The Araucaria Project. Accurate determination of the dynamical mass of the classical Cepheid in the eclipsing system OGLE-LMC-CEP-1812

TL;DR

This study precisely measures the masses of stars in an eclipsing binary system containing a classical Cepheid, providing crucial data to resolve longstanding discrepancies in Cepheid mass estimates.

Contribution

It presents the most accurate dynamical mass measurement of a classical Cepheid in an eclipsing binary, confirming pulsation model predictions.

Findings

Dynamical masses determined with 1.5% accuracy

Cepheid mass agrees with pulsation models

Improves understanding of Cepheid structure and evolution

Abstract

We have analyzed the double-lined eclipsing binary system OGLE-LMC-CEP-1812 in the LMC and demonstrate that it contains a classical fundamental mode Cepheid pulsating with a period of 1.31 days. The secondary star is a stable giant. We derive the dynamical masses for both stars with an accuracy of 1.5%, making the Cepheid in this system the second classical Cepheid with a very accurate dynamical mass determination, following the OGLE-LMC-CEP-0227 system studied by Pietrzynski et al. (2010). The measured dynamical mass agrees very well with that predicted by pulsation models. We also derive the radii of both components and accurate orbital parameters for the binary system. This new, very accurate dynamical mass for a classical Cepheid will greatly contribute to the solution of the Cepheid mass discrepancy problem, and to our understanding of the structure and evolution of classical Cepheids.