Published November 15, 2018 | Version v1
Poster Open

The magnetic obliquity of accreting T Tauri stars

  • 1. IPAG

Description

Accretion of matter from a T Tauri star's circumstellar disk is regulated by its magnetic field. The angle between the magnetic and rotational axes, the magnetic obliquity, is a crucial aspect of magnetospheric accretion models. It has strong implications on the structure of accretion/ejection flows and the occurrence of inner disk warps. We derive here the magnetic obliquity of a sample of 11 T Tauri stars in Taurus by monitoring HeI radial velocity variations along these stars' rotational cycles. The HeI 5876A emission line is produced in the accretion shock located at the base of the magnetic funnel flow. Whenever there is a misalignment between the magnetic and rotational axes, this line's radial velocity shows variability modulated by the stellar rotation with an amplitude that is directly related to the star's vsini (projected rotational velocity) and the latitude of the accretion shock. We find that most of the magnetic obliquities in our sample are between 5 and 15 degrees, with a few cases reaching nearly 30 degrees. We also investigate how these obliquities associate with other accretion signatures in the stellar spectra and with the stars' photometric variability.

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