Towards early-type eclipsing binaries as extragalactic milestones: II. NLTE spectral analysis and stellar parameters of the detached O-type system OGLE-LMC-ECL-06782 in the LMC

Understand

We combine the NLTE spectral analysis of the detached O-type eclipsing binary OGLE-LMC-ECL-06782 with the analysis of the radial velocity curve and light curve to measure an independent distance to the LMC.

• In our spectral analysis we study composite spectra of the system at quadrature and use the information from radial velocity and light curve about stellar gravities, radii and component flux ratio to derive effective temperature, reddening, extinction and intrinsic surface brightness.
• We obtain a distance modulus to the LMC of m - M = 18.53 +/- 0.04 mag.
• This value is 0.05 mag larger than the precision distance obtained recently from the analysis of a large sample of detached, long period late spectral type eclipsing binaries but agrees within the margin of the uncertainties.