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P. S. Ray, K. S. Wood, M. T. Wolff, M. N. Lovellette (NRL), S. Sheikh (UMD), D.-S. Moon, S. S. Eikenberry (Cornell), M. Roberts, A. Lyne, C. Jordon (Jodrell Bank), E. D. Bloom, D. Tournear, P. Saz Parkinson, K. Reilly (SLAC)
We update the status of the absolute time calibration of the USA Experiment as determined by observations of X-ray emitting rotation-powered pulsars. The brightest such source is the Crab Pulsar and we have obtained observations of the Crab at radio, IR, optical, and X-ray wavelengths. We directly compare arrival time determinations for 2--10 keV X-ray observations made contemporaneously with the PCA on the Rossi X-ray Timing Explorer and the USA Experiment on ARGOS. These two X-ray measurements employ very different means of measuring time and satellite position and thus have different systematic error budgets. The comparison with other wavelengths requires additional steps such as dispersion measure corrections and a precise definition of the ``peak'' of the light curve since the light curve shape varies with observing wavelength. We will describe each of these effects and quantify the magnitude of the systematic error that each may contribute. We will also include time comparison results for other pulsars, such as PSR B1509-58 and PSR B1821-24. Once the absolute time calibrations are well understood, comparing absolute arrival times at multiple energies can provide clues to the magnetospheric structure and emission region geometry.
Basic research on X-ray Astronomy at NRL is funded by NRL/ONR.
Bulletin of the American Astronomical Society,
© 2003. The American Astronomical Soceity.