“The capability to quickly direct the Blanco and Gemini telescopes at very short notice is essential for observing transient phenomena such as gamma ray bursts,” said a graduate researcher at a U.S. university.
This statement reflects the pursuit of GRB 250702B, an extraordinary gamma ray burst that broke existing records. Rather than a brief flash lasting seconds or minutes, the event flared multiple times and continued to release high energy radiation for over seven hours.
An early turning point came from infrared data collected by a major ground based telescope, which confirmed that the event originated outside the Milky Way.
The research team focused on the afterglow, the light that gradually fades after the initial gamma flash.
The way brightness changes over time provides clues about the explosion itself and the environment in which it occurred.
To do this, the researchers used three of the most powerful ground based telescopes in the world. The instruments tracked the event starting about fifteen hours after its discovery and continued observations for roughly eighteen days.
The observations were gathered using a range of essential instruments, including an infrared camera, a high-resolution optical camera, and spectrographs attached to the telescopes. The results were subsequently published in a peer-reviewed scientific journal.
The analysis showed that the event was barely visible in optical light.
Some of the obscuration comes from interstellar dust in the Milky Way, but most of it originates in the host galaxy itself, which is extremely rich in dust.
One of the telescopes required nearly two hours of observation time to extract a faint signal buried beneath thick layers of dust.
The researchers integrated these measurements with fresh observations from another major telescope, along with publicly accessible data from space-based observatories and X-ray and radio facilities. They then analyzed the complete dataset against theoretical models to determine which scenarios could account for a burst that persisted for several hours.
According to the analysis, the initial signal was most likely produced by a very narrow and extremely fast, dust rich environment around the explosion site and an unusually massive host galaxy compared to most known gamma ray burst galaxies.
It is possible that the source lies behind a thick dust lane within the galaxy, directly along our line of sight, which would explain the need for infrared observations and long exposure times.
Out of approximately fifteen thousand gamma ray bursts observed since 1973, only about half a dozen come close to the extreme duration of GRB 250702B.
Even so, it does not fit neatly into any known category.
Several possible explanations are currently under consideration.
Among them are a scenario in which a black hole plunges into a hydrogen stripped star composed almost entirely of helium,
disruption of a star by an intermediate mass black hole with a mass between one hundred and one hundred thousand times that of the Sun.
At this stage, additional observations are needed to decide between the possibilities, but the data collected so far are consistent with these new scenarios.
“This is a problem of cosmic archaeology,” the researcher concluded.
“We are reconstructing an event that occurred billions of light years away.”