Follow Us Add us as a preferred source on Google Newsletter Subscribe to our newsletter Astronomers have detected a remarkable gamma ray burst (GRB) that is a true Incredible Hulk compared to other cosmic explosions of the same type. What makes this GRB so special is the fact that the central engine that powers it remained active for approximately 27 days, emitting X-rays after the initial explosion. This is 20 days longer than the previous longest GRB on record. This record-breaking explosion, designated GRB 220706A and detected on July 6, 2022, is even more exciting because scientists don’t know what the central engine driving it actually is. first few days after we detected the explosion,” study team member Benjamin Gompertz, from the University of Birmingham in England, told Space.com. “The fact that we see an eruption around 27 days into the resting frame of the GRB tells us that there is an active process going on, and that is unprecedented in the known population,” Gompertz added. “The previous record for delayed burning was about six days after the GRB.” You may like What created the Incredible Hulk of explosions? Gamma-ray bursts? GRBs are some of the most powerful bursts in the cosmos. They have been linked to the collapse of a massive star, which also triggers a supernova and creates a black hole. This results in a long-lived GRB, while short-lived GRBs are thought to be activated when two stellar remnants called neutron stars collide. “We don’t know what the core engine is that drives this burst, and that’s what makes this such a compelling event,” Gompertz said. “The fact that we see a supernova tells us that a star has collapsed, which is the standard energy source for GRBs, but it doesn’t immediately explain the extremely late flare or the unusually bright supernova. We can interpret that through previous events to some extent.” Gompertz added that another ultralong GRB detected in 2011, GRB 111209A, was associated with an unusually bright supernova (SN2011k) that had clear evidence of a central drive. The team behind that research determined that GRB 111209A is driven by a magnetar, a neutron star with a particularly powerful magnetic field. In this case, the magnetic field rotates around 1,000 times per second. “Our supernova looks a lot like this one, so there could be a magnetar here. This fits nicely with superluminous supernovae, which are also thought to be powered by magnetars,” Gompertz said. “Another possibility could be that the GRB jet and supernova are colliding with layers of dense material that were ejected toward the end of the parent star’s life, when it became unstable and began to eject its outer layers. This type of event is also seen in the superluminous supernova population.” What to read next An illustration showing a magnetar surrounded by green magnetic field lines at the heart of a supernova remnant (Image credit: Robert Lea (created with Canva)) The team isn’t quite sure how the core engine of this ultra-long GRB is different from that of others and why that resulted in 27 days of flare. “One possibility is that it is a much larger star than we normally would. “We see producing GRBs,” Gompertz said. “A larger star would take longer to fall in on itself and would therefore provide a longer-lasting energy source to drive the jet.” The sources of GRBs may be members of a stellar population of massive, compact stars called Wolf-Rayet stars. They are 10 times wider than the Sun and about 10 times the mass of our star. However, even the collapse of such a star cannot explain GRB 220706A. “To power GRB 220706A, we estimate that we need a star with a radius more than 1,000 times the radius of the Sun, which would require a population of stars known as blue supergiants,” Gompertz said. “On the other hand, it may be that the remnant is different. If this star produced a magnetar, it may be that ‘normal’ GRBs simply collapse and become black holes.” The team believes the big question with GRBs like this is whether they are members of the normal GRB population or a different type of event. Having this second event, in addition to GRB 111209A, with an unusually bright supernova potentially adds weight to the idea that these are different stars. But the issue is not yet resolved. “The incredibly late flares also put tests our models of how airplanes work,” Gompertz said. “It will be fascinating to see how future theoretical work can incorporate an energy source from a collapsing star that can last a month!” A core-collapsing supernova spawns a black hole and launches a GRB (Image credit: Robert Lea (created with Canva)) There could be even longer-lasting GRBs in the cosmos that we haven’t been able to detect so far. Gompertz explained why these detections are complicated. “GRBs of this length are difficult to detect because most of the satellites we use to find them are in low Earth orbit, which means the target periodically locks on every 90 minutes or so,” he explained. “This is fine for a typical GRB of 10 to 100 seconds duration, but becomes a nuisance when tracking much longer events. Long-lived GRBs also appear to be more active in X-rays than gamma rays.” The University of Birmingham researcher added that recently launched missions like the Einstein probe, which is more sensitive to of the team is presented on the arXiv repository site.
