Type Ia supernovae (SNe Ia) are thermonuclear explosions from degenerate white dwarf stars that have been destabilized by mass accretion from a companion star. However, the nature of their ancestors still needs to be better understood. One way to distinguish between progenitor systems is through radio observations. Despite extensive efforts, no type Ia supernova (SN Ia) has ever been detected at radio wavelengths.
A new study by an international team of researchers, including members from Stockholm University and the National Astronomical Observatory of Japan, reported the discovery of radio waves emitted from a Type Ia supernova. This is the first time astronomers have observed radio waves emitted from a Type Ia supernova, providing crucial clues to understanding how white dwarfs explode.
The team conducted detailed observations of a Type Ia supernova – SN 2020eyj – which exploded in 2020. This supernova was surrounded by circumstellar material composed mostly of helium, as evidenced by its spectral characteristics, infrared emission. To their surprise, scientists were also able to detect radio waves from supernovae.
Based on the modeling, scientists conclude that the circumstellar material likely comes from a singly degenerate binary system in which a white dwarf gathers material from a helium-donor star, a commonly suggested formation channel for SNeIa.
Comparing the observed radio wave strength to theoretical models, it was found that the precursor to the white dwarf star had been accumulating material at a rate of about 1/1000 the mass of the Sun each year. This is the first known Type Ia supernova with a mostly helium outer layer, caused by mass accretion from a partner star.
Scientists noted, “This observation of radio waves from a helium-rich Type Ia supernova is expected to deepen our understanding of the explosion mechanism and conditions for a Type Ia supernova. Further plans include searching for radio emissions from other Type Ia supernovae to elucidate the evolution leading to the explosion.”
- Kool, EC, Johansson, J., Sollerman, J. et al. A radio-detected type Ia supernova with helium-rich circumstellar material. Nature 617, 477-482 (2023). DOI: 10.1038/s41586-023-05916-w