The Araucaria project: A study of the classical cepheid in the eclipsing binary system OGLE LMC562.05.9009 in the large magellanic cloud

Wolfgang Gieren, Bogumił Pilecki, Grzegorz Pietrzyński, Dariusz Graczyk, Andrzej Udalski, Igor Soszyński, Ian B. Thompson, Pier Giorgio Prada Moroni, Radosław Smolec, Piotr Konorski, Marek Górski, Paulina Karczmarek, Ksenia Suchomska, Mónica Taormina, Alexandre Gallenne, Jesper Storm, Giuseppe Bono, Márcio Catelan, Michał Szymański, Szymon KozłowskiPaweł Pietrukowicz, Łukasz Wyrzykowski, Radosław Poleski, Jan Skowron, Dante Minniti, K. Ulaczyk, P. Mróz, M. Pawlak, Nicolas Nardetto

Research output: Contribution to journalArticlepeer-review

27 Citations (Scopus)


We present a detailed study of the classical Cepheid in the double-lined, highly eccentric eclipsing binary system OGLE-LMC562.05.9009. The Cepheid is a fundamental mode pulsator with a period of 2.988 days. The orbital period of the system is 1550 days. Using spectroscopic data from three 4-8-m telescopes and photometry spanning 22 years, we were able to derive the dynamical masses and radii of both stars with exquisite accuracy. Both stars in the system are very similar in mass, radius, and color, but the companion is a stable, non-pulsating star. The Cepheid is slightly more massive and bigger (M1 = 3.70 ± 0.03 Mo, R1 = 28.6 ± 0.2 Ro) than its companion (M2 = 3.60 ± 0.03 Mo, R2 = 26.6 ± 0.2 Ro). Within the observational uncertainties both stars have the same effective temperature of 6030 ± 150 K. Evolutionary tracks place both stars inside the classical Cepheid instability strip, but it is likely that future improved temperature estimates will move the stable giant companion just beyond the red edge of the instability strip. Within current observational and theoretical uncertainties, both stars fit on a 205 Myr isochrone arguing for their common age. From our model, we determine a value of the projection factor of p = 1.37 ± 0.07 for the Cepheid in the OGLE-LMC562.05.9009 system. This is the second Cepheid for which we could measure its p-factor with high precision directly from the analysis of an eclipsing binary system, which represents an important contribution toward a better calibration of Baade-Wesselink methods of distance determination for Cepheids.

Original languageEnglish
Article number28
JournalAstrophysical Journal
Issue number1
Publication statusPublished - 10 Dec 2015


  • binaries: eclipsing
  • galaxies: individual (LMC)
  • stars: oscillations
  • stars: variables: Cepheids

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


Dive into the research topics of 'The Araucaria project: A study of the classical cepheid in the eclipsing binary system OGLE LMC562.05.9009 in the large magellanic cloud'. Together they form a unique fingerprint.

Cite this