Identification of High Mass X-ray Binaries selected from XMM-Newton observations of the LMC

TL;DR

This study identifies and confirms nine new high mass X-ray binaries in the Large Magellanic Cloud using X-ray, optical spectroscopy, and light curve analysis, significantly expanding known Be/X-ray binary populations.

Contribution

It introduces a new method combining X-ray data with optical spectroscopy and timing analysis to discover and confirm new high mass X-ray binaries in the LMC.

Findings

Nine new Be/X-ray binaries identified and confirmed.

Substantial increase in the known Be/X-ray binary population in the LMC.

Optical properties of the new systems characterized.

Abstract

The Large Magellanic Cloud (LMC) currently hosts around 23 high mass X-ray binaries (HMXBs) of which most are Be/X-ray binaries. The LMC XMM-Newton survey provided follow-up observations of previously known X-ray sources that were likely HMXBs, as well as identifying new HMXB candidates. In total 19 candidate HMXBs were selected based on their X-ray hardness ratios. In this paper we present red and blue optical spectroscopy, obtained with SALT and the SAAO 1.9-m telescope, plus a timing analysis of the long term optical light curves from OGLE to confirm the nature of these candidates. We find that 9 of the candidates are new Be/X-ray Binaries, substantially increasing the LMC Be/X-ray binary population. Furthermore, we present the optical properties of these new systems, both individually and as a group of all the BeXBs identified by the XMM-Newton survey of the LMC.