Chandra Orion Ultradeep Project
Observations

The Chandra X-ray reflecting mirrors provide superb arcsecond-imaging, and the ACIS detector have very high efficiency and low noise.  The combination allows detection and study of 1616 sources in the Orion Nebula, one of the richest X-ray fields ever studied. The COUP data analysis is based on the sophisticated ACIS Extract software package and incorporates the latest techniques: sub-pixel resolution, sensitive source detection across the field, optimal event extraction, positional accuracies of +/- 0.2"-0.4", self-consistent treatment of piled-up sources, automatic spectral and variability analysis, and cross-correlation with the latest star catalogs. 

The image above summarizes what we know about each of the 1616 COUP sources. The top panel shows the lightcurve where brightness (Y axis) is plotted against time (13.2 days).  The second panel shows each photon's arrival time and energy from 0.5 to 8 keV.  The bottom left panels show the X-ray image around the source, smoothed and overplotted with known stars.  The bottom right panel shows the spectrum with a hot plasma model.  The bottom numbers  give the extensive quantitative information provided by ACIS Extract.

Here is the center of the Orion Nebula field; this portion covers 3'x3' (the full Moon, for comparison, covers 30'x30')..  The brightest source, by far, is the ~45 solar mass O star theta1 Ori C.   The faintest sources have only 5 counts, or one photon arriving every ~2 days.  Chandra can detect sources even when heavily obscured by the Orion molecular cloud up to visual absorption of AV=500 magnitudes.

The full paper on the COUP observations is:
"Chandra Orion Ultradeep Project: Observations and source lists" by K. V. Getman, E. Flaccomio, P. S. Broos, N. Grosso, M. Tsujimoto, L. Townsley, G. P. Garmire, J. Kastner, J. Li, F. R. Harnden Jr,, S. Wolk, S. S. Murray, C. J. Lada, A. A. Muench, M. J. McCaughrean, G. Meeus, F. Damiani, G. Micela, S. Sciortino, J. Bally, L. A. Hillenbrand, W.
Herbst, T. Preibisch, E. D. Feigelson, Astrophys. J. Suppl., in press (2005)

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