A detailed study of the modulation of the optical light from Sk160/SMC X-1

TL;DR

This study analyzes eight years of optical data from OGLE-III to examine the light modulation in the SMC X-1 system, revealing binary and superorbital period modulations linked to the accretion disk precession.

Contribution

It provides the first evidence of superorbital modulation in optical light from SMC X-1, enhancing understanding of accretion disk dynamics in high mass X-ray binaries.

Findings

Optical light modulates at the binary period of 3.9 days.

First detection of superorbital modulation in optical light.

Insights into the sources of optical emission in the system.

Abstract

Eight years of optical photometry from OGLE-III are presented of the optical counterpart to the High Mass X-ray Binary system, SMC X-1. The optical data provide the best view to date of the modulation of the light from the system at the binary period of 3.9d. In addition, it is shown for the first time that the light is also modulated at the superorbital period - a period associated with the precessing of a warped accretion disk around the neutron star partner. The implications for the sources of the various components of the optical light in this system are discussed.