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S.J. Wolk (Harvard-Smithsonian Center for Astrophysics), Chandra Orion Megasecond Project Collaboration
Arguably the most observed star forming region, the Orion nebula cluster (ONC) provides a large and relatively nearby sample of a pre-main-sequence stellar population that covers the initial mass function from brown dwarfs up to a 45 Msolar O star. Chandra instrument team leaders Murray and Garmire have devoted a substantial amount of GTO time to this region, both in cycle 1, and in this 850 ks GO collaboration with PI Feigelson. We summarize the current state of our understanding of the cluster. This includes:
- The X-ray detection of over 1000 stars, including brown dwarf candidates. X-ray emission originates from class I, II, and III protostars at the cores of the proplyds.
- The median X-ray luminosities of low-mass stars increase with increasing mass and decreasing stellar age.
- X-ray sources not associated with any optical/infrared counterpart trace a yet-to-be-discovered stellar population of deeply embedded, relatively massive ONC members.
- There is a high degree a variability in all types of stars.
- X-rays from high mass stars do not conform to existing models.
- There is no detection of any diffuse emission.
There is also a lack of consensus on several points:
- Whether or not X-ray luminosities are near the ``saturation'' level.
- The dependence of X-ray luminosity on the presence of a disk.
- Whether or not a relationship exists between X-ray luminosity and rotation.
We will also present a first look at the nearly megasecond worth of data taken in January 2003 and discuss our approach to analysis of this mammoth data set.
We acknowledge the CXC and HRC contracts (NAS8-39073 and NAS8-38248) for partial support of the work at SAO.
Bulletin of the American Astronomical Society,
© 2003. The American Astronomical Soceity.