# Radii and Mass-loss Rates of Type IIb Supernova Progenitors

## TL;DR

This paper models binary star evolution to explain the observed correlation between supernova progenitor radii and mass-loss rates, suggesting non-conservative mass transfer as a key factor and linking some Type IIb supernovae to dense circumstellar matter and luminous Type IIn supernovae.

## Contribution

It introduces binary evolution models that explain the progenitor properties of Type IIb supernovae without fine tuning, highlighting the role of non-conservative mass transfer.

## Key findings

- Progenitor radius correlates with mass-loss rate due to binary interactions.
- Binary non-conservative mass transfer can produce dense circumstellar matter around supernova progenitors.
- Approximately 4% of Type IIn supernovae may originate from binary systems with high mass loss.

## Abstract

Several Type IIb supernovae (SNe IIb) have been extensively studied, both in terms of the progenitor radius and the mass-loss rate in the final centuries before the explosion. While the sample is still limited, evidence has been accumulating that the final mass-loss rate tends to be larger for a more extended progenitor, with the difference exceeding an order of magnitude between the more and less extended progenitors. The high mass-loss rates inferred for the more extended progenitors are not readily explained by a prescription commonly used for a single stellar wind. In this paper, we calculate a grid of binary evolution models. We show that the observational relation in the progenitor radii and mass-loss rates may be a consequence of non-conservative mass transfer in the final phase of progenitor evolution without fine tuning. Further, we find a possible link between SNe IIb and SNe IIn. The binary scenario for SNe IIb inevitably leads to a population of SN progenitors surrounded by dense circumstellar matter (CSM) due to extensive mass loss ($\dot{M} \gtrsim 10^{-4} M_{\odot} \mathrm{yr}^{-1}$) in the binary origin. About 4% of all observed SNe IIn are predicted to have dense CSM, produced by binary non-conservative mass transfer, whose observed characteristics are distinguishable from SNe IIn from other scenarios. Indeed, such SNe may be observationally dominated by systems experiencing huge mass loss in the final $10^3$ yr, leading to luminous SNe IIn or initially bright SNe IIP or IIL with characteristics of SNe IIn in their early spectra.