Feigelson, Eric

Contact Email: edf@astro.psu.edu
Institute: Penn State University
Research URL:http://www.astro.psu.edu/users/edf
Presenting Thesis: Yes
Subject Area: Star Clusters, Associations
Waveband: X-rays
Technique: Imaging (Direct)
Presentation: Oral Contribution: Monday
Title: X-rays, rotation and the magnetic dynamo in the Orion Nebula Cluster
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 $0.05 < M_\odot < 50$. 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).