Abstract
We present a series of spectra from hot stars obtained with the high energy transmission grating spectrometer (HETGS) onboard the Chandra X-ray Observatory. Most of the selected stars are located at or near the centers of young star-forming regions, which include IC 1396, NGC 2362, and Orion. The median ages of these clusters range from 0.3 to 12 Myr. The X-ray properties of these young, hot stars are then compared to a highly resolved X-ray spectrum of the more evolved field star zeta Pup. Cluster stars with ages larger than 3 Myr show moderate temperatures and broad asymmetric lines. These properties are quite similar to what has been observed in zeta Pup and are consistent with X-rays produced by shock instabilities in a radiation-driven wind. Stars with ages significantly less than 1 Myr, as found in the Orion Trapezium, show completely different characteristics. Here most of the X-ray flux shows very high temperatures and the X-ray lines are narrow and unresolved. This strongly indicates that the X-ray properties are dominated by magnetic field effects.
