Magnetic Braking of Accreting T Tauri Stars: Effects of Mass Accretion Rate, Rotation, and Dipolar Field Strength

Ireland, Lewis G.; Zanni, C.; Pantolmos, G.

doi:10.3847/1538-4357/abc828

Cited by 28 publications

(51 citation statements)

References 58 publications

(93 reference statements)

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“…1 2 . However, the accretion disk is not in Keplerian rotation, as the MEs exchange angular momentum with the surface of the disk (see, e.g., Zanni & Ferreira 2013;Pantolmos et al 2020;Ireland et al 2021). Therefore, we…”

Section: Star-disk Interaction Torque: Accretion and Mementioning

confidence: 99%

Magnetic Braking of Accreting T Tauri Stars II: Torque Formulation Spanning Spin-up and Spin-down Regimes

Ireland

Zanni

2022

ApJ

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The magnetic interaction between a classical T Tauri star and its surrounding accretion disk is thought to influence its rotational evolution. We use 2.5D magnetohydrodynamic, axisymmetric simulations of star-disk interaction, computed via the PLUTO code, to calculate the net torque acting on these stars. We divide the net torque into three contributions: accretion (spin-up), stellar winds (spin-down), and magnetospheric ejections (MEs) (spin-up or down). In Paper I, we explored interaction regimes in which the stellar magnetosphere truncates the inner disk at a location spinning faster than the star, resulting in a strong net spin-up contribution from accretion and MEs (“steady accretion” regime). In this paper, we investigate interaction regimes in which the truncation radius gets closer to and even exceeds corotation, where it is possible for the disk material to gain angular momentum and be periodically ejected by the centrifugal barrier (“propeller” regime). This reduces the accretion torque, can change the sign of the ME torque, and can result in a net stellar spin-down configuration. These results suggest it is possible to have a net spin-down stellar torque even for truncation radii within the corotation radius (R t ≳ 0.7R co). We fit semi-analytic functions for the truncation radius, and the torque associated with star-disk interaction (i.e., the sum of accretion and ME torques) and stellar wind, allowing for the prediction of the net stellar torque for a parameter regime covering both net spin-up and spin-down configurations, as well as the possibility of investigating rotational evolution via 1D stellar evolution codes.

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Section: Star-disk Interaction Torque: Accretion and Mementioning

confidence: 99%

Magnetic Braking of Accreting T Tauri Stars II: Torque Formulation Spanning Spin-up and Spin-down Regimes

Ireland

Zanni

2022

ApJ

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“…The analytical value of the accretion torque can be determined by assuming Keplerian rotation, i.e., Ω(𝑅 t ) = Ω K (𝑅 t ), giving 𝐽 acc,K = 𝑀 acc (𝐺 𝑀 ★ 𝑅 t ) 1/2 . However, the accretion disk is not in Keplerian rotation, as the MEs exchange angular momentum with the surface of the disk (see, e.g., Zanni & Ferreira 2013;Pantolmos et al 2020;Ireland et al 2021). Therefore, we rewrite Equation ( 10) as…”

Section: Star-disk Interaction Torque: Accretion and Mementioning

confidence: 99%

Magnetic Braking of Accreting T Tauri Stars II: Torque Formulation Spanning Spin-Up and Spin-Down Regimes

Ireland,

Matt,

Zanni

2022

Preprint

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The magnetic interaction between a classical T Tauri star and its surrounding accretion disk is thought to influence its rotational evolution. We use 2.5D magnetohydrodynamic, axisymmetric simulations of star-disk interaction, computed via the PLUTO code, to calculate the net torque acting on these stars. We divide the net torque into three contributions: accretion (spin-up), stellar winds (spin-down), and magnetospheric ejections (MEs) (spin-up or down). In Paper I, we explored interaction regimes in which the stellar magnetosphere truncates the inner disk at a location spinning faster than the star, resulting in a strong net spin-up contribution from accretion and MEs ("steady accretion" regime). In this paper, we investigate interaction regimes in which the truncation radius gets closer to and even exceeds corotation, where it is possible for the disk material to gain angular momentum and be periodically ejected by the centrifugal barrier ("propeller" regime). This reduces the accretion torque, can change the sign of the ME torque, and can result in a net stellar spin-down configuration. These results suggest it is possible to have a net spin-down stellar torque even for truncation radii within the corotation radius (𝑅 t 0.7𝑅 co ). We fit semi-analytic functions for the truncation radius, and the torque associated with star-disk interaction (i.e., the sum of accretion and ME torques) and stellar wind, allowing for the prediction of the net stellar torque for a parameter regime covering both net spin-up and spin-down configurations, as well as the possibility of investigating rotational evolution via 1D stellar evolution codes.

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“…External photoevaporation of disks will also shorten the star-diskinteraction (SDI) phase. During this phase, the magnetic interaction between stars and their accretion disks leads to an exchange of mass and angular momentum between the two (e.g., Ghosh & Lamb 1979;Koenigl 1991;Ireland et al 2021). Stars lose the vast majority of their angular momentum during their first ∼10 Myr, and it is thought that the SDI is the primary driver of the stars' angular momentum evolution (Bodenheimer 1995;Mathieu 2004;Bouvier et al 2014).…”

Section: Introductionmentioning

confidence: 99%

“…Stars lose the vast majority of their angular momentum during their first ∼10 Myr, and it is thought that the SDI is the primary driver of the stars' angular momentum evolution (Bodenheimer 1995;Mathieu 2004;Bouvier et al 2014). Physical models for the magnetic SDI show that the net result of this interaction can either spin up or spin down the star, driving the star's rotation toward an equilibrium spin rate (Ghosh & Lamb 1979;Matt & Pudritz 2005;Zanni & Ferreira 2009, 2013Ireland et al 2021). In this theoretical equilibrium state, the rotation rate of the star is dictated by a balance of torques, which is determined by (NGC 6811).…”

Section: Introductionmentioning

confidence: 99%

The influence of the environment on the spin evolution of low-mass stars. I. External photoevaporation of circumstellar disks

Roquette,

Matt,

Winter

et al. 2021

Preprint

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Massive stars are strong sources of far-ultraviolet radiation that can be hostile to the evolution of protoplanetary disks, driving mass loss by external photoevaporation and shortening disk-dissipation timescales. Their effect may also reduce the timescale of angular momentum exchanges between the disk and host star during the early pre-main-sequence phase. To improve our understanding of the environmental influence on the rotational history of stars, we developed a model that considers the influence of the local far-ultraviolet radiation on the spin evolution of low mass stars. Our model includes an assumption of disk-locking, which fixes the rotation rate during the star-disk-interaction phase, with the duration of this phase parametrised as a function of the local far-ultraviolet radiation and stellar mass (in the range 0.1-1.3 M ). In this way, we demonstrate how the feedback from massive stars can significantly influence the spin evolution of stars and explain the mass-dependency observed in period-mass distributions of young regions like Upper Sco and NGC 2264. The high far-ultraviolet environments of high-mass stars can skew the period distribution of surrounding stars towards fast-rotation, explaining the excess of fast-rotating stars in the open cluster h Per. The proposed link between rotation and the pre-main-sequence environment opens new avenues for interpreting the rotational distributions of young stars. For example, we suggest that stellar rotation may be used as a tracer for the primordial ultraviolet irradiation for stars up to ∼1 Gyr, which offers a potential method to connect mature planetary systems to their birth environment.

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Magnetic Braking of Accreting T Tauri Stars: Effects of Mass Accretion Rate, Rotation, and Dipolar Field Strength

Cited by 28 publications

References 58 publications

Magnetic Braking of Accreting T Tauri Stars II: Torque Formulation Spanning Spin-up and Spin-down Regimes

Magnetic Braking of Accreting T Tauri Stars II: Torque Formulation Spanning Spin-up and Spin-down Regimes

Magnetic Braking of Accreting T Tauri Stars II: Torque Formulation Spanning Spin-Up and Spin-Down Regimes

The influence of the environment on the spin evolution of low-mass stars. I. External photoevaporation of circumstellar disks

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