Massive stars usually end their lives in supernova explosions, ejecting energy and mass into space. However, this new research indicates that with enough mass, a star's gravitational pull can be so strong that it collapses directly into a black hole without an explosion.

"We believe that the core of a star can collapse under its own weight, as happens to massive stars in the final phase of their lives. But instead of the contraction culminating into a bright supernova explosion that would outshine its own galaxy, expected for stars more than eight times as massive as the Sun, the collapse continues until the star becomes a black hole," said Alejandro Vigna-Gomez, first author of the study.

This research is linked to the phenomenon of disappearing stars, providing a plausible explanation for such events. Vigna-Gomez added, "The results we have obtained from analysing VFTS 243 has brought us much closer to a credible explanation."

The study analyzed VFTS 243, a binary system with a star and a black hole roughly 10 times more massive than our Sun. Despite the presence of a black hole, there are no signs of a supernova explosion. "The orbit of the system has barely changed since the collapse of the star into a black hole," explained Vigna-Gomez.

Professor Irene Tamborra, who also participated in the study, noted that the system provides a benchmark for future research into stellar evolution and collapse. "Our results highlight VFTS 243 as the best observable case so far for the theory of stellar black holes formed through total collapse, where the supernova explosion fails and which our models have shown to be possible. It is an important reality check for these models. And we certainly expect that the system will serve as a crucial benchmark for future research into stellar evolution and collapse."

The researchers found no significant "natal kick," an acceleration expected from a supernova, and the orbit of VFTS 243 remains nearly circular. "This again indicates the absence of an explosion," said Vigna-Gomez.

The analysis suggests that the energy during the stellar collapse was mainly lost via neutrinos, which interact very weakly. This provides further evidence that the system did not experience an explosion.

The phenomenon of disappearing stars has been observed in modern times, with efforts like "A Survey about Nothing" led by astrophysicist Chris Kochanek seeking to understand these events. Historical descriptions also hint at such occurrences, including myths like that of the Pleiades star cluster.

Research Report:Constraints on Neutrino Natal Kicks from Black-Hole Binary VFTS 243

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University of Copenhagen - Faculty of Science
Stellar Chemistry, The Universe And All Within It