In a case of comically erroneous identity, an international team of astronomers revealed that what they once thought was a supernova is actually periodic burnout from a galaxy, where a supermassive black hole emits energy outbursts every 1
Six years after the first discovery – reported in The Astronomer’s Telegram by Carnegie’s Thomas Holoien – researchers led by Anna Payne of the University of Hawai’i in Mānoa can now say that the phenomenon they observed, called ASASSN-14ko, is periodic. recurring flare 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 regular outbreaks – will be published in Astrophysical journal and presented by Payne at the annual meeting of the American Astronomical Society.
Active galaxies, such as the host ASASSN-14ko, have unusually bright and variable centers. These objects produce much more energy than the total contribution of all their stars. Astrophysicists believe this is due to gravity and frictional forces that heat up a swirling disk of gas and dust that accumulates around the central supermassive black hole. The black hole slowly consumes the material, creating random low-level changes in the light from the disc.
This is the first unambiguous example of such a clockwork from an active galaxy. Periodically recurring flares, such as those from ASASSN-14ko, could be signs of observationally elusive cosmic phenomena that theorists have previously predicted.
“Knowing the schedule of this extra-galactic Old Faithful allows us to coordinate and study it in more detail,” Payne said.
ASASSN-14ko was first discovered 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 flashes at regular intervals.
Based on this discovery, astronomers predicted that the galaxy would experience another eruption on May 17 last year and coordinated Earth- and space-based facilities to make observations. They have since successfully predicted and witnessed flares on September 7th and December 26th.
“ASAS-SN is designed to study the physics of our universe by looking for transient and variable events.” Said Holoien. “It’s exciting that the luminous object, which we originally thought was a violent supernova explosion – which in itself would be interesting, but more common – turned out to be a sought-after cosmic event.”
So what causes the repeated flares? The team considered several possible explanations, but thinks the most likely is what is called a partial tidal disturbance event.
Tide disturbance events or TDEs occur when a star gets too close to a supermassive black hole that tears it to pieces. Some of its material is thrown into space, and the rest falls back onto the black hole, forming a disk of hot, light gas when consumed.
In this case, instead of a star being erased by interaction with the black hole, it was slowly removed during each orbit. The glare occurs when the lost material – equivalent to three times the mass of Jupiter at each pass – falls towards the black hole.
Astronomers are unsure how long the apertures will last. The star cannot lose mass forever, and while scientists can estimate the amount of mass it loses during each orbit, they do not know how much it originally had.
“We plan to continue predicting and observing these eruptions, or for as long as we can,” said co-author Benjamin Shappee, also from UH Mānoa (and a Carnegie alumnus). “This rare find could reveal new details about black hole physics.”
NASA missions help explore an ‘Old Faithful’ active galaxy
ASASSN-14ko is a periodic nuclear transient in ESO 253 – G003. arXiv: 2009.03321 [astro-ph.HE] arxiv.org/abs/2009.03321
Provided by the Carnegie Institution of Science
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