The paper that the ESO PR is based on is a Research Letter to the journal Nature, "The dynamical mass of a classical Cepheid variable star in an eclipsing binary system", with G. Pietrzynski, I. B. Thompson, W. Gieren, D. Graczyk, G. Bono, A. Udalski, I. Soszynski, D. Minniti, and B. Pilecki as authors (the link is the same as in the ESO PR, to a PDF).
Here is the abstract:
Pietrzynski et al. wrote:Stellar pulsation theory provides a means of determining the masses of pulsating classical Cepheid supergiants—it is the pulsation that causes their luminosity to vary. Such pulsational masses are found to be smaller than the masses derived from stellar evolution theory: this is the Cepheid mass discrepancy problem1,2, for which a solution is missing3–5.An independent, accurate dynamical mass determination for a classical Cepheid variable star (as opposed to type-II Cepheids, low-mass stars with a very different evolutionary history) in a binary system is needed in order to determine which is correct. The accuracy of previous efforts to establish a dynamical Cepheid mass from Galactic single-lined non-eclipsing binaries was typically about 15–30 per cent (refs 6, 7), which is not good enough to resolve the mass discrepancy problem. In spite of many observational efforts8,9, no firm detection of a classical Cepheid in an eclipsing double-lined binary has hitherto been reported. Herewe report the discovery of a classical Cepheid in a well detached, double-lined eclipsing binary in the Large Magellanic Cloud. We determine the mass to a precision of one per cent and show that it agrees with its pulsation mass, providing strong evidence that pulsation theory correctly and precisely predicts the masses of classical Cepheids.