Detection of Spectral Lines

Because of the high resolution ( $\Delta~E \sim 1--5$ eV) of the OXS, the number of events per energy bin in typical 10⁴ second OXS scans due to background and source continuum is expected to be $\mathrel{\copy\simlessbox} 1$. Rough estimates of the total number of events in lines of interest, using effective areas in Figure 55 , can be used to determine the feasibility of OXS observations.

Future tools for determining OXS rates and simulating OXS spectra and energy-resolved images will be available from the WWW sites http://uhuru.dsri.dk/srg/srg.html at DSRI and http://hea-www.harvard.edu/SXG/sxg.html at the U.S. SXG Coordination Facility.

  

Figure 55: OXS Effective Area

  

Figure 56: An extended source emitting a He-like line series can be mapped in each spectral feature by combining data from a series of observations, each with a slightly different orientation of the crystal panel and telescope pointing direction. In any one orientation, specific regions of the source, as shown here, will satisfy the Bragg conditions for the Forbidden, Intercombination, and Resonance line energies and thus be imaged into corresponding regions on the detector. Different crystal/telescope orientations will sample different regions of the source.