Optical photometry of SN 2020aeuh

At early times, the evolution of SN2020aeuh resembles a slightly overluminous SN~Ia. Later, the interaction-dominated spectra develop the same pseudocontinuum seen in Type Ia-CSM PTF11kx and SN 2020eyj. However, the later-time spectra of SN2020aeuh lack hydrogen and helium narrow lines.

Instead, a few narrow lines could be attributed to carbon and oxygen. We fit the pseudobolometric light curve with a CSM-interaction model, yielding a CSM mass of 1-2M_{sun}_. We propose that SN2020aeuh was a Type Ia supernova that eventually interacted with a dense medium which was deficient in both hydrogen and helium.

Whereas previous SNe Ia-CSM constitute our best evidence for nondegenerate companion progenitors, the CSM around SN2020aeuh is more difficult to understand. We include a hydrodynamical simulation for a double-degenerate dynamical collision to showcase that such a progenitor scenario could produce significant amounts of hydrogen-poor CSM, although likely not as much as the inferred CSM mass around SN2020aeuh. It is clear that SN2020aeuh challenges current models for stellar evolution leading up to a SN Ia explosion.