Estimating The Background Spectrum Of RXTE-HEXTE's Cluster A
Abstract
The High Energy X-ray Timing Experiment (HEXTE) on-board the Rossi X-ray Timing Explorer (RXTE) consists of two clusters (``A'' and ``B'') of 4 NaI/CsI phoswich scintillation detectors which are sensitive to X-rays from 15 to 250 keV. Since the launch of RXTE in 1995 HEXTE mostly operated in its standard ``rocking'' mode where the pointing direction of each of the two clusters alternates between source and background measurements every 16 or 32 seconds in such a way that one cluster is always looking at the source while the other samples the background (offsets alternate between opposite sides from the source). During the extraction of source light curves and spectra each cluster uses its own background measurements to perform the background correction.
Starting in 2005 December the rocking mechanism of cluster A began to display increasingly frequent interruptions. While cluster B is continuing to perform the standard rocking, cluster A is now permanently fixed in the on-source staring position for all observations since 2006 July 13, i.e., there are no direct quasi-simultaneous background measurements for cluster A. We have developed a prototype FTOOL which for a given observation uses the background spectrum measured by cluster B to produce an estimated cluster A background spectrum. The tool uses a set of channel dependent parameters to perform a linear transformation of the count rates in each spectral channel. In this poster we explain how these parameters were derived from archived background measurements, compare estimated and measured cluster A spectra for archived rocking observations, and present an example of the application of the method to a recent cluster A staring observation.- Publication:
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AAS/High Energy Astrophysics Division #9
- Pub Date:
- September 2006
- Bibcode:
- 2006HEAD....9.1821P