Carbon burning cannot explain puffy hypervelocity white dwarfs
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| Format: | Preprint |
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2025
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| _version_ | 1866916954180157440 |
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| author | Yamaguchi, Natsuko El-Badry, Kareem Wong, Tin Long Sunny Shen, Ken J. |
| author_facet | Yamaguchi, Natsuko El-Badry, Kareem Wong, Tin Long Sunny Shen, Ken J. |
| contents | Several hypervelocity white dwarfs (HVWDs) with space velocities of $\gtrsim 1000\,\mathrm{kms}^{-1}$ have recently been discovered. One possible origin of these stars is the dynamically-driven double-degenerate double-detonation (D6) scenario, in which an accreting sub-Chandrasekhar mass carbon-oxygen (CO) WD detonates as a SN Ia. In this scenario, the less massive WD may survive its companion's detonation and be ejected as a HVWD. Most of the observed HVWDs are hotter and puffier than normal WDs, perhaps due to their recent proximity to a SN. In this work, we test whether these properties can be explained by long-lived stable carbon (C) burning in the interiors of CO WD donors triggered by a SN shock. We model the long-term evolution of CO WDs following rapid energy injection using 1D models. We find that stable C burning can be ignited in CO WDs with masses of $0.95 - 1.10\,M_{\odot}$ if SN energy penetrates sufficiently deeply. The resulting born-again stars settle on the C-burning main sequence while they convert their interiors from C and O to Ne and Mg, where they have temperatures and radii similar to some of the observed HVWDs. However, the timescale over which C-burning WDs remain inflated is $\lesssim 10^5\,$yr, which is at least an order of magnitude shorter than the kinematic ages of observed hot HVWDs. We conclude that observed HVWDs are unlikely to be inflated by C burning. The stellar evolution of observed HVWDs remains an open problem. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2507_15952 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Carbon burning cannot explain puffy hypervelocity white dwarfs Yamaguchi, Natsuko El-Badry, Kareem Wong, Tin Long Sunny Shen, Ken J. Solar and Stellar Astrophysics High Energy Astrophysical Phenomena Several hypervelocity white dwarfs (HVWDs) with space velocities of $\gtrsim 1000\,\mathrm{kms}^{-1}$ have recently been discovered. One possible origin of these stars is the dynamically-driven double-degenerate double-detonation (D6) scenario, in which an accreting sub-Chandrasekhar mass carbon-oxygen (CO) WD detonates as a SN Ia. In this scenario, the less massive WD may survive its companion's detonation and be ejected as a HVWD. Most of the observed HVWDs are hotter and puffier than normal WDs, perhaps due to their recent proximity to a SN. In this work, we test whether these properties can be explained by long-lived stable carbon (C) burning in the interiors of CO WD donors triggered by a SN shock. We model the long-term evolution of CO WDs following rapid energy injection using 1D models. We find that stable C burning can be ignited in CO WDs with masses of $0.95 - 1.10\,M_{\odot}$ if SN energy penetrates sufficiently deeply. The resulting born-again stars settle on the C-burning main sequence while they convert their interiors from C and O to Ne and Mg, where they have temperatures and radii similar to some of the observed HVWDs. However, the timescale over which C-burning WDs remain inflated is $\lesssim 10^5\,$yr, which is at least an order of magnitude shorter than the kinematic ages of observed hot HVWDs. We conclude that observed HVWDs are unlikely to be inflated by C burning. The stellar evolution of observed HVWDs remains an open problem. |
| title | Carbon burning cannot explain puffy hypervelocity white dwarfs |
| topic | Solar and Stellar Astrophysics High Energy Astrophysical Phenomena |
| url | https://arxiv.org/abs/2507.15952 |