Spin-down of Solar-mass Protostars in Magnetospheric Accretion Paradigm
Stellar spin is one of the fundamental quantities that characterize a star itself and its planetary system. Nevertheless, stellar spin-down mechanisms in protostellar and pre-main-sequence stellar phases have been a long-standing problem in star formation theory. To realize the spin-down, previous a...
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| Main Authors: | , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
IOP Publishing
2025-01-01
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| Series: | The Astrophysical Journal |
| Subjects: | |
| Online Access: | https://doi.org/10.3847/1538-4357/ada364 |
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| Summary: | Stellar spin is one of the fundamental quantities that characterize a star itself and its planetary system. Nevertheless, stellar spin-down mechanisms in protostellar and pre-main-sequence stellar phases have been a long-standing problem in star formation theory. To realize the spin-down, previous axisymmetric models based on the conventional magnetospheric paradigm have had to assume massive stellar winds or produce highly time-variable magnetospheric ejections. However, this picture has been challenged by both numerical simulations and observations. With a particular focus on the propeller regime for solar-mass stars, we propose a new picture of stellar spin-down based on our recent 3D magnetohydrodynamic simulation and stellar evolution calculation. We show that failed magnetospheric winds, unique to 3D models, significantly reduce the spin-up accretion torque, which make it easier for the star to spin-down. Additionally, the amplitude of time variability associated with magnetospheric ejections is reduced by 3D effects. Our simulation demonstrates that the star spins down by generating a conical disk wind, driven by a rotating stellar magnetosphere. Our theoretical estimates, inspired by the numerical model, suggest that the conical disk wind is likely to play a crucial role in extracting stellar angular momentum during the protostellar phase. As magnetospheric accretion is expected to occur in other accreting objects such as protogiant planets, this study will also contribute to the understanding of the angular momentum of such objects. |
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| ISSN: | 1538-4357 |