A study of the spectral evolution during dipping in XB 1323-619 with Rossi-XTE and BeppoSAX

We report results from analysis of the observations of the dipping low mass X-ray binary XB 1323-619 made with BeppoSAX and Rossi-XTE. The dust-scatte red halo contributes significantly in this source, and the observation made with BeppoSAX on 1997 August was used to provide MECS radial intensity pro files at several energies. From these, the halo fractions were obtained and thus an optical depth to dust scattering of 1.8 +/- 0.4 derived. In the Ro ssi-XTE observation of April 25-28, 1997, seven X-rays dips were observed t ogether with 7 bursts repeating approximately periodically. Non-dip and dip PCA spectra can be well-described by assuming the emission consists of poi nt-like blackbody emission identified with the neutron star, plus Comptoniz ed emission from an extended ADC. The blackbody temperature is 1.79 +/- 0.2 1 keV and the cut-off power law photon index 1.61 +/- 0.04. Spectral evolut ion in dipping is well described by progressive covering of the extended Co mptonizing region by absorber plus more rapid removal of the point-like bla ckbody. The effects of dust scattering and of the X-ray pulsar 1SAXJ1324.4- 6200 also in the field of view are included in the fitting. We detect an ir on line at similar to6.4 keV and its probable origin in the ADC is discusse d.