X-ray Spectroscopy of MXB 1728-34 with XMM-Newton

TL;DR

This study analyzes XMM-Newton data of MXB 1728-34, revealing a broad iron emission line and providing estimates of the inner disk radius and system inclination during a low luminosity state.

Contribution

First detailed spectral analysis of MXB 1728-34 with reflection modeling to determine accretion disk parameters.

Findings

Detection of a broad iron emission line at 6-7 keV.

Inner disk radius estimated between 25-100 km.

System inclination inferred between 44° and 60°.

Abstract

We have analysed an XMM-Newton observation of the low mass X-ray binary and atoll source MXB 1728-34. The source was in a low luminosity state during the XMM-Newton observation, corresponding to a bolometric X-ray luminosity of 5*10E36 d^2 erg/s, where d is the distance in units of 5.1 kpc. The 1-11 keV X-ray spectrum of the source, obtained combining data from all the five instruments on-board XMM-Newton, is well fitted by a Comptonized continuum. Evident residuals are present at 6-7 keV which are ascribed to the presence of a broad iron emission line. This feature can be equally well fitted by a relativistically smeared line or by a self-consistent, relativistically smeared, reflection model. Under the hypothesis that the iron line is produced by reflection from the inner accretion disk, we can infer important information on the physical parameters of the system, such as the inner disk radius, Rin = 25-100 km, and the inclination of the system, 44{\deg} < i < 60{\deg}.