NASA Detects Unprecedented Gamma-ray Burst GRB 250702B, Challenging Existing Astrophysical Models

On July 2, 2025, NASA's Fermi Gamma-ray Space Telescope detected an unprecedented gamma-ray burst (GRB), designated GRB 250702B, which exhibited repeated outbursts over nearly a full day—marking it as one of the longest-duration GRBs ever observed.

Gamma-ray bursts are the universe's most energetic explosions, typically lasting from milliseconds to several minutes. They are generally classified into two categories:

• Short-duration GRBs: Lasting less than 2 seconds, often associated with the merger of compact objects like neutron stars.
• Long-duration GRBs: Lasting more than 2 seconds, usually linked to the collapse of massive stars.

GRB 250702B challenges these classifications with its extraordinary duration and repeated outbursts. The Fermi Gamma-ray Burst Monitor (GBM) triggered four times on July 2, 2025, detecting gamma-ray emissions from a similar region of the sky over an interval of approximately 11.5 hours. These events were initially designated as GRB 250702B, C, D, and E. Subsequent analysis suggested that GRB 250702C was an unrelated short GRB, while GRBs 250702B, D, and E likely originated from the same source, now collectively referred to as GRB 250702B. (gcn.nasa.gov)

The Fermi GBM team reported the detection of GRB 250702B at 13:56:05 UT on July 2, 2025, with an on-ground calculated location of RA = 286.0°, Dec = -8.7° (J2000), and a statistical uncertainty of 7.8 degrees. (gcn.nasa.gov) The GBM light curve consisted of multiple pulses with a duration (T90) of about 54 seconds in the 50-300 keV range. (gcn.nasa.gov)

Initial observations suggested the event originated within the Milky Way. However, subsequent imaging by the Very Large Telescope (VLT) and confirmation by the Hubble Space Telescope pinpointed its source in a distant galaxy. (eso.org)

The unique characteristics of GRB 250702B challenge existing astrophysical models. Traditional explanations for long-duration GRBs, such as the collapse of massive stars or tidal disruption events involving black holes, do not fully account for the observed properties. One hypothesis considers the possibility of a white dwarf being disrupted by an intermediate-mass black hole, a scenario that remains poorly understood. (cadenaser.com)

The discovery of GRB 250702B has significant implications:

• Advancement in Astrophysics: Understanding such an unprecedented event could lead to new insights into the life cycles of stars and the behavior of black holes.
• Technological Development: The need to observe and analyze such events may drive advancements in telescope technology and data analysis methods.
• Public Interest: Events like GRB 250702B capture public imagination, potentially increasing interest and funding in space research.

GRB 250702B represents a groundbreaking discovery in astrophysics, challenging existing models and prompting a reevaluation of our understanding of gamma-ray bursts. Ongoing and future observations are crucial to unraveling the mysteries of this extraordinary event.