# Spectroscopic modelling of four neutron star low-mass X-ray binaries using CLOUDY

## TL;DR

This study models four neutron star low-mass X-ray binaries using CLOUDY to analyze their spectral lines, revealing physical conditions and estimating magnetic field strengths in their accretion discs.

## Contribution

It provides detailed spectral modelling of LMXBs with CLOUDY, incorporating magnetic field effects to estimate upper limits of magnetic fields in accretion discs.

## Key findings

- Estimated magnetic field upper limits of a few hundred to a few thousand G.
- Identified key physical parameters like density and metallicity in accretion discs.
- Analyzed spectral line modifications due to magnetic fields.

## Abstract

Low-mass X-ray binaries (LMXBs) have a wide range of X-ray properties which can be utilised to reveal many physical conditions of the associated accretion discs. We use the spectral synthesis code CLOUDY to perform a detailed modelling of neutron star LMXBs GX 13+1, MXB 1659--298, 4U 1323--62 and XB 1916--053; and characterise the underlying physical conditions, such as density, radiation field, metallicity, wind velocity, etc. For this purpose we model highly ionised spectra of Fe, Ca, S, Si, Mg, Al in the soft X-ray band, and compare the predicted line flux ratios with the observed values. We also find that the strength and profile of these spectral lines get modified in the presence of magnetic field in the accretion disc. Using this, we estimate an upper limit of the existing magnetic field to be about a few hundred to a few thousand G in the accretion discs of these four LMXBs.