The unusual death of a star announces the birth of the compact neutron star binary

Anthony Piro of Carnegie was part of a team of astronomers led by Caltech who observed the particular death of a massive star that exploded in a surprisingly weak supernova and which faded quickly, possibly creating a compact binary system of neutron stars. Piro's theoretical work provides a crucial context for discovery. Their results are published by Science.

The observations made by the Caltech team – including lead author Kishalay De and lead investigator Mansi Kasliwal (herself a former Carnegie researcher) – suggest that the dying star had an invisible companion who was siphoning by gravitation most of his mass a supernova. The explosion would have resulted in a neutron star binary, which suggests that, for the first time, scientists witnessed the birth of a binary system similar to the one that was collided by Piro and a team of astronomers from Carnegie and UC Santa Cruz in August 2017.

A supernova occurs when a massive star – at least eight times the mass of the Sun – depletes its nuclear fuel, causing the core to collapse and then rebound to a powerful explosion. After destroying the outer layers of the star, there remains only one dense neutron star, an exotic star the size of a city, but of mass greater than that of the Sun.

Usually, many materials – many times the mass of the Sun – are blown into a supernova. However, the event observed by Kasliwal and his colleagues, baptized iPTF 14gqr, ejected matter only on one-fifth of the Sun's mass.

"We have witnessed the collapse of the nucleus of this massive star, but we have seen a mass mass ejected remarkably low," said Kasliwal. "We call this a supernova-free envelope and have long been predicted that it exists.This is the first time that we have convincingly seen the collapse of the core of the world." a gigantic star devoid of matter. "

The theoretical modeling of Piro guided the interpretation of these observations. This allowed observers to infer the presence of a dense material surrounding the explosion.

"Discoveries like this show why it was so important to create a theoretical astrophysics group in Carnegie," said Piro. "By combining observations and theory, we can learn a lot more about these incredible events."

The fact that the star exploded at all implies that it had to contain a lot of material before, otherwise its core would never have become big enough to collapse. But where was the missing mass hidden? The researchers deduced that the mass must have been stolen by a compact star, such as a white dwarf, a neutron star or a black hole.

The neutron star left behind the supernova must be born in orbit with this compact companion. Because this new neutron star and his companion are so close to each other, they will eventually melt into a collision. In fact, the merger of two neutron stars was observed for the first time in August 2017 by Piro and a team of Carnegie and UC Santa Cruz astronomers, and it is thought that such events produce the heavy elements of our universe , such as gold, platinum and uranium. .

The event was first seen at the Palomar Observatory as part of the Palomar Transient Factory (iPTF), a nocturnal study of the sky aimed at looking for transient or short-lived cosmic events, such as than supernovae. Because the iPTF study monitors the sky so closely, the iPTF 14gqr was observed in the very first hours after its explosion. As Earth turned and the Palomar telescope came out of its reach, astronomers from around the world worked together to monitor the iPTF 14gqr system, constantly observing its evolution with a number of telescopes that now form the network. observatories of the world relay of observatories in transit.

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More information:
K. De el al., "A hot and fast super-fast supernova which probably formed a compact neutron binary star" Science (2018). science.sciencemag.org/cgi/doi… 1126 / science.aas8693