Determining the Distance of Cyg X-3 with its X-ray Dust Scattering Halo

TL;DR

This study estimates the distance to Cyg X-3 using its X-ray dust scattering halo and cross-correlation analysis, revealing the distance depends on the assumed location of Cygnus OB2 and can be refined with future measurements.

Contribution

The paper introduces a novel method to determine Cyg X-3's distance using X-ray dust scattering halos and cross-correlation, with results less sensitive to dust properties.

Findings

Estimated distance to Cyg X-3 varies with Cygnus OB2 distance assumptions.

Distance estimates range from 3.4 to 9.3 kpc depending on Cygnus OB2 distance.

Method shows weak dependence on dust grain properties and photon energy.

Abstract

Using a cross-correlation method, we study the X-ray halo of Cyg X-3. Two components of dust distributions are needed to explain the time lags derived by the cross-correlation method. Assuming the distance as 1.7 kpc for Cygnus OB2 association (a richest OB association in the local Galaxy) and another uniform dust distribution, we get a distance of $7.2^{+0.3}_{-0.5}$ kpc (68$%$ confidence level) for Cyg X-3. When using the distance estimation of Cygnus OB2 as 1.38 kpc or 1.82 kpc, the inferred distance for Cyg X-3 is $3.4^{+0.2}_{-0.2}$ kpc or $9.3^{+0.6}_{-0.4}$ kpc respectively. The distance estimation uncertainty of Cyg X-3 is mainly related to the distance of the Cygnus OB2, which may be improved in the future with high precision astrometric measurements. The advantage of this method is that the result depends weakly on the photon energy, dust grain radius, scattering cross-section and so on.