X-ray spectroscopic study of the ADC source X1822-371

Abstract

We analyse two Chandra HETGS (High Energy Transmission Grating Spectrometer) observations and one XMM-Newton observation. The HETGS and XMM/Epic-pn observed X 1822-371 for 140 and 50 ks, respectively. We extracted an averaged spectrum and five spectra from five selected orbital-phase intervals that are 0.04-0.25, 0.25-0.50, 0.50-0.75, 0.95-1.04; the orbital phase zero corresponds to the eclipse time. The spectra cover the energy band between 0.4 and 12 keV. We confirm the presence of local neutral matter that partially covers the X-ray emitting region; the equivalent hydrogen column is 3.5 × 1022 cm-2 and the covered fraction is around 60 %. We detected and identified several emission lines associated with He-like and H-like ions. The He-like transitions of O vu, Ne ix, Mg xi, Si xm show that the intercombination dominates over the forbidden and resonance lines. The fluxes of the lines are higher during the orbital-phase interval 0.04-0.75 while their intensities decrease during the dip and the eclipse. We discuss the presence of an optically thin corona with optical depth of 0.01 that scatters the luminosity from the inner region indetyfing it with the hot corona showed by [12] in the disc illuminated by a central sources. © Copyright owned by the author(s) under the terms of the Creative Commons Attribution-NonCommercial-ShareAlike Licence.