X-rays, Rotation, and Magnetic Dynamos in the Orion Nebula Cluster
Eric Feigelson
Institute: Penn State University
Contact Email: edf@astro.psu.edu
Abstract:
Two 12-hour observations of the Orion Nebula Cluster obtained with the
Chandra X-ray Observatory and its ACIS detector provide detailed X-ray
properties for 1100 pre-main sequence stars with masses between 0.05 and
50 solar masses. Most of these stars have well-characterized optical/IR
properties, and almost 300 have photometrically measured rotational periods.
This provides a unique
dataset for the study of the relationship between X-ray emission, an
important tracer of magnetic activity, and rotational period or
Rossby number. The results indicate that the strong activity/rotation
correlation well-established in main sequence stars is not clearly
present in pre-main sequence stars. The phenomenon cannot be entirely
attributed to magnetic saturation of the surface, as some slowly
rotating stars are extremely magnetically active. This finding implies
that the standard alpha-omega dynamo is likely not responsible for
pre-main sequence magnetic activity. The activity might be attributed to a
more efficient turbulent dynamo process, or to a type of
reconnecting magnetic fields that are not present in main sequence stars
(e.g. star-disk or disk-disk field lines).
No manuscript was submitted to these Proceedings.
This work is published in
X-Ray-emitting Young Stars in the Orion Nebula by Feigelson, Eric D.;
Broos, Patrick; Gaffney, James A., III; Garmire, Gordon; Hillenbrand,
Lynne A.; Pravdo, Steven H.; Townsley, Leisa; Tsuboi, Yohko
2002, ApJ, 574, 258.
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Proceedings of 12th Cambridge Workshop on Cool Stars, Stellar Systems,
& The Sun,
© 2003 University of Colorado.