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Astron. Astrophys. 330, 175-180 (1998)

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2. Observations

Results from the the Low-Energy Concentrator Spectrometer (LECS; 0.1-10 keV; Parmar et al. 1997) and Medium-Energy Concentrator Spectrometer (MECS; 1.3-10 keV; Boella et al. 1997) on-board BeppoSAX are presented. The MECS consists of three identical grazing incidence telescopes with imaging gas scintillation proportional counters in their focal planes. The LECS uses an identical concentrator system as the MECS, but utilizes an ultra-thin (1.25  [FORMULA] m) entrance window and a driftless configuration to extend the low-energy response to 0.1 keV. The fields of view (FOV) of the LECS and MECS are circular with diameters of [FORMULA] and [FORMULA], respectively. In the overlapping energy range, the position resolution of both instruments is similar and corresponds to 90% encircled energy within a radius of 2:05 at 1.5 keV. At lower energies, the encircled energy is proportional to [FORMULA]. The LECS 0.1-10 keV background counting rate is [FORMULA]  arcmin-2  s-1.

The region of sky containing 1E 2259+586 and G109.1-1.0 was observed by BeppoSAX between 1996 November 16 03:32 and November 17 05:19 UTC. Good data were selected from intervals when the minimum elevation angle above the Earth's limb was [FORMULA] [FORMULA] and when the instrument configurations were nominal using the SAXDAS 1.1.0 data analysis package. This gives exposures of 53.4 ks for the MECS and 15.2 ks for the LECS, which was only operated during satellite night-time. The LECS and MECS images, smoothed using a Gaussian filter of width 1:05, are shown in Fig. 1. 1E 2259+586 is visible as a point source close to the center of both images. The position of 1E 2259+586 derived by summing the LECS and the MECS data is 23 [FORMULA], [FORMULA]   [FORMULA]   [FORMULA] (J2000.0) with a 68% confidence uncertainty radius of [FORMULA]. This is consistent with the Einstein High Resolution Imager position of Fahlman et al. (1982). The SNR is visible as extended emission throughout both images.

[FIGURE] Fig. 1. LECS (left panel) 0.5-2.0 keV and MECS (right panel) 2.0-8.0 keV smoothed images of the region containing 1E 2259+586 and G109.1-1.0. The contours levels represent 1, 2, 3, 6, 12, 25 and 50% of the peak flux of each image. The "cut-outs" at the upper-left and lower-right of the MECS image are due to the removal of instrument calibration source events. The softness of the SNR and lobe can be seen by the greater asymmetry of the LECS contours, compared to the MECS. The extraction region used for the SNR shell spectrum is indicated by the heavy dotted line, minus the box shaped region (which is the extraction region for the lobe spectrum)

Separate spectra were extracted for the pulsar, SNR shell and X-ray lobe regions. All spectra were rebinned to have [FORMULA] 20 counts in each bin to allow the use of [FORMULA] statistics. Background subtraction was performed using standard blank field exposures.

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© European Southern Observatory (ESO) 1998

Online publication: January 8, 1998