BeppoSAX Low-Energy Concentrator Spectrometer background subtraction techniques

We present 3 methods for the subtraction of non-cosmic and unresolved cosmi c backgrounds observed by the Low-Energy Concentrator Spectrometer (LECS) o n-board BeppoSAX. Removal of these backgrounds allows a more accurate model ing of the spectral data from point and small-scale extended sources. At hi gh (>\25\degrees) galactic latitudes, subtraction using a standard backgrou nd spectrum works well. At low galactic latitudes, or in complex regions of the X-ray sky, two alternative methods are presented. The first uses count s obtained from two semi-annuli near the outside of the LEGS field of view to estimate the background at the source location. The second method uses R OSAT Position Sensitive Proportional Counter (PSPC) all-sky survey data to estimate the LEGS background spectrum for a given pointing position. A comp arison of the results from these methods provides an estimate of the system atic uncertainties. For high galactic latitude fields, all 3 methods give 3 sigma confidence uncertainties of <0.9 10(-3) count s(-1) (0.1- 10 keV), o r <1.5 10(-3) count s(-1) (0.1- 2 keV). These correspond to 0.1 - 2.0 keV f luxes of 0.7 - 1.8 and 0.5 - 1.1 10(-13) erg cm(-2) s(-1) for a power-law s pectrum with a photon index of 2 and photoelectric absorption of 3 10(20) a nd 3 10(21) atom cm(-2), respectively. At low galactic latitudes, or in com plex regions of the X-ray sky, the uncertainties are a factor similar to 2. 5 higher.