A Study of Interstellar Medium in the Line of Sight of Transient Neutron Star Low-Mass X-ray Binary, MXB 1659-298, by Timing and Spectral Analysis

Abstract

This work is dedicated to the study of interstellar medium (ISM) along the line of sight (LOS) of the transient low-mass X-ray binary, MXB 1659-298, capitalizing the high resolving power of XMM-Newton in the soft energy range. We emphasized the analysis of reflection grating spectrometer (RGS) data in the energy range 0.5–2.15 keV, suitable for the study of ISM. The paper includes an explanation of why, in the soft X-ray energy range, only two observations (out of seven) were deemed eligible for analysis. Three absorption lines associated with highly ionized Fe XX (1s22p2-2p2 (3p) 4d), Si XIV (1s2-1s2p), and Mg XI (1s2-1s6p) were identified in the observations, with IDs of 8620701(2001) and 748391601(2015). These new absorption lines and the absorption edge due to the neutral oxygen K edge seen in the spectra validate the multiphase structure of ISM. The predominance of interstellar medium over the ionized absorber is established along the direction of the source. The equivalent hydrogen column density measured is nearly equal to the galactic HI value derived previously. The small value of the ionic column density of Fe, Si, and Mg in the site of the high-temperature region resembles previous findings.