An empirical method to estimate the LMC distance using B-stars in eclipsing binary systems

¹ Astrophysics Research Institute, Liverpool John Moores University, Twelve Quays House, Egerton Wharf, Birkenhead CH41 1LD, UK
² Max-Planck-Institut für Astrophysik, Karl-Schwarzschild-Straße 1, 85748 Garching, Germany
³ Instituut voor Sterrenkunde, PACS-ICC, Celestijnenlaan 200B, 3001 Heverlee, Belgium
⁴ European Southern Observatory, EIS-team, Karl-Schwarzschild-Straße 2, 85740 Garching, Germany

Corresponding author: M. Salaris, ms@astro.livjm.ac.uk

Received: 22 August 2001
Accepted: 29 October 2001

Abstract

We present a new method to determine the distance to B-stars in eclipsing binary systems. The method is completely empirical, and it is based on the existence of a very tight linear relationship between the V-band “zero magnitude angular diameter” and the Strömgren colour index c₁ for B-stars; we have empirically calibrated this relationship using local single B-stars with accurate angular diameters, and B-stars in eclipsing binaries with precise radii and parallax determinations. By studying the differential behaviour of this relationship as predicted by theoretical stellar evolution models, we find that it is independent of the stellar metallicities for a range of [Fe/H] values between the solar one and that of young stars in the Magellanic Clouds. The method, which also provides the value of the reddening to the system, is discussed in detail, together with a thorough estimate of the associated errors. We conclude that accurate Strömgren photometry obtainable with 1.5 m-class telescopes of the LMC eclipsing binaries HV 2274 and HV 982 will allow to obtain an empirical LMC distance with an accuracy of the order of 0.13 mag.