Discovery and analysis of afterglows from poorly localized GRBs with the Gravitational-wave Optical Transient Observer (GOTO) All-sky Survey

Amit Kumar; B P Gompertz; B Schneider; S Belkin; M E Wortley; A Saccardi; D O’Neill; K Ackley; B Rayson; A de Ugarte Postigo; A Gulati; D Steeghs; D B Malesani; J R Maund; M J Dyer; S Giarratana; M Serino; Y Julakanti; B Kumar; D Xu; R A J Eyles-Ferris; Z -P Zhu; B Warwick; Y -D Hu; I Allen; G Ramsay; R L C Starling; J Lyman; K Ulaczyk; B Godson; D K Galloway; V S Dhillon; P O’Brien; K Noysena; R Kotak; R P Breton; L K Nuttall; D Pollacco; J Casares; T L Killestein; M R Kennedy; N Habeeb; S Moran; K Wiersema; I Worssam; D L Coppejans; C A Phillips; A Martin-Carrillo; N S Pankov; J F Agüí Fernández; M A Aloy; J An; G E Anderson; A Bochenek; A J Castro-Tirado; X Chen; L Cotter; R Dastidar; M De Pasquale; V D’Elia; Y Fang; S Y Fu; J P U Fynbo; D H Hartmann; L B He; L Izzo; S Q Jiang; Y Kawakubo; E V Klunko; A J Levan; X-W Liu; X Liu; G Lombardi; E Maiorano; J T Palmerio; D A Perley; D L A Pieterse; A S Pozanenko; G Pugliese; A Rossi; B Sbarufatti; S Bijavara Seshashayana; N R Tanvir; C C Thöne; A J van der Horst; S D Vergani; A A Volnova; R A M J Wijers; J L Wise

doi:10.1093/mnras/staf1689

Discovery and analysis of afterglows from poorly localized GRBs with the Gravitational-wave Optical Transient Observer (GOTO) All-sky Survey

Amit Kumar
, B P Gompertz
, B Schneider
, S Belkin
, M E Wortley
, A Saccardi
, D O’Neill
, K Ackley
, B Rayson
, A de Ugarte Postigo
, A Gulati
, D Steeghs
, D B Malesani
, J R Maund
, M J Dyer
, S Giarratana
, M Serino
, Y Julakanti
, B Kumar
, D Xu

R A J Eyles-Ferris, Z -P Zhu, B Warwick, Y -D Hu, I Allen, G Ramsay, R L C Starling, J Lyman, K Ulaczyk, B Godson, D K Galloway, V S Dhillon, P O’Brien, K Noysena, R Kotak, R P Breton, L K Nuttall, D Pollacco, J Casares, T L Killestein, M R Kennedy, N Habeeb, S Moran, K Wiersema, I Worssam, D L Coppejans, C A Phillips, A Martin-Carrillo, N S Pankov, J F Agüí Fernández, M A Aloy, J An, G E Anderson, A Bochenek, A J Castro-Tirado, X Chen, L Cotter, R Dastidar, M De Pasquale, V D’Elia, Y Fang, S Y Fu, J P U Fynbo, D H Hartmann, L B He, L Izzo, S Q Jiang, Y Kawakubo, E V Klunko, A J Levan, X-W Liu, X Liu, G Lombardi, E Maiorano, J T Palmerio, D A Perley, D L A Pieterse, A S Pozanenko, G Pugliese, A Rossi, B Sbarufatti, S Bijavara Seshashayana, N R Tanvir, C C Thöne, A J van der Horst, S D Vergani, A A Volnova, R A M J Wijers, J L Wise

Research output: Contribution to journal › Article › peer-review

2 Citations (Scopus)

7 Downloads (Pure)

Abstract

Gamma-ray bursts (GRBs), particularly those detected by wide-field instruments such as the Fermi/GBM, pose challenges for optical follow-up because of their large initial localization regions, leaving many GRBs without identified afterglows. The Gravitational-wave Optical Transient Observer (GOTO), with its wide field of view, dual-site coverage, and robotic rapid-response capability, bridges this gap by rapidly identifying and localizing afterglows from alerts issued by space-based facilities including Fermi, SVOM, Swift, and the EP, providing early optical positions for coordinated multiwavelength follow-up. In this paper, we present optical afterglow localization and multiband follow-up of five Fermi/GBM (240619A, 240910A, 240916A, 241002B, and 241228B) and two MAXI/GSC (240122A and 240225B) triggered long GRBs discovered by GOTO in 2024. Spectroscopy for six GRBs (no spectroscopy for GRB 241002B) with VLT/X-shooter and GTC/OSIRIS yields precise redshifts spanning –3.16 and absorption-line diagnostics of hosts and intervening systems. Radio detections for four events (240122A, 240619A, 240910A, and 240916A) confirm the presence of long-lived synchrotron emission. Prompt-emission analysis with Fermi and MAXI data reveals a spectrally hard population, with two bursts lying above the Amati relation. Although their optical afterglows resemble those of typical long GRBs, the prompt spectra are consistently harder than the long-GRB average. Broad-band afterglow modelling of six GOTO-discovered GRBs yields jet half-opening angles of a few degrees and beaming-corrected kinetic energies – erg, consistent with the canonical long-GRB population. These findings suggest that optical discovery of poorly localized GRBs is likely subject to observational biases favouring luminous events with high spectral peak energy (), while also providing insight into jet microphysics and central engine diversity.

Original language	English
Pages (from-to)	1541-1587
Number of pages	47
Journal	Monthly Notices of the Royal Astronomical Society
Volume	544
Issue number	2
Early online date	3 Oct 2025
DOIs	https://doi.org/10.1093/mnras/staf1689
Publication status	Published - 31 Dec 2025

Keywords

gamma-ray bursts
techniques: spectroscopic
techniques: photometric
gamma-ray burst: individual: GRB 240122A, GRB 240225B, GRB 240619A, GRB 240910A, GRB 240916A, GRB 241002B, GRB 241228B

Access to Document

10.1093/mnras/staf1689Licence: CC BY

Final_versionFinal published version, 16.3 MBLicence: CC BY

Cite this

Kumar, A., Gompertz, B. P., Schneider, B., Belkin, S., Wortley, M. E., Saccardi, A., O’Neill, D., Ackley, K., Rayson, B., Postigo, A. D. U., Gulati, A., Steeghs, D., Malesani, D. B., Maund, J. R., Dyer, M. J., Giarratana, S., Serino, M., Julakanti, Y., Kumar, B., ... Wise, J. L. (2025). Discovery and analysis of afterglows from poorly localized GRBs with the Gravitational-wave Optical Transient Observer (GOTO) All-sky Survey. Monthly Notices of the Royal Astronomical Society, 544(2), 1541-1587. https://doi.org/10.1093/mnras/staf1689

@article{434560b349ad464cb1b46e6e356abf67,

title = "Discovery and analysis of afterglows from poorly localized GRBs with the Gravitational-wave Optical Transient Observer (GOTO) All-sky Survey",

abstract = "Gamma-ray bursts (GRBs), particularly those detected by wide-field instruments such as the Fermi/GBM, pose challenges for optical follow-up because of their large initial localization regions, leaving many GRBs without identified afterglows. The Gravitational-wave Optical Transient Observer (GOTO), with its wide field of view, dual-site coverage, and robotic rapid-response capability, bridges this gap by rapidly identifying and localizing afterglows from alerts issued by space-based facilities including Fermi, SVOM, Swift, and the EP, providing early optical positions for coordinated multiwavelength follow-up. In this paper, we present optical afterglow localization and multiband follow-up of five Fermi/GBM (240619A, 240910A, 240916A, 241002B, and 241228B) and two MAXI/GSC (240122A and 240225B) triggered long GRBs discovered by GOTO in 2024. Spectroscopy for six GRBs (no spectroscopy for GRB 241002B) with VLT/X-shooter and GTC/OSIRIS yields precise redshifts spanning {\textendash}3.16 and absorption-line diagnostics of hosts and intervening systems. Radio detections for four events (240122A, 240619A, 240910A, and 240916A) confirm the presence of long-lived synchrotron emission. Prompt-emission analysis with Fermi and MAXI data reveals a spectrally hard population, with two bursts lying above the Amati relation. Although their optical afterglows resemble those of typical long GRBs, the prompt spectra are consistently harder than the long-GRB average. Broad-band afterglow modelling of six GOTO-discovered GRBs yields jet half-opening angles of a few degrees and beaming-corrected kinetic energies {\textendash} erg, consistent with the canonical long-GRB population. These findings suggest that optical discovery of poorly localized GRBs is likely subject to observational biases favouring luminous events with high spectral peak energy (), while also providing insight into jet microphysics and central engine diversity.",

keywords = "gamma-ray bursts, techniques: spectroscopic, techniques: photometric, gamma-ray burst: individual: GRB 240122A, GRB 240225B, GRB 240619A, GRB 240910A, GRB 240916A, GRB 241002B, GRB 241228B",

author = "Amit Kumar and Gompertz, \{B P\} and B Schneider and S Belkin and Wortley, \{M E\} and A Saccardi and D O{\textquoteright}Neill and K Ackley and B Rayson and Postigo, \{A de Ugarte\} and A Gulati and D Steeghs and Malesani, \{D B\} and Maund, \{J R\} and Dyer, \{M J\} and S Giarratana and M Serino and Y Julakanti and B Kumar and D Xu and Eyles-Ferris, \{R A J\} and Zhu, \{Z -P\} and B Warwick and Hu, \{Y -D\} and I Allen and G Ramsay and Starling, \{R L C\} and J Lyman and K Ulaczyk and B Godson and Galloway, \{D K\} and Dhillon, \{V S\} and P O{\textquoteright}Brien and K Noysena and R Kotak and Breton, \{R P\} and Nuttall, \{L K\} and D Pollacco and J Casares and Killestein, \{T L\} and Kennedy, \{M R\} and N Habeeb and S Moran and K Wiersema and I Worssam and Coppejans, \{D L\} and Phillips, \{C A\} and A Martin-Carrillo and Pankov, \{N S\} and Fern{\'a}ndez, \{J F Ag{\"u}{\'i}\} and Aloy, \{M A\} and J An and Anderson, \{G E\} and A Bochenek and Castro-Tirado, \{A J\} and X Chen and L Cotter and R Dastidar and M De Pasquale and V D{\textquoteright}Elia and Y Fang and Fu, \{S Y\} and Fynbo, \{J P U\} and Hartmann, \{D H\} and He, \{L B\} and L Izzo and Jiang, \{S Q\} and Y Kawakubo and Klunko, \{E V\} and Levan, \{A J\} and X-W Liu and X Liu and G Lombardi and E Maiorano and Palmerio, \{J T\} and Perley, \{D A\} and Pieterse, \{D L A\} and Pozanenko, \{A S\} and G Pugliese and A Rossi and B Sbarufatti and Seshashayana, \{S Bijavara\} and Tanvir, \{N R\} and Th{\"o}ne, \{C C\} and \{van der Horst\}, \{A J\} and Vergani, \{S D\} and Volnova, \{A A\} and Wijers, \{R A M J\} and Wise, \{J L\}",

note = "{\textcopyright} The Author(s) 2025. Published by Oxford University Press on behalf of Royal Astronomical Society. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0/)",

year = "2025",

month = dec,

day = "31",

doi = "10.1093/mnras/staf1689",

language = "English",

volume = "544",

pages = "1541--1587",

journal = "Monthly Notices of the Royal Astronomical Society",

issn = "0035-8711",

publisher = "Oxford University Press (OUP)",

number = "2",

}

Kumar, A, Gompertz, BP, Schneider, B, Belkin, S, Wortley, ME, Saccardi, A, O’Neill, D, Ackley, K, Rayson, B, Postigo, ADU, Gulati, A, Steeghs, D, Malesani, DB, Maund, JR, Dyer, MJ, Giarratana, S, Serino, M, Julakanti, Y, Kumar, B, Xu, D, Eyles-Ferris, RAJ, Zhu, Z-P, Warwick, B, Hu, Y-D, Allen, I, Ramsay, G, Starling, RLC, Lyman, J, Ulaczyk, K, Godson, B, Galloway, DK, Dhillon, VS, O’Brien, P, Noysena, K, Kotak, R, Breton, RP, Nuttall, LK, Pollacco, D, Casares, J, Killestein, TL, Kennedy, MR, Habeeb, N, Moran, S, Wiersema, K, Worssam, I, Coppejans, DL, Phillips, CA, Martin-Carrillo, A, Pankov, NS, Fernández, JFA, Aloy, MA, An, J, Anderson, GE, Bochenek, A, Castro-Tirado, AJ, Chen, X, Cotter, L, Dastidar, R, De Pasquale, M, D’Elia, V, Fang, Y, Fu, SY, Fynbo, JPU, Hartmann, DH, He, LB, Izzo, L, Jiang, SQ, Kawakubo, Y, Klunko, EV, Levan, AJ, Liu, X-W, Liu, X, Lombardi, G, Maiorano, E, Palmerio, JT, Perley, DA, Pieterse, DLA, Pozanenko, AS, Pugliese, G, Rossi, A, Sbarufatti, B, Seshashayana, SB, Tanvir, NR, Thöne, CC, van der Horst, AJ, Vergani, SD, Volnova, AA, Wijers, RAMJ & Wise, JL 2025, 'Discovery and analysis of afterglows from poorly localized GRBs with the Gravitational-wave Optical Transient Observer (GOTO) All-sky Survey', Monthly Notices of the Royal Astronomical Society, vol. 544, no. 2, pp. 1541-1587. https://doi.org/10.1093/mnras/staf1689

TY - JOUR

T1 - Discovery and analysis of afterglows from poorly localized GRBs with the Gravitational-wave Optical Transient Observer (GOTO) All-sky Survey

AU - Kumar, Amit

AU - Gompertz, B P

AU - Schneider, B

AU - Belkin, S

AU - Wortley, M E

AU - Saccardi, A

AU - O’Neill, D

AU - Ackley, K

AU - Rayson, B

AU - Postigo, A de Ugarte

AU - Gulati, A

AU - Steeghs, D

AU - Malesani, D B

AU - Maund, J R

AU - Dyer, M J

AU - Giarratana, S

AU - Serino, M

AU - Julakanti, Y

AU - Kumar, B

AU - Xu, D

AU - Eyles-Ferris, R A J

AU - Zhu, Z -P

AU - Warwick, B

AU - Hu, Y -D

AU - Allen, I

AU - Ramsay, G

AU - Starling, R L C

AU - Lyman, J

AU - Ulaczyk, K

AU - Godson, B

AU - Galloway, D K

AU - Dhillon, V S

AU - O’Brien, P

AU - Noysena, K

AU - Kotak, R

AU - Breton, R P

AU - Nuttall, L K

AU - Pollacco, D

AU - Casares, J

AU - Killestein, T L

AU - Kennedy, M R

AU - Habeeb, N

AU - Moran, S

AU - Wiersema, K

AU - Worssam, I

AU - Coppejans, D L

AU - Phillips, C A

AU - Martin-Carrillo, A

AU - Pankov, N S

AU - Fernández, J F Agüí

AU - Aloy, M A

AU - An, J

AU - Anderson, G E

AU - Bochenek, A

AU - Castro-Tirado, A J

AU - Chen, X

AU - Cotter, L

AU - Dastidar, R

AU - De Pasquale, M

AU - D’Elia, V

AU - Fang, Y

AU - Fu, S Y

AU - Fynbo, J P U

AU - Hartmann, D H

AU - He, L B

AU - Izzo, L

AU - Jiang, S Q

AU - Kawakubo, Y

AU - Klunko, E V

AU - Levan, A J

AU - Liu, X-W

AU - Liu, X

AU - Lombardi, G

AU - Maiorano, E

AU - Palmerio, J T

AU - Perley, D A

AU - Pieterse, D L A

AU - Pozanenko, A S

AU - Pugliese, G

AU - Rossi, A

AU - Sbarufatti, B

AU - Seshashayana, S Bijavara

AU - Tanvir, N R

AU - Thöne, C C

AU - van der Horst, A J

AU - Vergani, S D

AU - Volnova, A A

AU - Wijers, R A M J

AU - Wise, J L

N1 - © The Author(s) 2025. Published by Oxford University Press on behalf of Royal Astronomical Society. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0/)

PY - 2025/12/31

Y1 - 2025/12/31

N2 - Gamma-ray bursts (GRBs), particularly those detected by wide-field instruments such as the Fermi/GBM, pose challenges for optical follow-up because of their large initial localization regions, leaving many GRBs without identified afterglows. The Gravitational-wave Optical Transient Observer (GOTO), with its wide field of view, dual-site coverage, and robotic rapid-response capability, bridges this gap by rapidly identifying and localizing afterglows from alerts issued by space-based facilities including Fermi, SVOM, Swift, and the EP, providing early optical positions for coordinated multiwavelength follow-up. In this paper, we present optical afterglow localization and multiband follow-up of five Fermi/GBM (240619A, 240910A, 240916A, 241002B, and 241228B) and two MAXI/GSC (240122A and 240225B) triggered long GRBs discovered by GOTO in 2024. Spectroscopy for six GRBs (no spectroscopy for GRB 241002B) with VLT/X-shooter and GTC/OSIRIS yields precise redshifts spanning –3.16 and absorption-line diagnostics of hosts and intervening systems. Radio detections for four events (240122A, 240619A, 240910A, and 240916A) confirm the presence of long-lived synchrotron emission. Prompt-emission analysis with Fermi and MAXI data reveals a spectrally hard population, with two bursts lying above the Amati relation. Although their optical afterglows resemble those of typical long GRBs, the prompt spectra are consistently harder than the long-GRB average. Broad-band afterglow modelling of six GOTO-discovered GRBs yields jet half-opening angles of a few degrees and beaming-corrected kinetic energies – erg, consistent with the canonical long-GRB population. These findings suggest that optical discovery of poorly localized GRBs is likely subject to observational biases favouring luminous events with high spectral peak energy (), while also providing insight into jet microphysics and central engine diversity.

AB - Gamma-ray bursts (GRBs), particularly those detected by wide-field instruments such as the Fermi/GBM, pose challenges for optical follow-up because of their large initial localization regions, leaving many GRBs without identified afterglows. The Gravitational-wave Optical Transient Observer (GOTO), with its wide field of view, dual-site coverage, and robotic rapid-response capability, bridges this gap by rapidly identifying and localizing afterglows from alerts issued by space-based facilities including Fermi, SVOM, Swift, and the EP, providing early optical positions for coordinated multiwavelength follow-up. In this paper, we present optical afterglow localization and multiband follow-up of five Fermi/GBM (240619A, 240910A, 240916A, 241002B, and 241228B) and two MAXI/GSC (240122A and 240225B) triggered long GRBs discovered by GOTO in 2024. Spectroscopy for six GRBs (no spectroscopy for GRB 241002B) with VLT/X-shooter and GTC/OSIRIS yields precise redshifts spanning –3.16 and absorption-line diagnostics of hosts and intervening systems. Radio detections for four events (240122A, 240619A, 240910A, and 240916A) confirm the presence of long-lived synchrotron emission. Prompt-emission analysis with Fermi and MAXI data reveals a spectrally hard population, with two bursts lying above the Amati relation. Although their optical afterglows resemble those of typical long GRBs, the prompt spectra are consistently harder than the long-GRB average. Broad-band afterglow modelling of six GOTO-discovered GRBs yields jet half-opening angles of a few degrees and beaming-corrected kinetic energies – erg, consistent with the canonical long-GRB population. These findings suggest that optical discovery of poorly localized GRBs is likely subject to observational biases favouring luminous events with high spectral peak energy (), while also providing insight into jet microphysics and central engine diversity.

KW - gamma-ray bursts

KW - techniques: spectroscopic

KW - techniques: photometric

KW - gamma-ray burst: individual: GRB 240122A, GRB 240225B, GRB 240619A, GRB 240910A, GRB 240916A, GRB 241002B, GRB 241228B

U2 - 10.1093/mnras/staf1689

DO - 10.1093/mnras/staf1689

M3 - Article

SN - 0035-8711

VL - 544

SP - 1541

EP - 1587

JO - Monthly Notices of the Royal Astronomical Society

JF - Monthly Notices of the Royal Astronomical Society

IS - 2

ER -

Discovery and analysis of afterglows from poorly localized GRBs with the Gravitational-wave Optical Transient Observer (GOTO) All-sky Survey

Abstract

Keywords

Access to Document

Fingerprint

Cite this