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author Pieterse, Daniëlle L. A.
Levan, Andrew J.
Ravasio, Maria E.
Rastinejad, Jillian C.
van Hoof, Agnes P. C.
Malesani, Daniele B.
Sarin, Nikhil
Lamb, Gavin P.
Martin-Carrillo, Antonio
Nugent, Anya E.
Tanvir, Nial R.
Jonker, Peter G.
Kann, David Alexander
Fernández, José Feliciano Agüí
Berger, Edo
Corcoran, Gregory
Cusano, Felice
D'Avanzo, Paolo
D'Elia, Valerio
Postigo, Antonio de Ugarte
Dimple
Fong, Wen-fai
Fynbo, Johan P. U.
Izzo, Luca
Maiorano, Elisabetta
Melandri, Andrea
Palazzi, Eliana
Quirola-Vásquez, Jonathan
Rossi, Andrea
Escorial, Alicia Rouco
author_facet Pieterse, Daniëlle L. A.
Levan, Andrew J.
Ravasio, Maria E.
Rastinejad, Jillian C.
van Hoof, Agnes P. C.
Malesani, Daniele B.
Sarin, Nikhil
Lamb, Gavin P.
Martin-Carrillo, Antonio
Nugent, Anya E.
Tanvir, Nial R.
Jonker, Peter G.
Kann, David Alexander
Fernández, José Feliciano Agüí
Berger, Edo
Corcoran, Gregory
Cusano, Felice
D'Avanzo, Paolo
D'Elia, Valerio
Postigo, Antonio de Ugarte
Dimple
Fong, Wen-fai
Fynbo, Johan P. U.
Izzo, Luca
Maiorano, Elisabetta
Melandri, Andrea
Palazzi, Eliana
Quirola-Vásquez, Jonathan
Rossi, Andrea
Escorial, Alicia Rouco
contents We present detailed, multi-wavelength analysis of GRB 210704A: a Fermi Gamma-ray Burst Monitor discovered and Fermi Large Area Telescope (LAT) detected gamma-ray burst (GRB). The burst is dominated by a short ($\approx 2$ s) pulse followed by weaker, softer emission. We line stack our afterglow spectrum and determine the most likely redshift to be $z = 2.34$. This is corroborated by the photometric redshift of the extended source underlying the GRB. The spectral energy distribution fit parameters, late-time imaging, as well as the GRB's energetics, spectral lag, and location point to a collapsar nature. Follow-up observations reveal excess optical/infrared emission with respect to a standard afterglow, peaking around $T_0 + 7$ d ($2$ d in the rest frame). The excess is extremely luminous ($M_{r} = -22.0$ mag) and rapidly evolving. Strikingly, it resembles the emission seen in recently discovered Einstein Probe fast X-ray transients EP241021a and EP240414a, as well as the population of luminous fast blue optical transients (LFBOTs). This provides a link between these sources and GRBs. Fermi/LAT observations imply a high Lorentz factor, making this a case where LFBOT-like emission is also associated with a powerful successfully launched jet. We model the excess as likely coming from an energetic refreshed shock.
format Preprint
id arxiv_https___arxiv_org_abs_2604_14343
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle GRB 210704A: A Luminous Fast Blue Transient in a GRB Afterglow at $z = 2.34$
Pieterse, Daniëlle L. A.
Levan, Andrew J.
Ravasio, Maria E.
Rastinejad, Jillian C.
van Hoof, Agnes P. C.
Malesani, Daniele B.
Sarin, Nikhil
Lamb, Gavin P.
Martin-Carrillo, Antonio
Nugent, Anya E.
Tanvir, Nial R.
Jonker, Peter G.
Kann, David Alexander
Fernández, José Feliciano Agüí
Berger, Edo
Corcoran, Gregory
Cusano, Felice
D'Avanzo, Paolo
D'Elia, Valerio
Postigo, Antonio de Ugarte
Dimple
Fong, Wen-fai
Fynbo, Johan P. U.
Izzo, Luca
Maiorano, Elisabetta
Melandri, Andrea
Palazzi, Eliana
Quirola-Vásquez, Jonathan
Rossi, Andrea
Escorial, Alicia Rouco
High Energy Astrophysical Phenomena
We present detailed, multi-wavelength analysis of GRB 210704A: a Fermi Gamma-ray Burst Monitor discovered and Fermi Large Area Telescope (LAT) detected gamma-ray burst (GRB). The burst is dominated by a short ($\approx 2$ s) pulse followed by weaker, softer emission. We line stack our afterglow spectrum and determine the most likely redshift to be $z = 2.34$. This is corroborated by the photometric redshift of the extended source underlying the GRB. The spectral energy distribution fit parameters, late-time imaging, as well as the GRB's energetics, spectral lag, and location point to a collapsar nature. Follow-up observations reveal excess optical/infrared emission with respect to a standard afterglow, peaking around $T_0 + 7$ d ($2$ d in the rest frame). The excess is extremely luminous ($M_{r} = -22.0$ mag) and rapidly evolving. Strikingly, it resembles the emission seen in recently discovered Einstein Probe fast X-ray transients EP241021a and EP240414a, as well as the population of luminous fast blue optical transients (LFBOTs). This provides a link between these sources and GRBs. Fermi/LAT observations imply a high Lorentz factor, making this a case where LFBOT-like emission is also associated with a powerful successfully launched jet. We model the excess as likely coming from an energetic refreshed shock.
title GRB 210704A: A Luminous Fast Blue Transient in a GRB Afterglow at $z = 2.34$
topic High Energy Astrophysical Phenomena
url https://arxiv.org/abs/2604.14343