartment of Astronomy, University of California , Berkeley, CA 94720, USA; Physics Division, Lawrence Berkeley National Laboratory , 1 Cyclotron Road, MS 50B-4206, Berkeley, CA 94720, USADepartment of Physics & Astronomy, Louisiana State University , Baton Rouge, LA 70803, USACahill Center for Astrophysics, California Institute of Technology , MC 249-17, 1200 E California Boulevard, Pasadena, CA 91125, USANational Radio Astronomy Observatory , 520 Edgemont Road, Charlottesville, VA 22903, USASchool of Physics and Astronomy, University of Minnesota , Minneapolis, MN 55455, USACahill Center for Astrophysics, California Institute of Technology , MC 249-17, 1200 E California Boulevard, Pasadena, CA 91125, USACahill Center for Astrophysics, California Institute of Technology , MC 249-17, 1200 E California Boulevard, Pasadena, CA 91125, USACahill Center for Astrophysics, California Institute of Technology , MC 249-17, 1200 E California Boulevard, Pasadena, CA 91125, USACenter for Astrophysics ∣ Harvard & Smithsonian , 60 Garden Street, Cambridge, MA 02138-1516, USACahill Center for Astrophysics, California Institute of Technology , MC 249-17, 1200 E California Boulevard, Pasadena, CA 91125, USACenter for Astrophysics ∣ Harvard & Smithsonian , 60 Garden Street, Cambridge, MA 02138-1516, USA; Physics Department, Indian Institute of Technology Bombay , Powai, 400 076, India; The NSF AI Institute for Artificial Intelligence and Fundamental Interactions , USAIPAC, California Institute of Technology , 1200 E. California Boulevard, Pasadena, CA 91125, USANational Radio Astronomy Observatory , PO Box 0, Socorro, NM 87801, USACaltech Optical Observatories, California Institute of Technology , Pasadena, CA 91125, USACenter for Astrophysics ∣ Harvard & Smithsonian , 60 Garden Street, Cambridge, MA 02138-1516, USACahill Center for Astrophysics, California Institute of Technology , MC 249-17, 1200 E California Boulevard, Pasadena, CA 91125, USAIPAC, California Institute of Technology , 1200 E. California Boulevard, Pasadena, CA 91125, USANordita, Stockholm University and KTH Royal Institute of Technology , Hannes Alfvens vag 12, SE-106 91 Stockholm, Sweden; Oskar Klein Centre for Cosmoparticle Physics, Department of Physics, Stockholm University , AlbaNova, Stockholm SE-106 91, SwedenOskar Klein Centre, Department of Astronomy, Stockholm University , AlbaNova, SE-10691 Stockholm, SwedenJoint Space-Science Institute, University of Maryland , College Park, MD 20742, USA; Department of Astronomy, University of Maryland , College Park, MD 20742, USA; Astrophysics Science Division , NASA Goddard Space Flight Center, 8800 Greenbelt Road, Greenbelt, MD 20771, USADepartment of Physics, Indian Institute of Technology Bombay , Powai, 400 076, IndiaCahill Center for Astrophysics, California Institute of Technology , MC 249-17, 1200 E California Boulevard, Pasadena, CA 91125, USAIn 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.https://doi.org/10.3847/1538-4357/adc800Gamma-ray burstsTransient sourcesSurveysSky surveysRadio transient sourcesX-ray transient sources
spellingShingle Maggie L. Li
Anna Y. Q. Ho
Geoffrey Ryan
Daniel A. Perley
Gavin P. Lamb
Nayana A.J.
Igor Andreoni
G. C. Anupama
Eric C. Bellm
Edo Berger
Joshua S. Bloom
Eric Burns
Ilaria Caiazzo
Poonam Chandra
Michael W. Coughlin
Kareem El-Badry
Matthew J. Graham
Mansi Kasliwal
Garrett K. Keating
S. R. Kulkarni
Harsh Kumar
Frank J. Masci
Richard A. Perley
Josiah Purdum
Ramprasad Rao
Antonio C. Rodriguez
Ben Rusholme
Nikhil Sarin
Jesper Sollerman
Gokul P. Srinivasaragavan
Vishwajeet Swain
Zachary Vanderbosch
The Nature of Optical Afterglows without Gamma-Ray Bursts: Identification of AT2023lcr and Multiwavelength Modeling
The Astrophysical Journal
Gamma-ray bursts
Transient sources
Surveys
Sky surveys
Radio transient sources
X-ray transient sources
title The Nature of Optical Afterglows without Gamma-Ray Bursts: Identification of AT2023lcr and Multiwavelength Modeling
title_full The Nature of Optical Afterglows without Gamma-Ray Bursts: Identification of AT2023lcr and Multiwavelength Modeling
title_fullStr The Nature of Optical Afterglows without Gamma-Ray Bursts: Identification of AT2023lcr and Multiwavelength Modeling
title_full_unstemmed The Nature of Optical Afterglows without Gamma-Ray Bursts: Identification of AT2023lcr and Multiwavelength Modeling
title_short The Nature of Optical Afterglows without Gamma-Ray Bursts: Identification of AT2023lcr and Multiwavelength Modeling
title_sort nature of optical afterglows without gamma ray bursts identification of at2023lcr and multiwavelength modeling
topic Gamma-ray bursts
Transient sources
Surveys
Sky surveys
Radio transient sources
X-ray transient sources
url https://doi.org/10.3847/1538-4357/adc800
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