Transcripts of 13886_Fizzled_GRB_1080

[Music throughout] NASA’s Fermi Gamma-ray Space Telescope has spotted the shortest burst of gamma rays ever seen from a collapsing star. It challenges the traditional classification of gamma-ray bursts, also called GRBs. Short GRBs – those lasting less than 2 seconds – are thought to occur when orbiting objects like neutron stars spiral together and merge. Longer bursts come from massive stars at the ends of their lives. A black hole forms at the center of the collapsing star. It drives long-lasting jets that drill through the star, producing gamma rays when they emerge. The star then transforms into a supernova. On August 26, 2020, Fermi detected a GRB lasting about 1 second. Instruments on other spacecraft saw it too, including NASA’s Wind and Mars Odyssey missions. They helped narrow down the location to a patch of sky in the constellation Andromeda. Less than a day after the GRB, astronomers identified a fading source of visible light using the Zwicky Transient Facility at Palomar Observatory. This was the burst’s afterglow. NASA’s Swift satellite soon recorded X-rays from it, and within days, ground-based radio telescopes observed it too. After a few weeks, when the afterglow had decayed, ground-based observatories confirmed the presence of a brightening supernova. This means the GRB must have come from a massive collapsing star, not a merger. Astronomers think this burst, called GRB 200826A, was on the verge of not occurring at all. About 6.6 billion years ago, a massive star in a distant galaxy reached the end of its life. Its core collapsed and formed a black hole, which launched near-light-speed particle jets through the star. But just as they breached the surface, the jets shut down, producing a surprisingly brief GRB. Astronomers think it’s likely some short GRBs they’ve detected are misclassified as mergers when, instead, they’re really bursts from jets that nearly failed to drill through collapsing stars. We only detect GRBs when the jets aim in our direction. Even accounting for this, long GRBs still occur at a lower rate than the supernova type associated with them. This means most collapsing massive stars likely fail to produce long-lived jets – dying, at least from the gamma-ray perspective, with a whimper instead of a bang. [NASA]