The final months of massive star evolution from the circumstellar environment around SN Ic 2020oi

Understand

We present the results of ALMA band 3 observations of a nearby type Ic supernova (SN) 2020oi.

• Under the standard assumptions on the SN-circumstellar medium (CSM) interaction and the synchrotron emission, the data indicate that the CSM structure deviates from a smooth distribution expected from the steady-state mass loss in the very vicinity of the SN (~10^{15} cm), which is then connected to the outer smooth distribution (~10^{16} cm).
• This structure is further confirmed through the light curve modeling of the whole radio data set as combined with data at lower frequency previously reported.
• Being an explosion of a bare carbon-oxygen (C+O) star having a fast wind, we can trace the mass-loss history of the progenitor of SN 2020oi in the final year.