Magnetic accretion onto young stars |
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| Authors: | Nancy S Brickhouse |
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| Institution: | (1) Centro de Astrofísica da Universidade do Porto, Rua das Estrelas, 4150-762 Porto, Portugal |
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| Abstract: | Young T Tauri stars exhibit strong solar-type magnetic activity, with extremely high temperature coronae and energetic flares.
In a few systems discovered with Chandra and XMM-Newton there is also evidence for X-ray emission produced by shocks associated
with magnetically channeled accretion. A recent 489 ksec Chandra HETG/ACIS-S observation of the classical T Tauri star TW
Hydrae has provided a wealth of spectroscopic diagnostics not available in lower signal-to-noise ratio observations. Using
line ratios for electron temperature, electron density, and column density we have found that the shock produced by the accelerating
material in the accretion stream behaves as predicted by standard theory. However, the properties of the post-shock plasma
differ substantially from the predictions of standard 1D shock models (Brickhouse et al. in Astrophys. J. 710:1835, 2010). The accretion process apparently heats the stellar atmosphere up to soft X-ray emitting temperatures, providing hot ions
to populate the magnetic corona, in loops, stellar wind, and/or jets. This gas is highly turbulent, as evidenced by non-thermal
line broadening. The observed properties of the accretion-fed corona should constrain theoretical models of an accretion-driven
dynamo. |
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