Theorists have predicted the first observation of a completely new type of supernova, but it has not been confirmed before.

In 2017, a bright and unusual source of radio waves was discovered in data captured by the Very Large Array Sky Survey (VLA), a project that scans the night sky with radio wavelengths. Now, led by Caltech graduate student Dillon Dong (MS ’18), a team of astronomers has determined that the bright radio glow was caused by Calabozo or neutron star colliding with its companion star in an unprecedented process.

“Massive stars generally explode as supernovae when their nuclear fuel runs out,” says Greg Hallinan, professor of astronomy at Caltech. “But in this case, a gaseous black hole or neutron star caused its companion star to explode prematurely.” This is the first time that a supernova explosion caused by a merger has been confirmed.

An article on the results has been published in the journal. Science September 3, 2021.

Shine in the night sky
Hallinan and his team search for so-called radio transients, sources of short-lived radio waves that glow brightly and burn quickly like a match in a dark room. Radio transmitters are a great way to identify unusual astronomical events, such as massive stars exploding and releasing jets of energy or neutron star mergers.

As Dillon Dong examined the huge VLA dataset, he chose a very bright source of radio waves from the VLA survey called VT 1210 + 4956. This source is associated with the brightest radio transient associated with a supernova.

Dong determined that the bright radio energy was originally a star surrounded by a thick, dense crust of gas. This gaseous shell had been thrown from the star a few hundred years before today. VT 1210 + 4956, Radio Transient, occurred when the star finally exploded in a supernova and the material released by the explosion interacted with the gas envelope. However, the gas projectile itself and the timeline in which it was launched from the star were unusual, so Dong suspected that there might be more to the story of this explosion.

Two unusual events

After Dong’s discovery, Caltech graduate student Anna Ho (PhD ’20) suggested that this radio transit be compared to a different rate of brief bright events in the X-ray spectrum. Some X-ray events were so short lived that They only existed in the sky for a few seconds of Earth’s time. By examining this other catalog, Dong discovered an X-ray source that originated from the same place in the sky as VT 1210 + 4956. Through careful analysis, Dong showed that the X-rays and radio waves were probably coming from the same event.