Weakened magnetic braking as the origin of anomalously rapid rotation in old field stars
| Autor: | Jennifer L. van Saders, Rafael A. García, Travis S. Metcalfe, T. Ceillier, Marc H. Pinsonneault, Victor Silva Aguirre, Savita Mathur, Guy R. Davies |
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| Rok vydání: | 2016 |
| Předmět: |
Physics
Rotation period Multidisciplinary 010308 nuclear & particles physics K-type main-sequence star Stellar collision Astronomy FOS: Physical sciences Astrophysics Astrophysics::Cosmology and Extragalactic Astrophysics 01 natural sciences Blue straggler T Tauri star Astrophysics - Solar and Stellar Astrophysics Stellar dynamics Stellar mass loss 0103 physical sciences Astrophysics::Solar and Stellar Astrophysics Gyrochronology Astrophysics::Earth and Planetary Astrophysics 010303 astronomy & astrophysics Astrophysics::Galaxy Astrophysics Solar and Stellar Astrophysics (astro-ph.SR) |
| Zdroj: | van Saders, J L, Ceillier, T, Metcalfe, T S, Silva Aguirre, V, Pinsonneault, M H, García, R A, Mathur, S & Davies, G R 2016, ' Weakened magnetic braking as the origin of anomalously rapid rotation in old field stars ', Nature, vol. 529, no. 7585, pp. 181-184 . https://doi.org/10.1038/nature16168 |
| DOI: | 10.48550/arxiv.1601.02631 |
| Popis: | A knowledge of stellar ages is crucial for our understanding of many astrophysical phenomena, and yet ages can be difficult to determine. As they become older, stars lose mass and angular momentum, resulting in an observed slowdown in surface rotation. The technique of 'gyrochronology' uses the rotation period of a star to calculate its age. However, stars of known age must be used for calibration, and, until recently, the approach was untested for old stars (older than 1 gigayear, Gyr). Rotation periods are now known for stars in an open cluster of intermediate age (NGC 6819; 2.5 Gyr old), and for old field stars whose ages have been determined with asteroseismology. The data for the cluster agree with previous period-age relations, but these relations fail to describe the asteroseismic sample. Here we report stellar evolutionary modelling, and confirm the presence of unexpectedly rapid rotation in stars that are more evolved than the Sun. We demonstrate that models that incorporate dramatically weakened magnetic braking for old stars can---unlike existing models---reproduce both the asteroseismic and the cluster data. Our findings might suggest a fundamental change in the nature of ageing stellar dynamos, with the Sun being close to the critical transition to much weaker magnetized winds. This weakened braking limits the diagnostic power of gyrochronology for those stars that are more than halfway through their main-sequence lifetimes. Comment: 25 pages, 3 figures in main paper, 6 extended data figures, 1 table. Published in Nature, January 2016. Please see https://youtu.be/O6HzYgP5uyc for a video description of the result |
| Databáze: | OpenAIRE |
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