Astron. Astrophys. 346, 453-458 (1999)

2. Observation

The Low-Energy Concentrator Spectrometer (LECS) onboard BeppoSAX is an imaging gas scintillation proportional counter sensitive in the energy range 0.1-10.0 keV with a circular field of view of 37´ diameter (Parmar et al. 1997b). Its energy resolution is a factor 2 better than that of the ROSAT Position Sensitive Proportional Counter (PSPC). 1E 0035.4-7230 was observed between 1998 January 4 10:27 and January 6 01:21 UTC. Good data were selected from intervals when the minimum elevation angle above the Earth's limb was 5^o and when the high voltage levels were nominal using the SAXDAS data analysis package. Since the LECS was only operated during satellite night-time, this gave a total on-source exposure of 37 ks.

Examination of the LECS image shows a source at a position consistent with that of 1E 0035.4-7230. A spectrum was extracted centered on the source centroid using a radius of 8´. This radius was chosen to include 95% of the 0.28 keV photons. The spectrum was rebinned to have 20 counts in each bin to allow the use of the statistic. The LECS response matrix from the 1997 September release was used in the spectral analysis. The background spectrum was extracted from the image itself using a semi-annulus centered on 1E 0035.4-7230 with inner and outer radii of 14´ and 19´, respectively. A correction for telescope vignetting was applied (see Parmar et al. 1999). The 1E 0035.4-7230 count rate above background is 0.008 s. Examination of the extracted spectrum shows that the source is only detected in a narrow energy range and only the 21 rebinned channels corresponding to energies between 0.13 and 1.7 keV were used for spectral fitting.

© European Southern Observatory (ESO) 1999

Online publication: May 21, 1999
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