Formation of circumstellar material during double-white-dwarf mergers and the early excess emissions in Type Ia supernovae

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Main Authors: Inoue, Yusuke, Maeda, Keiichi, Nagao, Takashi, Matsumoto, Tatsuya
Format: Preprint
Published: 2025
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author Inoue, Yusuke
Maeda, Keiichi
Nagao, Takashi
Matsumoto, Tatsuya
author_facet Inoue, Yusuke
Maeda, Keiichi
Nagao, Takashi
Matsumoto, Tatsuya
contents Early excess emission observed in Type Ia supernovae (SNe Ia) within $\sim1$ day of explosion provides a critical window into their progenitor systems. In the present study, we investigate formation of the circumstellar matter (CSM) in double white-dwarf (WD) mergers. We further study the interaction between the CSM and the SN ejecta. We first model the orbital evolution and super-Eddington mass transfer/ejection in the double WD systems. We then conduct hydrodynamical and light-curve (LC) simulations of the SN-CSM interaction, assuming a prompt SN Ia explosion in a context of the carbon-ignited violent merger (C-ignited VM). Our simulations show that at the moment of the merger, the binary system has the CSM distribution following $ρ_{\mathrm{CSM}}\simeq D(r/10^{14}\ \mathrm{cm})^{-3.5}\ (D\simeq 10^{-14}\text{--}10^{-13}\ \rm g\ cm^{-3})$. The simulated LCs reproduce the early flux excesses across optical to UV bands, as well as their color evolution, observed in the VM candidates, i.e., 03fg/02es-like SNe Ia. This supports that 03fg/02es-like objects originate from the VM explosions. We also discuss the case of the helium-ignited VM, which might be realized in some WD-WD mergers depending on the He content in the system. Focused here is the timing when the explosion is initiated, and we find that the explosion is initiated after the companion WD is, at least partially, tidally disrupted also in this case; we thus expect the formation of the CSM through the mass transfer phase also for the helium-ignited VM scenario.
format Preprint
id arxiv_https___arxiv_org_abs_2512_10014
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Formation of circumstellar material during double-white-dwarf mergers and the early excess emissions in Type Ia supernovae
Inoue, Yusuke
Maeda, Keiichi
Nagao, Takashi
Matsumoto, Tatsuya
High Energy Astrophysical Phenomena
Solar and Stellar Astrophysics
Early excess emission observed in Type Ia supernovae (SNe Ia) within $\sim1$ day of explosion provides a critical window into their progenitor systems. In the present study, we investigate formation of the circumstellar matter (CSM) in double white-dwarf (WD) mergers. We further study the interaction between the CSM and the SN ejecta. We first model the orbital evolution and super-Eddington mass transfer/ejection in the double WD systems. We then conduct hydrodynamical and light-curve (LC) simulations of the SN-CSM interaction, assuming a prompt SN Ia explosion in a context of the carbon-ignited violent merger (C-ignited VM). Our simulations show that at the moment of the merger, the binary system has the CSM distribution following $ρ_{\mathrm{CSM}}\simeq D(r/10^{14}\ \mathrm{cm})^{-3.5}\ (D\simeq 10^{-14}\text{--}10^{-13}\ \rm g\ cm^{-3})$. The simulated LCs reproduce the early flux excesses across optical to UV bands, as well as their color evolution, observed in the VM candidates, i.e., 03fg/02es-like SNe Ia. This supports that 03fg/02es-like objects originate from the VM explosions. We also discuss the case of the helium-ignited VM, which might be realized in some WD-WD mergers depending on the He content in the system. Focused here is the timing when the explosion is initiated, and we find that the explosion is initiated after the companion WD is, at least partially, tidally disrupted also in this case; we thus expect the formation of the CSM through the mass transfer phase also for the helium-ignited VM scenario.
title Formation of circumstellar material during double-white-dwarf mergers and the early excess emissions in Type Ia supernovae
topic High Energy Astrophysical Phenomena
Solar and Stellar Astrophysics
url https://arxiv.org/abs/2512.10014