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SN Ia-CSM 2020aeuh: Massive binary C/O WD merger?

N. N. Chugai

TL;DR

This work investigates the origin of the circumstellar shell around the unusual SN Ia–CSM 2020aeuh by modeling CS interaction in a thin-shell framework and constraining key parameters from observations. The analysis yields a CS shell mass of $M_{cs}=0.04-0.2\,M_\\odot$, a shell radius of $R_{cs}\\approx2\times10^{16}$ cm, and a synthesized $M_{Ni}\\≈1\,M_\\odot$, with the CS expansion velocity limited to $u\\lesssim200$ km s$^{-1}$ and a delay between merger and explosion of $t_{del}\\gtrsim30$ yr. The results support a scenario where a merger of two massive C/O WDs ejects roughly $0.1\,M_\\odot$ and later explodes as SN 2020aeuh, providing a plausible link between WD mergers, CS shell formation, and overluminous SN Ia phenomenology. This places important constraints on WD merger outcomes and the timescales between merger and explosion, and suggests that substantial CS material can be present with modest outflow masses in such systems.

Abstract

I explore the origin of the circumstellar (CS) shell of the unusual SN Ia 2020aeuh based on the light curve model abd observational constraints. I estimate the $^{56}$Ni mass ($1.1 M\odot$), CS shell mass ($0.04-0.2 M\odot$), radius ($2\times10^{16}$ cm), and expansion velocity $\lesssim 200$ km/s. Large $^{56}$Ni mass and properties of the CS shell are consistent with the scenario of massive binary white dwarf merger that has been accompanied with the ejection of $\sim 0.1 M\odot$ of matter. It is argued that SN~2020aeuh exploded not earlier than 30 yr after the merger.

SN Ia-CSM 2020aeuh: Massive binary C/O WD merger?

TL;DR

This work investigates the origin of the circumstellar shell around the unusual SN Ia–CSM 2020aeuh by modeling CS interaction in a thin-shell framework and constraining key parameters from observations. The analysis yields a CS shell mass of , a shell radius of cm, and a synthesized , with the CS expansion velocity limited to km s and a delay between merger and explosion of yr. The results support a scenario where a merger of two massive C/O WDs ejects roughly and later explodes as SN 2020aeuh, providing a plausible link between WD mergers, CS shell formation, and overluminous SN Ia phenomenology. This places important constraints on WD merger outcomes and the timescales between merger and explosion, and suggests that substantial CS material can be present with modest outflow masses in such systems.

Abstract

I explore the origin of the circumstellar (CS) shell of the unusual SN Ia 2020aeuh based on the light curve model abd observational constraints. I estimate the Ni mass (), CS shell mass (), radius ( cm), and expansion velocity km/s. Large Ni mass and properties of the CS shell are consistent with the scenario of massive binary white dwarf merger that has been accompanied with the ejection of of matter. It is argued that SN~2020aeuh exploded not earlier than 30 yr after the merger.
Paper Structure (7 sections, 2 figures, 1 table)

This paper contains 7 sections, 2 figures, 1 table.

Table of Contents

  1. Introduction
  2. Preliminaries
  3. Mass of CS matter
  4. Discussion
  5. Conclusion
  6. Acknowledgements
  7. References

Figures (2)

  • Figure 1: Theoretical profile of a line emitted by the CS shell with the spherical velocity distribution, but non-spherical density distribution of equatorial type with the emissivity depending on the polar angle $\theta$ as $\epsilon \propto (1 - |\cos{\theta}|)^3$ for different cosine of an inclination angle.
  • Figure 2: Left. Model bolometric light curve (red line) overplotted on observational data (Tsalapatas et al. 2025). Inset shows CSM density distrbution. Right. The CDS velocity ( blue) and the radius ( dotted); maximum velocity of unshcked ejecta is shown by red line. The CDS velocity is consistent with the CDS velocity value inferred from the Ca ii 3933 Å line on day +99 (circle).