Broadband X-ray spectrum of KS 1947+300 with BeppoSAX

We present results obtained from three BeppoSAX observations of the accretion-powered transient X-ray pulsar KS 1947+300 carried out during the declining phase of its 2000 November-2001 June outburst. A detailed spectral study of KS 1947+300 across a wide X-ray band (0.1-100.0 keV) is attempted for the first time here. Timing analysis of the data clearly shows a 18.7 s pulsation in the X-ray light curves in the above energy band. The pulse profile of KS 1947+300 is characterized by a broad peak with sharp rise, followed by a narrow dip. The dip in the pulse profile shows a very strong energy dependence. Broadband pulse phase-averaged spectroscopy obtained with three of the BeppoSAX instruments shows that the energy spectrum in the 0.1-100 keV energy band has three components, a Comptonized component, a ∼0.6 keV blackbody component, and a narrow, weak iron emission line at 6.7 keV with a low column density of material in the line of sight. We place an upper limit of ∼13 eV on the equivalent width of the iron Kα line at 6.4 keV (for a width of 100 eV). Assuming a spherical blackbody emitting region and the distance of the source to be 10 kpc, the radius of the emitting region is found to be in the range 14-22 km, which rules out the inner accretion disk as the soft X-ray-emitting region.