An Extremely Bright Slow-rising Afterglow from an Off-axis Jet in GRB 260310A

@article{yang2026extremely,
  title = {{An Extremely Bright Slow-rising Afterglow from an Off-axis Jet in GRB 260310A}},
  author = {Yu-Han Yang and Roberto Ricci and Eleonora Troja and Muskan Yadav and Yi-Han Iris Yin and Rubén Sánchez-Ramírez and Brendan O’Connor and Niccolò Passaleva and Alberto J. Castro-Tirado and Hendrik van Eerten and Simone Dichiara and Vincenzo Galluzzi and Narjes Shahamat Dehsorkh and Iván Agudo and Jesús Aceituno and Malte Busmann and Maria D. Caballero-García and Emilio Fernández-García and Daniel Gruen and Maria Gritsevich and Sergiy Guziy and David Hiriart and You-Dong Hu and Martin Jelínek and Alexander Kutyrev and Alzbeta Malenakova and Filip Novotny and Ignacio Pérez-García and Shashi B. Pandey and Jorma Ryske and Alfredo Sota and Jan Strobl and Hira Waseem and Siyu Wu},
  journal = {The Astrophysical Journal Letters},
  year = {2026},
  month = oct,
  doi = {10.3847/2041-8213/aea990},
  url = {https://iopscience.iop.org/article/10.3847/2041-8213/aea990},
  note = {CC BY 4.0},
}

TY  - JOUR
TI  - An Extremely Bright Slow-rising Afterglow from an Off-axis Jet in GRB 260310A
AU  - Yu-Han Yang
AU  - Roberto Ricci
AU  - Eleonora Troja
AU  - Muskan Yadav
AU  - Yi-Han Iris Yin
AU  - Rubén Sánchez-Ramírez
AU  - Brendan O’Connor
AU  - Niccolò Passaleva
AU  - Alberto J. Castro-Tirado
AU  - Hendrik van Eerten
AU  - Simone Dichiara
AU  - Vincenzo Galluzzi
AU  - Narjes Shahamat Dehsorkh
AU  - Iván Agudo
AU  - Jesús Aceituno
AU  - Malte Busmann
AU  - Maria D. Caballero-García
AU  - Emilio Fernández-García
AU  - Daniel Gruen
AU  - Maria Gritsevich
AU  - Sergiy Guziy
AU  - David Hiriart
AU  - You-Dong Hu
AU  - Martin Jelínek
AU  - Alexander Kutyrev
AU  - Alzbeta Malenakova
AU  - Filip Novotny
AU  - Ignacio Pérez-García
AU  - Shashi B. Pandey
AU  - Jorma Ryske
AU  - Alfredo Sota
AU  - Jan Strobl
AU  - Hira Waseem
AU  - Siyu Wu
PY  - 2026
DA  - 2026/10/28
JO  - The Astrophysical Journal Letters
DO  - 10.3847/2041-8213/aea990
UR  - https://iopscience.iop.org/article/10.3847/2041-8213/aea990
AB  - We present a multiwavelength study of GRB 260310A, a nearby long-duration gamma-ray burst (GRB) at z ≃ 0.153 associated with a broad-lined Type Ic supernova. Despite its modest prompt gamma-ray output, E γ ,iso ≃ 3.5 × 10 ⁵⁰ erg, GRB 260310A exhibits one of the brightest afterglows ever observed in the X-ray, optical, and radio bands. Its apparent brightness is not its only remarkable feature. The optical afterglow displays a delayed onset, characterized by a slow rising phase, with slope α ≈ −1, and a late peak at ∼0.1 day. We argue that the combination of weak prompt emission, hard peak energy, and late afterglow onset is naturally explained by a GRB jet viewed off-axis. The radio spectral energy distributions are consistent with synchrotron radiation and indicate the presence of both reverse- shock (RS) and forward-shock (FS) components, thus providing a first test of RS models in an off-axis geometry. The X-ray afterglow displays a prominent rebrightening, monitored for up to ∼68 days with no evidence of spectral evolution. A low level of linear polarization, Π ≈ 1.7%, is measured at 15 GHz at T ₀ + 55 days and suggests that, at these late times, the FS is the dominant emission component from radio to X-rays. This late-time rebrightening represents a critical test for the two-component jet model. If interpreted as the emergence of a narrow jet core viewed further off-axis, it would imply extreme luminosities and energetics for an on-axis observer.
SN  - 2041-8213
SN  - 2041-8205
ER  -