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A thermonuclear supernova interacting with hydrogen- and helium-deficient circumstellar material: SN 2020aeuh as a SN Ia-CSM-C/O?
Journal article   Open access   Peer reviewed

A thermonuclear supernova interacting with hydrogen- and helium-deficient circumstellar material: SN 2020aeuh as a SN Ia-CSM-C/O?

K. Tsalapatas, J. Sollerman, R. Chiba, E. Kool, J. Johansson, S. Rosswog, S. Schulze, T. J. Moriya, I. Andreoni, T. G. Brink, …
Astronomy and astrophysics (Berlin), v 704, 135
05 Dec 2025
DOI: https://doi.org/10.1051/0004-6361/202556369
url
https://doi.org/10.1051/0004-6361/202556369View
Published, Version of Record (VoR) Open

Abstract

Astronomy & Astrophysics Science & Technology Physical Sciences
Identifying the progenitors of thermonuclear supernovae (Type Ia supernovae; SNe Ia) remains a key objective in contemporary astronomy. The rare sub-class of SNe Ia-CSM that interacts with circumstellar material (CSM) allows for studies of the progenitor's environment before explosion, and generally favours single-degenerate progenitor channels. The case of SN Ia-CSM PTF11kx clearly connected thermonuclear explosions with hydrogen-rich CSM-interacting events, and the more recent SN 2020eyj connected SNe Ia with helium-rich companion progenitors. Both of these objects displayed delayed CSM interaction which established their thermonuclear nature. Here we present a study of SN 2020aeuh, a Type Ia-CSM with delayed interaction. We analyse photometric and spectroscopic data that monitor the evolution of SN 2020aeuh and compare its properties with those of peculiar SNe Ia and core-collapse SNe. At early times, the evolution of SN 2020aeuh 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 SN 2020aeuh 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 - 2 M-circle dot. We propose that SN 2020aeuh was a Type Ia supernova that eventually interacted with a dense medium that was deficient in both hydrogen and helium. Whereas previous SNe Ia-CSM constitute our best evidence of non-degenerate companion progenitors, the CSM around SN 2020aeuh 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 SN 2020aeuh. It is clear that SN 2020aeuh challenges current models of stellar evolution leading up to a SN Ia explosion.

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