SN 2024igg: A Super-Chandrasekhar/03fg-like SN exhibiting C II-dominated spectra after explosion
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2026
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| author | Liu, Jialian Wang, Xiaofeng Chen, Liyang Filippenko, Alexei V. Brink, Thomas G. Zheng, WeiKang Pastorello, Andrea Ochner, Paolo Albanese, Irene Reguitti, Andrea Valerin, Giorgio Cai, Yongzhi Zhang, Jujia Li, Liping Wang, Zhenyu Liu, Liangduan Zhang, Yuhao |
| author_facet | Liu, Jialian Wang, Xiaofeng Chen, Liyang Filippenko, Alexei V. Brink, Thomas G. Zheng, WeiKang Pastorello, Andrea Ochner, Paolo Albanese, Irene Reguitti, Andrea Valerin, Giorgio Cai, Yongzhi Zhang, Jujia Li, Liping Wang, Zhenyu Liu, Liangduan Zhang, Yuhao |
| contents | We present and analyze photometric and spectroscopic observations of the Type Ia supernova (SN Ia) 2024igg, another ``super-Chandrasekhar'' (or 03fg-like) SN whose strong C II $\lambda6580$ feature was initially misidentified as H$α$, thereby constraining its progenitor system, explosion parameters, and physical scenario. SN 2024igg shows many characteristics in common with other 03fg-like objects, such as high ultraviolet flux, slowly declining light curves ($Δm_{15}(B)=0.90\pm0.08$ mag), low expansion velocities, along with strong and persistent C II absorption. Meanwhile, this SN exhibits some remarkable properties within this subgroup, including a moderately low optical luminosity ($M_{\rm max}(B)=-18.99\pm0.15$ mag), a short rise time less than 18.5 days, and strong C II $\lambda6580$. The bolometric analysis yields a $^{56}$Ni mass of $M_{\rm Ni}=0.547\pm0.082$ $M_{\rm \odot}$ and an ejecta mass of $1.54^{+0.22}_{-0.19}$ $M_{\rm \odot}$, marginally exceeding the Chandrasekhar mass. Our TARDIS result indicates that most of the features in the earliest spectrum could be attributed to C II, which is consistent with a model where a supernova explodes within a carbon-rich circumstellar medium (CSM). The CSM interaction would produce a density peak in the ejecta, offering a natural explanation for the slowly evolving line velocities near $-$8000 km s$^{-1}$. The CSM may stem from the debris of a secondary white dwarf in a white-dwarf merger or the envelope of an asymptotic giant branch star. Combined with the unshifted forbidden lines in the spectrum taken at $t\approx\ +$135 days, we suggest that SN 2024igg comes from a symmetric explosion on a secular timescale after the merger. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2602_03427 |
| institution | arXiv |
| publishDate | 2026 |
| record_format | arxiv |
| spellingShingle | SN 2024igg: A Super-Chandrasekhar/03fg-like SN exhibiting C II-dominated spectra after explosion Liu, Jialian Wang, Xiaofeng Chen, Liyang Filippenko, Alexei V. Brink, Thomas G. Zheng, WeiKang Pastorello, Andrea Ochner, Paolo Albanese, Irene Reguitti, Andrea Valerin, Giorgio Cai, Yongzhi Zhang, Jujia Li, Liping Wang, Zhenyu Liu, Liangduan Zhang, Yuhao High Energy Astrophysical Phenomena We present and analyze photometric and spectroscopic observations of the Type Ia supernova (SN Ia) 2024igg, another ``super-Chandrasekhar'' (or 03fg-like) SN whose strong C II $\lambda6580$ feature was initially misidentified as H$α$, thereby constraining its progenitor system, explosion parameters, and physical scenario. SN 2024igg shows many characteristics in common with other 03fg-like objects, such as high ultraviolet flux, slowly declining light curves ($Δm_{15}(B)=0.90\pm0.08$ mag), low expansion velocities, along with strong and persistent C II absorption. Meanwhile, this SN exhibits some remarkable properties within this subgroup, including a moderately low optical luminosity ($M_{\rm max}(B)=-18.99\pm0.15$ mag), a short rise time less than 18.5 days, and strong C II $\lambda6580$. The bolometric analysis yields a $^{56}$Ni mass of $M_{\rm Ni}=0.547\pm0.082$ $M_{\rm \odot}$ and an ejecta mass of $1.54^{+0.22}_{-0.19}$ $M_{\rm \odot}$, marginally exceeding the Chandrasekhar mass. Our TARDIS result indicates that most of the features in the earliest spectrum could be attributed to C II, which is consistent with a model where a supernova explodes within a carbon-rich circumstellar medium (CSM). The CSM interaction would produce a density peak in the ejecta, offering a natural explanation for the slowly evolving line velocities near $-$8000 km s$^{-1}$. The CSM may stem from the debris of a secondary white dwarf in a white-dwarf merger or the envelope of an asymptotic giant branch star. Combined with the unshifted forbidden lines in the spectrum taken at $t\approx\ +$135 days, we suggest that SN 2024igg comes from a symmetric explosion on a secular timescale after the merger. |
| title | SN 2024igg: A Super-Chandrasekhar/03fg-like SN exhibiting C II-dominated spectra after explosion |
| topic | High Energy Astrophysical Phenomena |
| url | https://arxiv.org/abs/2602.03427 |