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Measuring T Tauri star magnetic fields

Published online by Cambridge University Press:  01 November 2008

Christopher M. Johns–Krull
Christopher M. Johns–Krull*
Affiliation:
Department of Physics and Astronomy, Rice University, Houston, TX 77005, USA email: [email protected]
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Abstract

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Stellar magnetic fields including a strong dipole component are believed to play a critical role in the early evolution of newly formed stars and their circumstellar accretion disks. It is currently believed that the stellar magnetic field truncates the accretion disk several stellar radii above the star. This action forces accreting material to flow along the field lines and accrete onto the star preferentially at high stellar latitudes. It is also thought that the stellar rotation rate becomes locked to the Keplerian velocity near the radius where the disk is truncated. This paper reviews recent efforts to measure the magnetic field properties of low mass pre-main sequence stars, focussing on how the observations compare with the theoretical expectations. A picture is emerging indicating that quite strong fields do indeed cover the majority of the surface on these stars; however, the dipole component of the field appears to be alarmingly small. The current measurements also suggest that given their strong magnetic fields, T Tauri stars are somewhat faint in X-rays relative to what is expected from simple main sequence star scaling laws.

Keywords

Accretion – accretion disks – stars: formation – stars: magnetic fields – stars: pre-main-sequence
Type
Contributed Papers
Information
Proceedings of the International Astronomical Union , Volume 4 , Symposium S259: Cosmic Magnetic Fields: From Planets, to Stars and Galaxies , November 2008 , pp. 345 - 356
Copyright
Copyright © International Astronomical Union 2009

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