Although massive stars usually die with spectacular explosions, a handful fizzle out like dud firecrackers.
Astronomers have identified the remnants of one such dud firecracker in SGR 0755-2933, a neutron star about 11,400 light-years from Earth in the southern constellation of Puppis. In new research, scientists say that earlier in its lifetime, this star transferred abnormally high amounts of mass to its binary companion — so much so that it was not left with enough material for an explosive death. Instead, it ended in a quiet “ultra-stripped” supernova, a rare cosmic event that leaves a super-dense remnant called a neutron star in its wake.
“This remarkable binary system is essentially a one-in-10-billion system,” André-Nicolas Chené, an astronomer at the National Science Foundation’s NOIRLab research center and a co-author of the new study, said in a statement.
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The neutron star and its closely orbiting binary companion — a star that the researchers also predict will someday collapse to become a neutron star — mark the first clear example of a star system that will ultimately trigger a kilonova, a cosmic explosion during which two neutron stars merge.
Although a kilonova was first detected in 2017, astronomers then recorded only the aftermath of the event, thanks to observations of light and gravitational waves. The new research is the first time scientists have identified a binary star system that they know will end in a kilonova explosion.
Moreover, astronomers previously thought that only one or two such systems would exist in spiral galaxies like our Milky Way. Researchers of the latest study have now increased that estimate to 10, noting that these observations help them better understand the history, evolution and atypically calm deaths of stars in such systems.
“For quite some time, astronomers speculated about the exact conditions that could eventually lead to a kilonova,” Chené said in the statement. “These new results demonstrate that, in at least some cases, two sibling neutron stars can merge when one of them was created without a classical supernova explosion.”
The sibling star is massive, orbits the primary neutron star every 60 days, and has a name like a license plate:…
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