Spectra of V1405 Cas at the Very Beginning Indicate a Low-mass ONeMg White Dwarf Progenitor
The lowest possible mass of ONeMg white dwarfs (WDs) has not been clarified despite its importance in the formation and evolution of WDs. We tackle this issue by studying the properties of V1405 Cas (Nova Cassiopeiae 2021), which is an outlier given a combination of its very slow light-curve evoluti...
| Main Authors: | , , , , , , , , , , , |
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| Format: | Article |
| Language: | English |
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IOP Publishing
2023-01-01
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| Series: | The Astrophysical Journal |
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| Online Access: | https://doi.org/10.3847/1538-4357/ad0133 |
| _version_ | 1797539495448412160 |
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| author | Kenta Taguchi Keiichi Maeda Hiroyuki Maehara Akito Tajitsu Masayuki Yamanaka Akira Arai Keisuke Isogai Masaaki Shibata Yusuke Tampo Naoto Kojiguchi Daisaku Nogami Taichi Kato |
| author_facet | Kenta Taguchi Keiichi Maeda Hiroyuki Maehara Akito Tajitsu Masayuki Yamanaka Akira Arai Keisuke Isogai Masaaki Shibata Yusuke Tampo Naoto Kojiguchi Daisaku Nogami Taichi Kato |
| author_sort | Kenta Taguchi |
| collection | DOAJ |
| description | The lowest possible mass of ONeMg white dwarfs (WDs) has not been clarified despite its importance in the formation and evolution of WDs. We tackle this issue by studying the properties of V1405 Cas (Nova Cassiopeiae 2021), which is an outlier given a combination of its very slow light-curve evolution and the recently reported neon-nova identification. We report its rapid spectral evolution in the initial phase, covering 9.88, 23.77, 33.94, 53.53, 71.79, and 81.90 hr after the discovery. The first spectrum is characterized by lines from highly ionized species, most noticeably He ii and N iii . These lines are quickly replaced by lower-ionization lines, e.g., N ii , Si ii , and O i . In addition, Al ii (6237 Å) starts emerging as an emission line at the second epoch. We perform emission-line strength diagnostics, showing that the density and temperature quickly decrease toward later epochs. This behavior, together with the decreasing velocity seen in H α , H β , and He i , indicates that the initial nova dynamics is reasonably well described by an expanding fireball on top of an expanding photosphere. Interestingly, the strengths of the N iii and Al ii indicate large enhancement in abundance, pointing to a ONeMg WD progenitor as is consistent with its neon-nova classification. Given its low-mass nature inferred by the slow light-curve evolution and relatively narrow emission lines, it provides a challenge to the stellar evolution theory that predicts the lower limit of the ONeMg WD mass being ∼1.1 M _⊙ . |
| first_indexed | 2024-03-10T12:45:48Z |
| format | Article |
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| institution | Directory Open Access Journal |
| issn | 1538-4357 |
| language | English |
| last_indexed | 2024-03-10T12:45:48Z |
| publishDate | 2023-01-01 |
| publisher | IOP Publishing |
| record_format | Article |
| series | The Astrophysical Journal |
| spelling | doaj.art-b7b7fa0f906d43d28c949547db897fa82023-11-21T13:29:16ZengIOP PublishingThe Astrophysical Journal1538-43572023-01-01958215610.3847/1538-4357/ad0133Spectra of V1405 Cas at the Very Beginning Indicate a Low-mass ONeMg White Dwarf ProgenitorKenta Taguchi0https://orcid.org/0000-0002-8482-8993Keiichi Maeda1https://orcid.org/0000-0003-2611-7269Hiroyuki Maehara2https://orcid.org/0000-0003-0332-0811Akito Tajitsu3https://orcid.org/0000-0001-8813-9338Masayuki Yamanaka4https://orcid.org/0000-0001-9456-3709Akira Arai5https://orcid.org/0000-0002-5756-067XKeisuke Isogai6https://orcid.org/0000-0002-6480-3799Masaaki Shibata7Yusuke Tampo8https://orcid.org/0000-0003-0196-3936Naoto Kojiguchi9Daisaku Nogami10https://orcid.org/0000-0001-9588-1872Taichi Kato11Department of Astronomy, Kyoto University , Kitashirakawa-Oiwake-cho, Sakyo-ku, Kyoto 606-8502, Japan ; kentagch@kusastro.kyoto-u.ac.jp, taguchi.kenta.34z@kyoto-u.jpDepartment of Astronomy, Kyoto University , Kitashirakawa-Oiwake-cho, Sakyo-ku, Kyoto 606-8502, Japan ; kentagch@kusastro.kyoto-u.ac.jp, taguchi.kenta.34z@kyoto-u.jpSubaru Telescope Okayama Branch Office, National Astronomical Observatory of Japan , 3037-5, Honjou, Kamogata, Asakuchi, Okayama 719-0232, JapanSubaru Telescope Okayama Branch Office, National Astronomical Observatory of Japan , 3037-5, Honjou, Kamogata, Asakuchi, Okayama 719-0232, JapanOkayama Observatory, Kyoto University , 3037-5 Honjo, Kamogata-cho, Asakuchi, Okayama 719-0232, Japan; Amanogawa Galaxy Astronomy Research Center (AGARC), Graduate School of Science and Engineering, Kagoshima University , Kagoshima 890-0065, JapanSubaru Telescope, National Astronomical Observatory of Japan , 650 North A’ohoku Place, Hilo, HI 96720, USAOkayama Observatory, Kyoto University , 3037-5 Honjo, Kamogata-cho, Asakuchi, Okayama 719-0232, Japan; Department of Multi-Disciplinary Sciences, Graduate School of Arts and Sciences, The University of Tokyo , 3-8-1 Komaba, Meguro, Tokyo 153-8902, JapanDepartment of Astronomy, Kyoto University , Kitashirakawa-Oiwake-cho, Sakyo-ku, Kyoto 606-8502, Japan ; kentagch@kusastro.kyoto-u.ac.jp, taguchi.kenta.34z@kyoto-u.jpDepartment of Astronomy, Kyoto University , Kitashirakawa-Oiwake-cho, Sakyo-ku, Kyoto 606-8502, Japan ; kentagch@kusastro.kyoto-u.ac.jp, taguchi.kenta.34z@kyoto-u.jpDepartment of Astronomy, Kyoto University , Kitashirakawa-Oiwake-cho, Sakyo-ku, Kyoto 606-8502, Japan ; kentagch@kusastro.kyoto-u.ac.jp, taguchi.kenta.34z@kyoto-u.jpDepartment of Astronomy, Kyoto University , Kitashirakawa-Oiwake-cho, Sakyo-ku, Kyoto 606-8502, Japan ; kentagch@kusastro.kyoto-u.ac.jp, taguchi.kenta.34z@kyoto-u.jpDepartment of Astronomy, Kyoto University , Kitashirakawa-Oiwake-cho, Sakyo-ku, Kyoto 606-8502, Japan ; kentagch@kusastro.kyoto-u.ac.jp, taguchi.kenta.34z@kyoto-u.jpThe lowest possible mass of ONeMg white dwarfs (WDs) has not been clarified despite its importance in the formation and evolution of WDs. We tackle this issue by studying the properties of V1405 Cas (Nova Cassiopeiae 2021), which is an outlier given a combination of its very slow light-curve evolution and the recently reported neon-nova identification. We report its rapid spectral evolution in the initial phase, covering 9.88, 23.77, 33.94, 53.53, 71.79, and 81.90 hr after the discovery. The first spectrum is characterized by lines from highly ionized species, most noticeably He ii and N iii . These lines are quickly replaced by lower-ionization lines, e.g., N ii , Si ii , and O i . In addition, Al ii (6237 Å) starts emerging as an emission line at the second epoch. We perform emission-line strength diagnostics, showing that the density and temperature quickly decrease toward later epochs. This behavior, together with the decreasing velocity seen in H α , H β , and He i , indicates that the initial nova dynamics is reasonably well described by an expanding fireball on top of an expanding photosphere. Interestingly, the strengths of the N iii and Al ii indicate large enhancement in abundance, pointing to a ONeMg WD progenitor as is consistent with its neon-nova classification. Given its low-mass nature inferred by the slow light-curve evolution and relatively narrow emission lines, it provides a challenge to the stellar evolution theory that predicts the lower limit of the ONeMg WD mass being ∼1.1 M _⊙ .https://doi.org/10.3847/1538-4357/ad0133NovaeClassical novaeSlow novaeCataclysmic variable starsNova-like variable starsSpectral line identification |
| spellingShingle | Kenta Taguchi Keiichi Maeda Hiroyuki Maehara Akito Tajitsu Masayuki Yamanaka Akira Arai Keisuke Isogai Masaaki Shibata Yusuke Tampo Naoto Kojiguchi Daisaku Nogami Taichi Kato Spectra of V1405 Cas at the Very Beginning Indicate a Low-mass ONeMg White Dwarf Progenitor The Astrophysical Journal Novae Classical novae Slow novae Cataclysmic variable stars Nova-like variable stars Spectral line identification |
| title | Spectra of V1405 Cas at the Very Beginning Indicate a Low-mass ONeMg White Dwarf Progenitor |
| title_full | Spectra of V1405 Cas at the Very Beginning Indicate a Low-mass ONeMg White Dwarf Progenitor |
| title_fullStr | Spectra of V1405 Cas at the Very Beginning Indicate a Low-mass ONeMg White Dwarf Progenitor |
| title_full_unstemmed | Spectra of V1405 Cas at the Very Beginning Indicate a Low-mass ONeMg White Dwarf Progenitor |
| title_short | Spectra of V1405 Cas at the Very Beginning Indicate a Low-mass ONeMg White Dwarf Progenitor |
| title_sort | spectra of v1405 cas at the very beginning indicate a low mass onemg white dwarf progenitor |
| topic | Novae Classical novae Slow novae Cataclysmic variable stars Nova-like variable stars Spectral line identification |
| url | https://doi.org/10.3847/1538-4357/ad0133 |
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