ChandraObservations of Variable Embedded X‐Ray Sources in Orion. I. Resolving the Orion Trapezium

We used the High Energy Transmission Grating Spectrometer (HETGS) onboard theChandra X-ray Observatory to perform two observations, separated by threeweeks, of the Orion Trapezium region. The zeroth order images on the AdvancedCCD Imaging Spectrometer (ACIS) provide spatial resolution of 0.5" and moderateenergy resolution. Within a 160"x140" region around the Orion Trapezium weresolve 111 X-ray sources with luminosities between 7x10^{28} ergs/s and2x10^{32} ergs/s. We do not detect any diffuse emission. Many sources appearmuch more heavily absorbed, with N_H in the range of 10^22 to 10^23 cm^-2. Themain objective of this paper is to study the Orion Trapezium and its closevicinity. Most spectra of the very early type members can be fit with atwo-temperature thermal spectrum with a soft component of kT ~ 0.8 keV and ahard component of kT ~ 2 to 3 keV. We discuss these results in the context ofstellar wind models. We detect eight additional, mostly variable X-ray sourcesin the close vicinity of the Trapezium. Five of these X-rays sources areidentified with proplyds and we argue that the X-ray emission originates fromclass I, II and III protostars at the cores of the proplyds.Comment: 12 pages, 3 figures, accepted for publication in The Astrophysical Journa