First radio detection of ‘type Ia’ supernova

BY THE INSTITUTE OF ASTROPHYSICS OF ANDALUSIA (IAA-CSIC)

A recent work published in Nature announced the first-ever radio detection of a “type Ia” supernova. The discovery has been possible thanks to observations by the e-MERLIN array in the UK, and data analysis at the Spanish prototype SKA Regional Centre (SPSRC).

Type Ia supernovae occur when a white dwarf, the “corpse” of a Sun-like star, absorbs material from a companion star and reaches a critical mass, around 1.4 solar masses, triggering an explosion with a similar luminosity in almost all cases. This uniformity makes type Ia supernovae ideal for measuring cosmic distances. Nevertheless, until now it was not known whether this companion was another white dwarf or a Sun-like star, something that radio imaging can reveal.

“When we saw signs of a strong interaction with the companion star material in supernova SN2020eyj, we tried to observe the explosion in radio, something that had been attempted without success for decades,” explained Dr Erik Kool from Stockholm University, lead author of the paper.

Now, in this first radio detection of a type Ia supernova, the radio data contribution led by the IAA-CSIC, combined with optical data has confirmed that the material expelled in the supernova explosion collided with the surrounding material, composed mostly of helium, which indicates that the companion star was not a white dwarf.

“This is a milestone that has allowed us to demonstrate that the exploded white dwarf was accompanied by a normal, non-degenerate star before the explosion. In addition, with these observations we can estimate the mass and geometry of the material surrounding the supernova, which allows us to better understand what the system was like before the explosion,” said Dr Javier Moldón, researcher at the IAA-CSIC who participated in the discovery.

Artist’s impression of a type Ia supernova, in which a white dwarf star absorbs material from its companion star.

Credit: Adam Makarenko/W. M. Keck Observatory.

“The unusual light curve of SN 2020eyj, the infrared emission, the detection of helium emission lines and the unprecedented radio detection make this supernova unique, a treasure trove of information with implications for multiple fields of research,” said Dr Miguel Pérez Torres, IAA-CSIC researcher participating in the study.

“Now that we have shown that radio observations can provide direct and unique information to understand this type of supernovae, it opens a path to study these systems with the new generation of radio instruments, such as the SKA telescopes in the future,” added Dr Moldón.

e-MERLIN is the UK’s national radio telescope interferometer headquartered at Jodrell Bank Observatory and operated by the University of Manchester on behalf of the Science & Technology Facilities Council. The SPSRC is located in the Institute of Astrophysics of Andalusia (IAA-CSIC) and supports preparatory scientific activities for future SKA projects while promoting Open Science practices.