Astronomers have achieved a major breakthrough in the study of gamma-ray bursts, the most luminous explosions in the universe, by observing the afterglow of one such event at millimeter and submillimeter wavelengths just 13 minutes after its initial detection. The observation, made possible by a new rapid-response system on the Submillimeter Array (SMA) in Hawaii, marks the first time that scientists have been able to capture these wavelengths so quickly after a gamma-ray burst (GRB) was detected. The findings were published in The Astrophysical Journal Letters.
The event, designated GRB 260127A, was first detected on January 26, 2026, by the Neil Gehrels Swift Observatory satellite, which automatically sent an alert. The entire sequence of follow-up observations unfolded with minimal human intervention. Within 90 seconds, the duty operator was notified, and in less than four minutes, the SMA telescope began moving to initiate observations. The actual observations started 12.6 minutes after the Swift signal, a response time that represents an improvement of about two orders of magnitude over typical response times for telescopes operating at millimeter and submillimeter wavelengths.
Gamma-ray bursts are brief but extraordinarily intense emissions of gamma rays, produced by jets of matter generated during the collapse of massive stars or the merger of compact objects such as neutron stars. The initial explosion is followed by an afterglow that telescopes in X-ray and optical wavelengths have long been able to observe within seconds or minutes. However, instruments operating at millimeter and submillimeter wavelengths have historically arrived with a significant delay, limiting their ability to capture the early evolution of these transient phenomena.
The new rapid-response capability at the SMA changes that paradigm. The system, which operates in a semi-automatic mode, allows the array to alternate between responding to alerts and conducting standard observations, with minimal impact on other scientific programs. The researchers involved in the development of the system expect to further reduce response times to just two to three minutes in the future, while also enabling the serial observation of multiple targets to maintain high productivity.
Garrett Keating, an astrophysicist at the Center for Astrophysics | Harvard & Smithsonian (CfA) and deputy director of the SMA, is the lead author of the paper describing the rapid-response system. Keating described the experience of watching the system work in real time as extraordinary. He noted that being able to react and process data with such speed represents a radical change from the normal operation of the SMA, but was essential for observing a phenomenon where every minute counts. He added that the team learned a great deal from this first complete operational test and believes further reductions in response time are achievable.
The observations of GRB 260127A were also conducted in optical and X-ray wavelengths simultaneously. The SMA successfully identified a source very close to the flares detected at those other wavelengths. Follow-up observations performed two days later showed that the source had faded significantly, reinforcing the conclusion that the SMA had indeed observed the afterglow of a transient event rather than a constant-emission background galaxy.
The successful observation marks the official launch of the SMA Sprints program, formally known as the SMA Sub/millimeter Program to Rapidly Investigate Novel Time-domain Sources. This program is designed to leverage the SMA and its wideband upgrade, called wSMA, to conduct rapid, sensitive, and flexible follow-up observations of transient events in the variable sky. The study of such phenomena falls under the field of time-domain astronomy, which focuses on objects and phenomena that change over time, observing them as they happen and tracking their evolution minute by minute, day by day, or year by year.
This breakthrough is expected to open new avenues for understanding the physics of gamma-ray bursts and other transient events, providing astronomers with a powerful new tool to capture the earliest moments of the most energetic explosions in the cosmos.
