Cool Stars 14 - Submitted Abstract # 170
This version created on 05 October 2006

The Magnetic Field of the Class I Protostar WL 17


Christopher Johns-Krull, Rice University
Thomas Greene, NASA AMES
Greg Doppmann, Gemini Observatory
Kevin Covey, CfA/University of Washington

Strong stellar magnetic fields are believed to truncate the inner
accretion disks around young stars, redirecting the accreting material
to the high latitude regions of the stellar surface.  In the past few
years, observations of strong stellar fields on Classical T Tauri
stars [class II young stellar objects (YSOs)] with field strengths in
general agreement with the predictions of magnetopsheric accretion
theory have bolstered this picture.  Currently, nothing is known about
the magnetic field properties of younger, more embedded class I YSOs.
It is during this protostellar evolutionary phase that stars accrete
most of their final mass, but the physics governing this process
remains poorly understood.  Here, we use high resolution near infrared
spectra obtained with NIRSPEC on Keck and with PHOENIX on Gemini South
to measure the magnetic field properties of the class I protostar WL
17.  We find clear signatures of a strong stellar magnetic field.
Initial analysis of this data suggests a surface average field
strength of ~3.6 kG on the surface of WL 17.  This is the highest mean
surface field detected to date on any YSO.  We present our field
measurements and discuss how they fit with the general model of
magnetospheric accretion in young stars.

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