A suspected supernova is actually something rarer

In a case of comic false identity, an international team of astronomers has revealed that what they once thought was a supernova is actually periodically flaring up from a galaxy where a supermassive black hole emits energy every 114 days as it tear off pieces of an orbit. star.

Six years after its initial discovery – reported in The Astronomer’s Telegram by Carnegie’s Thomas Holoien – researchers, led by Anna Payne of the University of Hawaii in Manao, can now say that the phenomenon they observed, called ASASSN-14ko, periodically is a recurring torch from the center of a galaxy more than 570 million light-years away in the southern constellation Pictor.

Their findings – based on 20 cases of frequent eruptions – will be Astrophysical Journal and presented by Payne at the annual meeting of the American Astronomical Society.

Active galaxies, such as the host ASASSN-14ko, have extremely bright and variable centers. These objects produce much more energy than the combined contribution of all their stars. Astrophysicists believe this is due to gravity and frictional forces that heat up a swirling gas and dust disk that accumulates around the central supermassive black hole. The black hole digests the material slowly, causing low-level, random changes in the light emitted by the disk.

This is the first unambiguous example of such clockwork behavior from an active galaxy. Periodic recurring torches, such as those of ASASSN-14ko, may be evidence of observantly elusive cosmic phenomena previously predicted by theorists.

“If we know the roster of this extragalactic Old Faithful, we can coordinate and study it in more detail,” Payne said.

ASASSN-14ko was first detected by the All-Sky Automated Survey for Supernovae (ASAS-SN), a global network of 20 robotic telescopes headquartered at Ohio State University (OSU) in Columbus. When Payne examined all the ASAS-SN data on the phenomenon, she noticed a series of 17 torches that were regularly spaced apart.

Based on this discovery, astronomers predicted that the galaxy would erupt again on May 17 last year and coordinate ground- and space-based facilities to make observations. They meanwhile successfully showed and saw predictions on 7 September and 26 December.

“ASAS-SN is designed to explore the physics of our universe by looking for transient and variable events.” Holoien said. “It’s exciting that the bright object we originally thought was a violent supernova explosion – which on its own would be interesting, but more common – turns out to be a very coveted cosmic event.”

What causes the repeated torches? The team has considered several possible explanations, but thinks the most likely is a partial tide disruption event.

Tide disruption events, or TDEs, occur when a star gets too close to a supermassive black hole that tears it to shreds. Some of the material is thrown into space and the rest falls on the black hole again and forms a disk with hot, clear gas while it is being consumed.

In this case, instead of a star being erased by interacting with the black hole, it will be slowly removed during each orbit. The torches occur when the lost material – equal to three times the mass of Jupiter at each pass – falls in the direction of the black hole.

The astronomers are not sure how long the torches will last. The star cannot lose mass forever, and although scientists can estimate the amount of mass it loses during each orbit, they do not know how much it originally had.

“We plan to predict and observe these eruptions, or for as long as we can,” said second author Benjamin Shappee, also of UH Mānoa (and an alumnus of Carnegie). “This rare find could reveal new details about physics in black holes.”