Explanipedia

Unveiling the nature of the Einstein Probe transient EP 241021a Open

J. Quirola-Vásquez, P. G. Jonker, A. J. Levan, D. Malesani, F. E. Bauer , et al. · 2025

We present a multi-wavelength analysis of the fast X-ray transient EP 241021a, discovered by the Wide-field X-ray Telescope aboard the Einstein Probe satellite on 2024 October 21. The event was not detected in gamma-rays. Follow-up observa…

Unveiling the nature of the Einstein Probe transient EP 241021a Open

J. Quirola-Vásquez, P. G. Jonker, A. J. Levan, D. Malesani, Nikhil Sarin , et al. · 2025

We present a multi-wavelength analysis of the fast X-ray transient EP 241021a, discovered by the Wide-field X-ray Telescope aboard the \emph{Einstein Probe} satellite on 2024 October 21. The event was not detected in gamma-rays. Follow-up …

EP250207b is not a collapsar fast X-ray transient. Is it due to a binary compact object merger? Open

P. G. Jonker, A. J. Levan, Xing Liu, A. De, Yuan Liu , et al. · 2025

Fast X-ray Transients (FXTs) are short-lived extra-galactic X-ray sources. Recent progress through multi-wavelength follow-up of Einstein Probe discovered FXTs has shown that several are related to collapsars, which can also produce γ-ray …

The Radio Flare and Multiwavelength Afterglow of the Short GRB 231117A: Energy Injection from a Violent Shell Collision Open

G. E. Anderson, Gavin P. Lamb, B. P. Gompertz, Lauren Rhodes, A. Martín-Carrillo , et al. · 2025

We present the early radio detection and multiwavelength modeling of the short gamma-ray burst (GRB) 231117A at redshift z = 0.257. The Australia Telescope Compact Array automatically triggered a 9 hr observation of GRB 231117A at 5.5 and …

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

Amit Kumar, B. P. Gompertz, Benjamin Schneider, S. Belkin, Makenzie E. Wortley , et al. · 2025

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 afterglow…

The most distant optically polarised GRB afterglow: GRB 240419A at z = 5.178 Open

R. Brivio, S. Covino, M. Ferro, A. Saccardi, A. Martín-Carrillo , et al. · 2025

Context. Gamma-ray bursts (GRBs) are extremely bright phenomena powered by relativistic jets arising from explosive events at cosmological distances. The nature of the jet and the configuration of the local magnetic fields are still unclea…

JWST Spectroscopy of GRB 250702B: An Extremely Rare and Exceptionally Energetic Burst in a Dusty, Massive Galaxy at $z=1.036$ Open

B. P. Gompertz, A. J. Levan, T. Laskar, Benjamin Schneider, A A Chrimes , et al. · 2025

We present follow-up observations of the day-long, repeating GRB 250702B with the Near Infrared Spectrograph (NIRSpec) on board the James Webb Space Telescope (JWST). Through the identification of narrow hydrogen emission lines at a consis…

GRB 241105A: a test case for GRB classification and rapid r -process nucleosynthesis channels Open

Dimple Dimple, B. P. Gompertz, A. J. Levan, D. Malesani, T Laskar , et al. · 2025

Gamma-ray bursts (GRBs) offer a powerful window to probe the progenitor systems responsible for the formation of heavy elements through the rapid neutron capture (r-) process, thanks to their exceptional luminosity, which allows them to be…

Discovery and Analysis of Afterglows from Poorly Localised GRBs with the Gravitational-wave Optical Transient Observer (GOTO) All-sky Survey Open

Amit Kumar, B. P. Gompertz, Benjamin Schneider, S. Belkin, Makenzie E. Wortley , et al. · 2025

Gamma-ray bursts (GRBs), particularly those detected by wide-field instruments such as the Fermi/GBM, pose a challenge for optical follow-up due to their large initial localisation regions, leaving many GRBs without identified afterglows. …

The Day-long, Repeating GRB 250702B: A Unique Extragalactic Transient Open

A. J. Levan, A. Martín-Carrillo, T. Laskar, R. A. J. Eyles-Ferris, Albert Sneppen , et al. · 2025

γ -ray bursts (GRBs) are singular outbursts of high-energy radiation with durations typically lasting from milliseconds to minutes and, in extreme cases, a few hours. They are attributed to the catastrophic outcomes of stellar-scale events…

The radio flare and multi-wavelength afterglow of the short GRB 231117A: energy injection from a violent shell collision Open

G. E. Anderson, Gavin P. Lamb, B. P. Gompertz, L. Rhodes, A. Martín-Carrillo , et al. · 2025

We present the early radio detection and multi-wavelength modeling of the short gamma-ray burst (GRB) 231117A at redshift $z=0.257$. The Australia Telescope Compact Array automatically triggered a 9-hour observation of GRB 231117A at 5.5 a…

Spectral Hardening Reveals Afterglow Emergence in Long-duration Fast X-Ray Transients: A Case Study of GRB 250404A/EP250404a Open

Yi-Han Iris Yin, Y Fang, Bin‐Bin Zhang, Chen Deng, Jun Yang , et al. · 2025

The prompt emission and afterglow phases of gamma-ray bursts (GRBs) have been extensively studied, yet the transition between these two phases remains inadequately characterized due to limited multiwavelength observational coverage. Among …

The day-long, repeating GRB 250702BDE / EP250702a: A unique extragalactic transient Open

A. J. Levan, A. Martín-Carrillo, T. Laskar, R. A. J. Eyles-Ferris, Albert Sneppen , et al. · 2025

Gamma-ray bursts (GRBs) are singular outbursts of high-energy radiation with durations typically lasting from milliseconds to minutes and, in extreme cases, a few hours. They are attributed to the catastrophic outcomes of stellar-scale eve…

EP240801a/XRF 240801B: An X-Ray Flash Detected by the Einstein Probe and the Implications of Its Multiband Afterglow Open

Shuai-Qing Jiang, D. Xu, Agnes P.C van Hoof, Wei‐Hua Lei, Yuan Liu , et al. · 2025

We present multiband observations and analysis of EP240801a, a low-energy, extremely soft gamma-ray burst (GRB) discovered on 2024 August 1 by the Einstein Probe (EP) satellite with a weak contemporaneous signal also detected by the Fermi …

EP 250108a/SN 2025kg: Observations of the Most Nearby Broad-line Type Ic Supernova Following an Einstein Probe Fast X-Ray Transient Open

Jillian Rastinejad, A. J. Levan, P. G. Jonker, C. D. Kilpatrick, Chris L. Fryer , et al. · 2025

With a small sample of fast X-ray transients (FXTs) with multiwavelength counterparts discovered to date, their progenitors and connections to γ -ray bursts (GRBs) and supernovae (SNe) remain ambiguous. Here, we present photometric and spe…

The Kangaroo’s First Hop: The Early Fast Cooling Phase of EP250108a/SN 2025kg Open

R. A. J. Eyles-Ferris, P. G. Jonker, A. J. Levan, D. Malesani, Nikhil Sarin , et al. · 2025

Fast X-ray transients are a rare and poorly understood population of events. Previously difficult to detect in real time, the launch of the Einstein Probe with its Wide-field X-ray Telescope has led to a rapid expansionof the sample and al…

GRB 241030A: Multicomponent Origin of Early Emission from the Photosphere and Internal and External Shocks Open

Qingyuan Wang, Hao Zhou, Yun Wang, Jia Ren, Samaporn Tinyanont , et al. · 2025

We present a detailed analysis of the long-duration GRB 241030A detected by Swift. Thanks to the rapid response of the X-Ray Telescope (XRT) and Ultraviolet/Optical Telescope, the strongest part of the prompt emission of GRB 241030A has be…

The Einstein Probe Transient EP240414a: Linking Fast X-Ray Transients, Gamma-Ray Bursts, and Luminous Fast Blue Optical Transients Open

Joyce N.D van Dalen, A. J. Levan, P. G. Jonker, D. Malesani, L. Izzo , et al. · 2025

Detections of fast X-ray transients (FXTs) have accrued over the last few decades. However, their origin has remained mysterious. Rapid progress is now being made thanks to timely discoveries and localizations with the Einstein Probe missi…

A comprehensive broadband analysis of the high-redshift GRB 240218A Open

R. Brivio, S. Campana, S. Covino, M. Ferro, Giulia Gianfagna , et al. · 2025

Context. The detection and follow-up observations of high-redshift ( z > 6) gamma-ray bursts (GRBs) provide a unique opportunity to explore the properties of the distant Universe. Unfortunately, they are rather rare, with only a dozen of t…

The brightest GRB ever detected: GRB 221009A as a highly luminous event at z = 0.151 Open

D. Malesani, A. J. Levan, L. Izzo, A. de Ugarte Postigo, G. Ghirlanda , et al. · 2025

Context. The extreme luminosity of gamma-ray bursts (GRBs) makes them powerful beacons, thus effective probes of the distant Universe. The most luminous bursts are typically detected at moderate and high redshift, where the volume for seei…

Multiwavelength analysis of AT 2023sva: a luminous orphan afterglow with evidence for a structured jet Open

Gokul P. Srinivasaragavan, D. A. Perley, Anna Y. Q. Ho, Brendan O’Connor, A. de Ugarte Postigo , et al. · 2025

We present multiwavelength analysis of ZTF23abelseb (AT 2023sva), an optically discovered fast-fading ($\Delta m_r = 2.2$ mag in $\Delta t = 0.74$ d), luminous ($M_r \sim -30.0$ mag), and red ($g-r = 0.50$ mag) transient at $z = 2.28$ with…

Contemporaneous optical-radio observations of a fast radio burst in a close galaxy pair Open

K Y Hanmer, Inés Pastor-Marazuela, J. Brink, D. Malesani, B. W. Stappers , et al. · 2025

We present the MeerKAT discovery and MeerLICHT contemporaneous optical observations of the fast radio burst (FRB) 20230808F, which was found to have a dispersion measure of $\mathrm{DM}=653.2\pm 0.4\mathrm{\, pc\, cm^{-3}}$. FRB 20230808F …

GRB 241030A: a prompt thermal X-ray emission component and diverse origin of the very early UVOT WHITE and U band emission Open

Qingyuan Wang, H. Zhou, Yun Wang, Jia Ren, Samaporn Tinyanont , et al. · 2025

We present a detailed analysis of the long-duration GRB 241030A detected by {\it Swift}. Thanks to the rapid response of XRT and UVOT, the strongest part of the prompt emission of GRB 241030A has been well measured simultaneously from opti…

Neutral fraction of hydrogen in the intergalactic medium surrounding high-redshift gamma-ray burst 210905A Open

H. Fausey, S. Vejlgaard, A. J. van der Horst, K. E. Heintz, L. Izzo , et al. · 2024

The Epoch of Reionization (EoR) is a key period of cosmological history in which the intergalactic medium (IGM) underwent a major phase change from being neutral to almost completely ionized. Gamma-ray bursts (GRBs) are luminous and unique…

GRB 211024B: An Ultra-long GRB Powered by Magnetar Open

Shao-Yu Fu, D. Xu, Wei‐Hua Lei, A. de Ugarte Postigo, D. Malesani , et al. · 2024

Ultra-long gamma-ray bursts are characterized by exceptionally long-duration central engine activities, with characteristic timescales exceeding 1000 s. We present ground-based optical afterglow observations of the ultra-long gamma-ray bur…

GRB 211024B: an ultra-long GRB powered by magnetar Open

Shao-Yu Fu, D. Xu, Wei‐Hua Lei, A. de Ugarte Postigo, D. Malesani , et al. · 2024

Ultra-long gamma-ray bursts (ULGRBs) are characterized by exceptionally long-duration central engine activities, with characteristic timescales exceeding 1000 seconds. We present ground-based optical afterglow observations of the ultra-lon…

A Radio Flare in the Long-lived Afterglow of the Distant Short GRB 210726A: Energy Injection or a Reverse Shock from Shell Collisions? Open

Genevieve Schroeder, Lauren Rhodes, T. Laskar, Anya E. Nugent, Alicia Rouco Escorial , et al. · 2024

We present the discovery of the radio afterglow of the short gamma-ray burst (GRB) 210726A, localized to a galaxy at a photometric redshift of z ∼ 2.4. While radio observations commenced ≲1 day after the burst, no radio emission was detect…

Rapid Response Mode observations of GRB 160203A: Looking for fine-structure line variability at z = 3.52 Open

G. Pugliese, A. Saccardi, V. D’Elia, S. D. Vergani, K. E. Heintz , et al. · 2024

Context . Gamma-ray bursts are the most energetic known explosions. Although they fade rapidly, they give us the opportunity to measure redshift and important properties of their host galaxies. We report the photometric and spectroscopic s…

A Hubble Space Telescope Search for r-Process Nucleosynthesis in Gamma-Ray Burst Supernovae Open

Jillian Rastinejad, Wen‐fai Fong, A. J. Levan, N. R. Tanvir, C. D. Kilpatrick , et al. · 2024

The existence of a secondary (in addition to compact object mergers) source of heavy element ( r -process) nucleosynthesis, the core-collapse of rapidly rotating and highly magnetized massive stars, has been suggested by both simulations a…

Soft X-ray prompt emission from a high-redshift gamma-ray burst EP240315a Open

Yong Liu, Hui Sun, D. Xu, D. Svinkin, James DeLaunay , et al. · 2024

Long gamma-ray bursts (GRBs) are believed to originate from core collapse of massive stars. High-redshift GRBs can probe the star formation and reionization history of the early universe, but their detection remains rare. Here we report th…

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