High Resolution Spectroscopy with HETG

Early in the mission a calibration observation will be made of Capella with the HETG and ACIS-S. The simulation of that observation given here serves as a good example of the high resolution spectroscopy that will be possible with Chandra.
The HETG grating spectrum will be dispersed along a shallow "X", each position corresponding to an X-ray energy. The spot in the center is actually an image of the star. The arms of the "X" constitute the dispersed spectrum. (The color coding in this figure matches the ACIS energy in the next figure. Note that lower energies are dispersed more.)
(click for larger image)
A spectrum is provided by ACIS, enabling one to distinguish among ions of different elements. This is the spectrometer of choice in the case of faint or very extended sources.
(click for larger image)
The grating spectrum further probes each of these X-ray regions, revealing individual X-ray lines emitted by each of these elements. (To examine the grating spectrum associated with the other regions, click on the previous figure and then click on the desired box.)
(click for larger image)
The ratios of line fluxes of the same ion depend on temperature and density, while those of different ions give information about the ionization state. One can further investigate chemical composition and abundance by using lines and line blends from different elements.

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Revised 7/24/99;
(relocated 8/9/2004.)