Hard X-ray colours of Neutron Star and Black Hole Low Mass X-ray Binaries with INTEGRAL

TL;DR

This study uses INTEGRAL data to analyze hard X-ray colour-colour diagrams of low mass X-ray binaries, aiming to distinguish neutron star and black hole systems through spectral variability patterns.

Contribution

It introduces a systematic comparison of X-ray colour-colour diagrams between neutron star and black hole LMXBs using INTEGRAL data and a moments analysis method.

Findings

Potential differences in C-C diagram patterns between NS and BH LMXBs

Use of moments analysis to quantify spectral variability

First systematic comparison in the hard X-ray domain above 20 keV

Abstract

The X-ray spectra of Low Mass X-ray Binaries (LMXB) can change on short time-scales, making it difficult to follow their spectral characteristics in detail through model fitting. Colour-colour (C-C) diagrams are therefore often used as alternative, model independent, tools to study the spectral variability of these sources. The INTEGRAL mission, with its high sensitivity, large field of view and good angular resolution, is well suited to study the hard X-ray properties of LMXBs. In particular the ISGRI imager on board of INTEGRAL allows the regular monitoring of the sources in the less frequently studied domain above 20 keV. In this proceeding, C-C diagrams have been made with data from the INTEGRAL public archive; a search is made for systematic differences in the C-C diagrams between black hole candidates (BH) and neutron stars (NS) in LMXBs using a moments analysis method.