The Useable Exposure Times

Observations with small filtered exposures ($\sim5$ ks or less) are likely to be problematic due to the limited number of events in the unexposed corners of the detectors (decent statistics are needed for accurate background modeling). Exposures in the $\sim5-10$ ks range can also be problematic, particularly for the pn, with the QPB being over- or under-subtracted. When the QPB is under-subtracted the fitting of the SP component can correct for this effect, but in an uncertain manner with unknown systematics. We expect significant improvements with the next iteration of ESAS.