SIMBAD references

We present the calibration and background model for the Proportional Counter Array on board the Rossi X-Ray Timing Explorer. The energy calibration is systematics-limited below 10 keV, with deviations from a power-law fit to the Crab Nebula plus pulsar of less than 1%. Unmodeled variations in the instrumental background amount to less than 2% of the observed background below 10 keV and less than 1% between 10 and 20 keV. Individual photon arrival times are accurate to 4.4 µs at all times during the mission and to 2.5 µs after 1997 April 29. The peak pointing direction of the five collimators is known to a precision of a few arcseconds.