The cosmic burst was detected at millimeter and submillimeter wavelengths with record-breaking speed, with the telescope being pointed at it within minutes of its onset. Previously, such phenomena had not been detected so quickly at these frequencies. This was made possible by a new automated system.
Record-Breaking Response Time
The observatory on Hawaii’s Mauna Kea, known as the Submillimeter Array (SMA), reached a major milestone in the study of variable celestial objects this past January. Scientists at the Harvard-Smithsonian Center for Astrophysics demonstrated for the first time a new capability to rapidly respond to bursts at millimeter and submillimeter wavelengths.
The telescope was pointed at the target just 13 minutes after receiving an automatic alert about the burst, according to phys.org. The results of the demonstration were published in the peer-reviewed journal The Astrophysical Journal Letters.
A Challenging Target for Telescopes
Gamma-ray bursts are among the brightest phenomena in the universe. They are brief but extremely powerful bursts of energy caused by jets formed during the collapse of massive stars or the collision of compact objects, such as neutron stars.
After the initial burst of gamma radiation, an afterglow at longer wavelengths follows. X-ray and optical telescopes have learned to track it within seconds or minutes, while millimeter- and submillimeter-wave telescopes have lagged behind in this observation.
According to NASA, the Swift observatory detects about 100 gamma-ray bursts each year—that is, on average, one every few days. Thanks to SMA’s new speed, researchers are now able to track these events in near real time.
A Chain of Events in Minutes
The Neil Gehrels Swift Observatory detected a gamma-ray burst and automatically sent an alert about the event to the observation network, to which SMA is connected. Next, a new automated response system was triggered.
The operator on duty was notified just 90 seconds after the alert. Four minutes later, the antennas began to point toward the target. Meanwhile, a dedicated data analysis program generated an image of the burst.
Assessments by the Researchers Involved
The launch of the rapid-response system was led by astrophysicist Garrett Keating, deputy director of SMA. According to him, observing this process in real time was incredibly exciting, as the speed of data processing was radically different from the usual operating mode. He added that the team learned a great deal during this test and hopes to reduce the response time to two to three minutes in the future.
“Interferometry traditionally does not produce direct images from the telescope, so the data must be processed separately and converted into images. Previously, this process took a long time,” explains Ranjani Srinavasan, acting director of the SMA.
Confirmation and Plans for the Future
Follow-up observations two days later showed that the source had faded. This confirmed that the SMA had indeed detected a glow following the explosion, rather than a steady background galaxy. Tanmoy Laskar, a professor of physics and astronomy at the University of Utah and a co-author of the study, noted that this new capability opens a unique window into the physics of some of the most powerful phenomena in the universe.
The successful test marked the start of a new program called the Submillimeter and Millimeter Wave Program for Rapid Investigation of New Transient Sources (SMA SPRINTS). It uses SMA in conjunction with the wSMA broadband upgrade to provide fast, sensitive, and flexible tracking of transient events across the entire sky.
The program was developed in advance to prepare for a new wave of data from future observatories. The Vera Rubin Observatory has already begun its Legacy Survey of Space and Time this summer, and the Roman Space Telescope is set to join the effort later on. Both projects are expected to send millions of alerts about new events in the sky to the astronomical community every day.
