Elemental Abundances in X-ray Binary Outflows

TL;DR

This study measures elemental abundances in X-ray binary outflows using Chandra spectra, revealing non-solar compositions and potential links to supernova models, thus providing new insights into the origin of ejected material.

Contribution

It introduces two methods for measuring elemental abundances in X-ray binary outflows and compares their effectiveness, highlighting non-solar abundance patterns.

Findings

Outflows show steep AMD favoring high ionization.

Elemental abundances are non-solar and possibly linked to supernova models.

A tentative trend of increasing abundance with atomic number was observed.

Abstract

Line resolved X-ray spectra of outflows from X-ray binaries are interesting since they provide quantifiable measures of the accreted material on to the compact object (black hole or neutron star), which can not be observed directly in the accretion disk. One such measurement that has been largely overlooked is that of the elemental abundances, which potentially provide insights into the origin of the ejected material. Using the Chandra/HETG grating spectrometer we measure and present elemental abundances in four low-mass X-ray binaries. We compare two measurement methods. One is by fitting line series of individual ions and reconstructing the absorption measure distribution (AMD), and the other is a global fit with one or two individual ionization components. All outflows feature a steep AMD strongly favoring high ionization degrees. The present abundances are consistent with previous works suggesting the abundances in the outflows are non-solar. We find a tentative trend of increasing abundances with atomic number, which fits some core-collapse supernova models, but no exact match to a specific one.