First detection of radio waves from the supernova explosion of a white dwarf star

For the first time, it has been possible to capture radio waves emitted by a type Ia supernova, a type of explosion originated by a white dwarf star. This provides important clues to understand how white dwarfs can come to explode.

A type Ia (One-A) supernova is the nuclear explosion of a white dwarf star. This type of supernova is well known; Astronomers use these supernovae to measure great distances in the cosmos and the expansion of the universe. But the explosion mechanism of type Ia supernovae is not fully understood. Lone white dwarfs do not explode, so absorption of matter torn away from a neighboring star is thought to play an essential role in triggering the explosion. The mass stolen by the white dwarf comes from the outer shell of the companion star, so it is normally made mostly of hydrogen, but it was thought that it would also be possible for a white dwarf to absorb helium from a companion star that had lost its outer shell of hydrogen.

As the white dwarf extracts matter from its companion star, some of the material falls on the white dwarf but some forms a cloud around the binary star system. Accepted theory indicates that when a white dwarf supernova explodes and is surrounded by a cloud of material, shock waves from the explosion traveling through the circumstellar material excite the atoms, causing them to emit strong radio waves.

However, while many Type Ia supernovae have been observed exploding within a cloud of circumstellar material, astronomers have not yet observed radio wave emissions associated with a Type Ia supernova until now.

Artist’s impression of the matter transfer process between stars that precedes a Type Ia supernova explosion. (Illustration: Adam Makarenko / WM Keck Observatory)

An international team of researchers, including members of Stockholm University in Sweden and the National Astronomical Observatory of Japan, have made detailed observations of a Type Ia supernova that exploded in 2020.

His work included analyzing data collected by the LRIS (Low Resolution Imaging Spectrometer) spectrometer, installed at the Keck Observatory in Hawaii, United States.

Erik Kool (Stockholm University) and his colleagues have discovered that this supernova was surrounded by circumstellar material composed mainly of helium, and they have also been able to detect radio waves coming from the supernova. Comparison of the intensity of the observed radio waves with theoretical models revealed that the progenitor white dwarf star had been accreting material at a rate of about one-thousandth the mass of the Sun each year. This is the first confirmed Type Ia supernova to be triggered by the absorption of matter stripped away from a companion star with an outer shell made mostly of helium.

It is hoped that this observation of radio waves from a helium-rich type Ia supernova will help to better understand the explosion mechanism and the conditions that precede such a supernova.

The study is titled “A radio-detected Type la supernova with helium-rich circumstellar material”. And it has been published in the academic journal Nature.

Now the team plans to search for radio emissions from other Type Ia supernovae to elucidate the evolution leading to the explosion. (Fountain: NCYT by Amazings)