The HETGS Orion Legacy Project

Paola Testa (MIT Kavli Institute for Astrophysics and Space Research) , Norbert S. Schulz (MIT), David P. Huenemoerder (MIT), Claude R. Canizares (MIT), Joel Kastner (RIT)

The Orion Trapezium Cluster (OTC) at the heart of the Orion Nebula is one of the youngest and closest star forming regions to our Sun. Early Chandra observations resolved a large number of bright X-ray sources in the OTC from very young ( yr) stars of masses ranging from substellar to several tens of solar masses. Over the last eight Chandra observing cycles we scanned the OTC with the HETGS to obtain a homogenuous sample of high resolution X-ray spectra from very young stars which are assumed to be coeval in terms of their star formation history, possess similar chemical composition,and span a large mass range. So far we have accumulated over 85f the anticipated 590 ks of exposure. The set includes good quality spectra of several massive ZAMS stars, and we have identified three processes of X-ray production: standard line driven wind shocks, magnetic confinement of winds, and most recently binary induced magnetic reconnection. The most compelling cases for magnetic activity have been made for Ori E) and several PMS stars of K/M spectral type (e.g., MT Ori). The results include X-ray emissivities, temperatures, mission radii, plasma densities as well as short- and longterm variability of these sources. We compare the new results with properties previously found in some of these sources as well as other hot and cool stars.