Type Ia supernovae (SNe Ia) are thermonuclear explosions of degenerate white dwarf stars destabilized by mass accretion from a companion star. However, the nature of their progenitors still needs to be better understood. A way to discriminate 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 by a Type Ia supernova. This is the first time astronomers have observed radio waves emitted by a Type Ia supernova, offering critical clues to understand how white dwarfs explode.
The team performed detailed observations of a Type Ia supernova- SN 2020eyj- that exploded in 2020. This supernova was surrounded by circumstellar material consisting mainly of helium, as demonstrated by its spectral features, infrared emission. To their surprise, scientists could also detect radio waves from supernovas.
Based on the modeling, scientists conclude that the circumstellar material probably originates from a single-degenerate binary system in which a white dwarf accretes material from a helium donor star, an often proposed formation channel for SNe Ia.
It was discovered that the progenitor white dwarf star had been accreting material at a rate of around 1/1000 the mass of the Sun every year by comparing the observed radio wave strength with theoretical models. This is the first known Type Ia supernova with an outer layer predominantly made of helium caused by mass accretion from a partner star.
Scientists noted, “It is expected that this observation of radio waves from a helium-rich Type Ia supernova will deepen our understanding of the explosion mechanism and the conditions before a Type Ia supernova. Further plans include searching for radio emissions from other Type Ia supernovae to elucidate the evolution which leads to the explosion.”