GRB 250702B

GRB 250702B

GRB 250702B (circled in red), taken on 3 July with the VLT’s HAWK-I infrared camera
Event type	Gamma ray burst
Right ascension	18h 58m 45.565s
Declination	−7° 52′ 26.42″

GRB 250702B was an ultra-long duration gamma-ray burst (GRB) and the longest-duration GRB ever detected. It lasted around a day, hundreds of times longer than most GRBs. ^{[1] [2] [3] [4]} It is also exceptional in that it repeated several times and appeared to be periodic. ^{[1] [2]}

Discovery

It was initially detected by the Fermi Gamma-ray Space Telescope on July 2, 2025. ^{[1] [2]} About 10 hours earlier, the Einstein Probe had detected an associated X-ray transient. ^[5]

It was initially believed to have originated inside the Milky Way. A day after the initial detection, the Very Large Telescope showed the source to be extra-galactic; this was later confirmed by the Hubble Space Telescope. ^{[2] [3]}

See also

• GRB 111209A, the second longest lasting GRB at 7 hours

References

1. "Gamma-ray burst explodes in an unusual pattern never seen before". Earth.com. Retrieved 2025-09-11.
2. Dublin, University College. "Unprecedented gamma-ray burst hints at rare black hole". phys.org. Retrieved 2025-09-11.
3. Robert Lea (2025-09-09). "Astronomers discover repeating gamma-ray burst 'unlike anything we have ever witnessed before' (video)". Space. Retrieved 2025-09-11.
4. [e-mail]. "Astronomers spot mysterious gamma-ray explosion, unlike any detected before". www.eso.org. Retrieved 2025-09-11.
5. "GCN - Circulars - 40906 - EP250702a : an X-ray transient detected by Einstein Probe likely associated with GRB 250702B,C,D,E". gcn.nasa.gov. Retrieved 2025-09-11.

Preceded by GRB 111209A

Longest gamma-ray burst 2025 –