Varying core-envelope coupling efficiency identified from stellar rotation--activity relation
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arXiv
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| Main Authors: | , , , , , , , |
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| Format: | Preprint |
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2025
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| _version_ | 1866915815151894528 |
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| author | Han, Henggeng Wang, Song Yang, Huiqin Li, Xue Zheng, Chuanjie Li, Xiangyu Wang, Cunshi Liu, Jifeng |
| author_facet | Han, Henggeng Wang, Song Yang, Huiqin Li, Xue Zheng, Chuanjie Li, Xiangyu Wang, Cunshi Liu, Jifeng |
| contents | Core-envelope coupling provides a reasonable explanation of the spin-down stalling of stars in open clusters, which was not predicted by classical gyrochronology. However, it remains an open question whether the coupling efficiency is constant or variable. M dwarfs, possessing thicker convective envelopes and thus longer coupling timescales than other late-type stars, are ideal objects for this investigation. In this work, based on the $R_{\rm{HK}}^{'}$ measurements from LAMOST and DESI spectra, we construct new rotation--activity relations for M dwarfs. Unlike the traditional picture, we suggest that the new relation consists of three distinct regimes of fast, intermediate, and slow rotation, closely matching the three sequences of gyrochronology, namely the ``Convective'' sequence, ``Gap'', and ``Interface'' sequence. Our study reveals, for the first time, a variable activity decay rate in the intermediate-rotation regime (i.e., the ``Gap'' region). This implies a varying core-envelope coupling efficiency, peaking towards the end of this region. It also coincides with the well-known stage of stalled stellar spin-down. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2512_11376 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Varying core-envelope coupling efficiency identified from stellar rotation--activity relation Han, Henggeng Wang, Song Yang, Huiqin Li, Xue Zheng, Chuanjie Li, Xiangyu Wang, Cunshi Liu, Jifeng Solar and Stellar Astrophysics Core-envelope coupling provides a reasonable explanation of the spin-down stalling of stars in open clusters, which was not predicted by classical gyrochronology. However, it remains an open question whether the coupling efficiency is constant or variable. M dwarfs, possessing thicker convective envelopes and thus longer coupling timescales than other late-type stars, are ideal objects for this investigation. In this work, based on the $R_{\rm{HK}}^{'}$ measurements from LAMOST and DESI spectra, we construct new rotation--activity relations for M dwarfs. Unlike the traditional picture, we suggest that the new relation consists of three distinct regimes of fast, intermediate, and slow rotation, closely matching the three sequences of gyrochronology, namely the ``Convective'' sequence, ``Gap'', and ``Interface'' sequence. Our study reveals, for the first time, a variable activity decay rate in the intermediate-rotation regime (i.e., the ``Gap'' region). This implies a varying core-envelope coupling efficiency, peaking towards the end of this region. It also coincides with the well-known stage of stalled stellar spin-down. |
| title | Varying core-envelope coupling efficiency identified from stellar rotation--activity relation |
| topic | Solar and Stellar Astrophysics |
| url | https://arxiv.org/abs/2512.11376 |