SN 2017dio: a type-Ic supernova exploding in a hydrogen-rich circumstellar medium

TL;DR

SN 2017dio is a rare type-Ic supernova interacting with a hydrogen-rich circumstellar medium, providing new insights into progenitor mass loss and explosion mechanisms.

Contribution

This paper presents the first confirmed case of a type-Ic supernova with hydrogen-rich CSM, using spectral analysis and light curve data.

Findings

Confirmed SN 2017dio as a type-Ic supernova with hydrogen-rich CSM.

Estimated progenitor mass loss rate of about 0.02 solar masses per year.

The CSM was likely shaped by eruptions or binary stripping, not steady winds.

Abstract

SN 2017dio shows both spectral characteristics of a type-Ic supernova (SN) and signs of a hydrogen-rich circumstellar medium (CSM). Prominent, narrow emission lines of H and He are superposed on the continuum. Subsequent evolution revealed that the SN ejecta are interacting with the CSM. The initial SN Ic identification was confirmed by removing the CSM interaction component from the spectrum and comparing with known SNe Ic, and reversely, adding a CSM interaction component to the spectra of known SNe Ic and comparing them to SN 2017dio. Excellent agreement was obtained with both procedures, reinforcing the SN Ic classification. The light curve constrains the pre-interaction SN Ic peak absolute magnitude to be around $M_g = -17.6$ mag. No evidence of significant extinction is found, ruling out a brighter luminosity required by a SN Ia classification. These pieces of evidence support the view that SN 2017dio is a SN Ic, and therefore the first firm case of a SN Ic with signatures of hydrogen-rich CSM in the early spectrum. The CSM is unlikely to have been shaped by steady-state stellar winds. The mass loss of the progenitor star must have been intense, $\dot{M} \sim 0.02$ $(\epsilon_{H\alpha}/0.01)^{-1}$ $(v_\textrm{wind}/500$ km s$^{-1}$) $(v_\textrm{shock}/10 000$ km s$^{-1})^{-3}$ $M_\odot$~yr$^{-1}$, peaking at a few decades before the SN. Such a high mass loss rate might have been experienced by the progenitor through eruptions or binary stripping.