BROAD-BAND X-RAY OBSERVATIONS OF THE ORION REGION WITH ASCA

Broad-band X-ray images and spectra of the Orion Nebula region were ob tained with the X-ray satellite ASCA. Fifty two point-like sources wer e resolved, including the Orion Trapezium. A large fraction of the opt ical counterparts of the ASCA sources were classified as G-M type star s. Spectral model fits and count ratios (flux ratio between soft and b road bands) revealed that most of the point sources exhibit a high-tem perature plasma of similar to 2-5 keV. Model fits of the X-ray spectra from extended regions around the Orion Nebula (M42), the reflection n ebula NGC 1977, and the sky between these nebulae required at least tw o-temperature components of typically 0.7-1 keV and 3-5 keV. From sele cted high-flux sources, we also found that the model of a 2-temperatur e thin thermal plasma is more likely than that of a single-temperature . X-ray light curves from these sources were time variable, but showed no large flares. We thus suggest that the hard X-rays are generated e ven in relatively quiescent states.