Breakthrough observations by a Cornell-led team reveal the high-energy flares that repeatedly arise from stellar corpses after they explode, challenging existing theories of stellar death and highlighting the role that black holes or neutron stars may play in this rare, intense phenomenon. The explosive death of a distant star left behind an active stellar corpse believed to be the source of multiple high-energy flares detected over several months.
A Cornell University-led research team reports this phenomenon, which astronomers have never seen before, in a recent study published in the journal Nature.
These bright, brief flashes - lasting as little as a few minutes and as powerful as the original explosion 100 days later - appear in the wake of a rare type of stellar catastrophe that researchers have been searching for, called luminous fast blue-light transients (LFBOTs).
Since its discovery in 2018, astronomers have speculated about what might be driving such extreme explosions, which are much brighter than the violent end that massive stars typically undergo but fade away in days rather than weeks. The team believes this previously unknown flare activity, studied by 15 telescopes around the world, confirms that the engine must be the corpse of the star: a black hole or a neutron star.
Unique astronomical event: AT2022tsd
said Anna Y. Q. Ho, assistant professor of astronomy in the College of Arts and Sciences. "This resolves years of debate over what powered such explosions and reveals an unusually direct way to study the activity of a star's corpse."
Ho is lead author of a recently published study where he, along with more than 70 co-authors, helped describe the LFBOT, officially named AT2022tsd and nicknamed the "Tasmanian Devil," and the subsequent pulse of light seen about 1 billion light-years from Earth.
In September 2022, during an all-sky survey conducted at the Zwicky Transient Facility in California, 500,000 changes, or transients, were detected every day.
Then in December 2022, during routine monitoring of the fading explosion, He Jiong and collaborators Daniel Perley of Liverpool John Moores University in the UK and Ping Chen of the Weizmann Institute of Science in Israel gathered to review new observations made and analyzed by Chen Ping - a set of five images, each spanning a few minutes. The first image doesn't show anything, which is to be expected, but the second image finds light, followed by a strong bright spot in the middle frame that quickly disappears.
"No one knew what to say," Ho recalled. "We've never seen anything like this before - so fast and as bright as the original explosion months later - in any supernova or FBOT. We've never seen anything like this before in astronomy."
To further study the sudden brightening, the researchers worked with partners to make observations using more than a dozen other telescopes, including one equipped with a high-speed camera. The team combed through previous data in an effort to rule out other possible light sources. Ho said their analysis conclusively confirmed that there were at least 14 irregular light pulses over the 120-day period, which was likely just a small fraction of the total.
"What's surprising is that instead of gradually dimming, as one would expect, the light source briefly brightens again - again and again, and again, and again. LFBOT is already a weird, bizarre event, so this one is even weirder," she said.
Impact on stellar evolution and cataclysms
Exactly what process is at work - perhaps the black hole ejecting stellar material outward at nearly the speed of light - remains to be studied. Ho hopes the research will advance the long-held goal of mapping the properties of stars during their lives to predict how they die and the types of corpses they produce.
In the case of LFBOTs, rapid rotation or strong magnetic fields are likely key components of their emission mechanisms, Ho said. It's also possible that they aren't supernovae in the traditional sense at all, but are caused by the merger of a star and a black hole.
"What we are seeing may be an entirely different channel for cosmic catastrophe," she said. "This unusual explosion promises new insights into the life cycle of a star, which is typically only seen in snapshots of different stages - star, explosion, remnant - rather than as part of a single system. LFBOT may provide an opportunity to observe stars in their transition to their 'afterlife.'"
"Because this 'body' isn't just sitting there, it's active and doing things that we can detect," Ho said. "We think these flares may have come from one of these newly formed relics, which gives us a way to study their properties when they first formed."
Compiled source: ScitechDaily