Constellation-X Effective Area
The fundamental mission requirement is to acquire spectra of high statistical quality in an observing time of ~103 to 106 s. For many astronomical sources, short-term variations in the X-ray spectra provide a crucial key to the underlying physics. For stellar flares, the timescales of interest are of order tens of seconds, while for active galactic nuclei, they are several hours. Variability studies require both large collecting area and continuous coverage. These requirements dictate an effective area (including the spectrometer efficiency) of ~15,000 cm2 at 1.25 keV and ~6,000 cm2 at 6 keV, resulting in 100 times the throughput for high resolution spectroscopy of previous X-ray observatories.
The large collecting area is achieved with a design utilizing several mirror modules, each with its own spectrometer/detector system.
The effective area of Constellation-X for high resolution spectroscopy is a factor of 100 times larger than the XMM-Newton gratings (0.6-2.0 keV) or the Chandra gratings (0.25-10 keV).
A Constellation-X simulation of an 80,000 s exposure of AR Lac illustrates key helium-like transitions that will be used to determine plasma density and temperature. Clearly resolved in all cases are the resonance, forbidden, and intercombination lines. The Fe XXV simulation utilizes the X-ray Microcalorimeter Spectrometer (XMS) while the others utilize an example implementation of the X-ray Grating Spectrometer (XGS).
