The Araucaria Project: The first-overtone classical Cepheid in the eclipsing system ogle-LMC-CEP-2532

Journal Article · Wed Jun 10 04:00:00 EDT 2015 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/806/1/29· OSTI ID:22883100

Pilecki, Bogumił; Pietrzyński, Grzegorz; Udalski, Andrzej; Soszyński, Igor; Konorski, Piotr ^[1]; Graczyk, Dariusz; Gieren, Wolfgang; Taormina, Mónica; Gallenne, Alexandre ^[2]; Thompson, Ian B. ^[3]; Smolec, Radosław ^[4]; Minniti, Dante; Catelan, Márcio ^[5]

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1. Warsaw University Observatory, Al. Ujazdowskie 4, PL-00-478, Warszawa (Poland)
2. Universidad de Concepción, Departamento de Astronomía, Casilla 160-C, Concepción (Chile)
3. Carnegie Observatories, 813 Santa Barbara Street, Pasadena, CA 91101-1292 (United States)
4. Copernicus Astronomical Centre, Polish Academy of Sciences, Bartycka 18, 00-716 Warsaw (Poland)
5. Millenium Institute of Astrophysics, Santiago (Chile)

We present here the first spectroscopic and photometric analysis of the double-lined eclipsing binary containing the classical, first-overtone (FO) Cepheid OGLE-LMC-CEP-2532 (MACHO 81.8997.87). The system has an orbital period of 800 days and the Cepheid is pulsating with a period of 2.035 days. Using spectroscopic data from three high-class telescopes and photometry from three surveys spanning 7500 days, we are able to derive the dynamical masses for both stars with an accuracy better than 3%. This makes the Cepheid in this system one of a few classical Cepheids with an accurate dynamical mass determination (M{sub 1}=3.90±0.10 M{sub ⊙}). The companion is probably slightly less massive (3.82±0.10 M{sub ⊙}), but may have the same mass within errors (M{sub 2}/M{sub 1}=0.981±0.015). The system has an age of about 185 million years and the Cepheid is in a more advanced evolutionary stage. For the first time precise parameters are derived for both stars in this system. Due to the lack of the secondary eclipse for many years, not much was known about the Cepheid’s companion. In our analysis, we used extra information from the pulsations and the orbital solution from the radial velocity curve. The best model predicts a grazing secondary eclipse shallower than 1 mmag, hence undetectable in the data, about 370 days after the primary eclipse. The dynamical mass obtained here is the most accurate known for a FO Cepheid and will contribute to the solution of the Cepheid mass discrepancy problem.

• OSTI ID: 22883100
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 1 Vol. 806; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United Kingdom
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
CEPHEIDS
GALAXIES
MASS
OSCILLATIONS
PHOTOMETRY
RADIAL VELOCITY
TELESCOPES