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Description
Type Ic supernovae (SNe) are explosive deaths of massive stars that have lost their
hydrogen and helium layers before explosion. In almost all cases this H-rich material is not found near SNe Ic, presumably swept away by the progenitor's strong stellar winds. SN 2017dio is a type Ic SN interacting with hydrogen-rich circumstellar material (CSM), challenging the models of massive-star evolution in how to create an SN of this kind.
We present late-time spectroscopy and photometry of the Type Ic SN 2017dio, whose light
curve and spectral evolution are dominated by strong ejecta-CSM interaction. Modeling the
optical emission and an infrared (IR) echo reveals two distinct CSM components: an inner CSM produced by a mass-loss rate of $\sim 0.2 ~\mathrm{yr}^{-1}$ over the 4–65 years before explosion, and a more distant dusty CSM at $\sim 0.1$ pc, corresponding to a mass-loss phase approximately 1000 years before explosion. The dust evaporation radius ($\sim$ 0.017 pc) lies interior to the observed IR-emitting region, implying a low-density gap between the inner and outer CSM.
The combination of a helium-stripped progenitor and hydrogen-rich CSM, together with the timing of the final mass-loss event, suggests that the CSM was created by a binary companion rather than the progenitor itself.