A Stellar Collision Triggers a Supernova Explosion

By Ngoma Manuel Astrofísica, Astronomía Estelar Comentarios desactivados

Fast-moving debris from a supernova explosion triggered by a stellar collision crashes into material thrown out earlier, and the shocks cause bright radio emission seen by the VLA. Credit: Bill Saxton, NRAO/AUI/NSF

Astronomers have found remarkable evidence that a great void or neutron star spiraled its way right into the core of a buddy star as well as triggered that buddy to take off like a supernova. The astronomers were tipped off by information from the Very Large Selection Sky Survey (VLASS), a multi-year job using the National Scientific research Structure’s Karl G. Jansky Huge Variety (VLA).

“Theorists had forecasted that this might happen, yet this is the very first time we’ve seen such an occasion”

Said Dillon Dong, a graduate student at Caltech as well as lead author on a paper reporting the discovery in the journal Science.

The initial hint was revealed when the researchers looked at photos from VLASS, which began observing in 2017, and discovered objects that were spectacularly generating radio waves but had not been seen in an earlier VLA sky survey dubbed Faint photos of the Radio Skies at Twenty Centimeters (FIRST).

The information from all these monitorings allowed the astronomers to assemble the remarkable history of a centuries-long death dance between two massive stars. Like many stars that are much larger than our Sun, these two were birthed as a binary pair, closely orbiting each other. Among them was more substantial than the other and advanced through its regular, nuclear fusion-powered lifetime quicker as well as took off like a supernova, leaving behind either a significant void or a superdense neutron celebrity.

The Sequence of Events — Clockwise, from top left: (1.) A neutron star or black hole orbits a “normal” companion star (light blue), growing closer over thousands of years. (2.) The neutron star or black hole enters its companion’s atmosphere, throwing gas outward in an expanding spiral. (3.) When the intruder reaches the companion’s core, material briefly forms a disk that propels a superfast jet outward, poking its way out of the star. The nuclear fusion that held the companion’s core up against its own gravity is disrupted, triggering a collapse and subsequent supernova explosion. (4.) The material blasted out by the supernova explosion catches up to the material thrown out by the earlier interaction, causing strong shock waves that produce the radio waves observed with the VLA. Credit: Bill Saxton, NRAO/AUI/NSF

The great void or neutron star’s orbit expanded steadily closer to its friend, and about 300 years ago, it got in the buddy’s ambiance, beginning the death dance. Now, the interaction started spraying gas away from the companion into the room. The expelled gas, spiraling external, created an increasing, donut-shaped ring, called a torus, around both.

Ultimately, the great void or neutron star made its means internal to the buddy celebrity’s core, disrupting the nuclear fusion generating the power that kept the core from collapsing of its gravity. As the core fell, it quickly formed a disk of material very closely orbiting the burglar and pushed a jet of material outside from the disk at rates coming close to that of light, drilling its way with the star.

A compact object (a black hole or neutron star) at the core of its massive stellar companion. Rapid accretion onto the compact object has caused it to form an accretion disk and launch a pair of jets at nearly the speed of light. Those jets have tunneled through the star, which is about to explode in a supernova due to the enormous amount of energy released. In the next few years, the exploded stellar material will plow its way through a dense torus of stellar material ejected by the compact object during its previous centuries of inspiral towards the core, creating a luminous radio afterglow. Credit: Chuck Carter

“That jet is what generated the X-rays seen by the MAXI tool aboard the International Space Station, and also this validates the date of this occasion in 2014,” Dong said.

The collapse of the celebrity’s core caused it to take off like a supernova, following its sibling’s earlier explosion

Dong asserted that although the buddy celebrity was most likely to become popular someday, the merger hastened the process.

Through the time VLASS observed the object, the supernova blast was colliding with that product, producing enough shocks to generate the bright radio emission seen by the VLA. The material ejected by the 2014 supernova surge moved much faster than the material thrown off earlier from the buddy famous people.

“All the items of this problem fit together to inform this fantastic story,” claimed Gregg Hallinan of Caltech. “The remnant of a celebrity that exploded a very long time ago plunged into its buddy, creating it, as well, to blow up,” he included.

Hallinan stated that the secret to the exploration was VLASS, which is imaging the whole skies noticeable at the VLA’s latitude – about 80 percent of the sky – 3 times over seven years. One of the purposes of doing VLASS is to uncover transient things, such as supernova explosions, that give off vibrantly at radio wavelengths. This supernova, caused by a stellar merger, nevertheless, was a surprise.

“Of all things we believed we would certainly discover with VLASS, this was not one of them,” Hallinan said.

Reference: D. Z. Dong et al, A transient radio source consistent with a merger-triggered core collapse supernova, Science (2021). DOI: 10.1126/science.abg6037