A Comprehensive Study of Soft X-ray Absorption Features in GX 13+1 Using XMM-Newton Observations

Abstract

In this study, a comprehensive analysis of the reflection grating spectrometer (RGS) data (energy range 0.33 keV to 2.5 keV) of GX 13+1 from the XMM-Newton space observatory was conducted. Numerous absorption lines have been described in earlier publications, although the majority of these investigations focused on the energy range between 3 keV and 10 keV. We considered all ten on-axis observations for spectral analysis, but during timing analysis, off-axis observations were also analysed. A fresh dip in off-axis observation 0122340701(B) was observed together with the previously reported dip in on-axis observation 0505480501(F). No burst or eclipsing was observed in any of the observations. The spectral analysis revealed the presence of the highly ionized elements, Si XIII 1s2–1s2p and 1s2–1s3p transitions with energies of 2.02 keV and 2.24 keV, respectively, as well as Mg XII 1s–6p transitions with energies of 1.91 keV and Al XIII 1s–4p transitions with energies of 2.15 keV. Before this study, no analyses of XMM-Newton data reported Mg XII and Al XIII elements. Moreover, the 1s–6p transitions of Mg XII and 1s–4p transitions of Al XIII were not even reported in any Chandra data analysis. The equivalent hydrogen column densities obtained (2.35 × 1022 cm−2 to 4.18 × 1022 cm−2) are consistent with previously reported values. The equivalent widths of neighbouring observations are found to be nearly the same. This supports us in suggesting that the absorptions may be due to the presence of an interstellar medium (ISM) in the line of sight (LOS) of the source.

Keywords

• GX 13+1
• XMM-Newton
• RGS
• absorption-line
• ISM