2021MNRAS.502.3829T

SN 2017ein is a narrow-lined Type Ic SN that was found to share a location with a point-like source in the face on spiral galaxy NGC 3938 in pre-supernova images, making SN 2017ein the first credible detection of a Type Ic progenitor. Results in the literature suggest that this point-like source is likely a massive progenitor of 60-80 M_☉, depending on if the source is a binary, a single star, or a compact cluster. Using new photometric and spectral data collected for 200 d, including several nebular spectra, we generate a consistent model covering the photospheric and nebular phase using a Monte Carlo radiation transport code. Photospheric phase modelling finds an ejected mass 1.2-2.0 M_☉ with an E_k of ∼(0.9 ± 0.2) x 10⁵¹ erg, with approximately 1 M_☉ of material below 5000 km s^–1 found from the nebular spectra. Both photospheric and nebular phase modelling suggests a ⁵⁶Ni mass of 0.08-0.1 M_☉. Modelling the [O I] emission feature in the nebular spectra suggests that the innermost ejecta are asymmetric. The modelling results favour a low-mass progenitor of 16-20 M_☉, which is in disagreement with the pre-supernova derived high-mass progenitor. This contradiction is likely due to the pre-supernova source not representing the actual progenitor.