Cool Stars 14 - Submitted Abstract # 245
This version created on 05 October 2006

How Hot is the Wind from TW Hydrae?


Gregory J. Herczeg,  Caltech
Christopher M. Johns-Krull,  Rice University

It has recently been suggested that the winds from Classical T Tauri
stars in general, and the wind from TW Hya in particular, reaches
temperatures of at least 300,000  K while maintaing a mass loss rate
of 10^-11 or larger.  If confirmed, this would place strong new
requirements on wind launching and heating models.  We therefore
re-examine spectra from the Space Telescope Imaging Spectrograph
aboard the Hubble Space Telescope and spectra from the Far Ultraviolet
Spectroscopic Explorer satellite in an effort to better constrain the
maximum temperature in the wind of TW Hya.  We find clear evidence for
a wind in the C II doublet at 1037 A and in the C II multiplet at 1335
A.  We find no wind absorption in the C IV 1550  A doublet observed at
the same time as the C II 1335 A line or in observations of O VI
observed simultaneously with the C II 1037 A line.  The presence or
absence of C III wind absorption is ambiguous.  The clear lack of a
wind in the C IV line argues that the wind from TW Hya does not reach
the 100,000  K characteristic formation temperature of this line.  We
therefore argue that the available evidence suggests that the wind
from TW Hya, and probably all classical T Tauri stars, reaches a
maximum temperature in the range of 10,000  - 30,000  K.

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