Physical parameters and the projection factor of the classical Cepheid in the binary system OGLE-LMC-CEP-0227

B. Pilecki, D. Graczyk, G. Pietrzynski, W. Gieren, I. B. Thompson, W. L. Freedman, V. Scowcroft, B. F. Madore, A. Udalski, I. Soszynski, P. Konorski, R. Smolec, N. Nardetto, G. Bono, P. G. Prada Moroni, J. Storm, A. Gallenne

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Abstract

A novel method of analysis of double-lined eclipsing binaries containing a radially pulsating star is presented. The combined pulsating–eclipsing light curve is built up from a purely eclipsing light-curve grid created using an existing modelling tool. For every pulsation phase, the instantaneous radius and surface brightness are taken into account, being calculated from the disentangled radial velocity curve of the pulsating star and from its out-of-eclipse pulsational light curve and the light ratio of the components, respectively. The best model is found using the Markov chain Monte Carlo method. The method is applied to the eclipsing binary Cepheid OGLE-LMC-CEP-0227 (Ppuls = 3.80 d, Porb = 309 d). We analyse a set of new spectroscopic and photometric observations for this binary, simultaneously fitting OGLE V-band, I-band and Spitzer 3.6 μm photometry. We derive a set of fundamental parameters of the system significantly improving the precision comparing to the previous results obtained by our group. The Cepheid mass and radius are M1 = 4.165 ± 0.032 M⊙ and R1 = 34.92 ± 0.34 R⊙, respectively. For the first time a direct, geometrical and distance-independent determination of the Cepheid projection factor is presented. The value p = 1.21 ± 0.03(stat.) ± 0.04(syst.) is consistent with theoretical expectations for a short-period Cepheid and interferometric measurements for δ Cep. We also find a very high value of the optical limb darkening coefficients for the Cepheid component, in strong disagreement with theoretical predictions for static atmospheres at a given surface temperature and gravity.
Original languageEnglish
Pages (from-to)953-967
JournalMonthly Notices of the Royal Astronomical Society
Volume436
Issue number2
DOIs
Publication statusPublished - 1 Dec 2013

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light curve
projection
limb darkening
stars
radii
Markov chains
eclipses
extremely high frequencies
radial velocity
surface temperature
photometry
Monte Carlo method
brightness
Markov chain
grids
gravitation
limb
atmospheres
curves
coefficients

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Pilecki, B., Graczyk, D., Pietrzynski, G., Gieren, W., Thompson, I. B., Freedman, W. L., ... Gallenne, A. (2013). Physical parameters and the projection factor of the classical Cepheid in the binary system OGLE-LMC-CEP-0227. Monthly Notices of the Royal Astronomical Society, 436(2), 953-967. https://doi.org/10.1093/mnras/stt1529

Physical parameters and the projection factor of the classical Cepheid in the binary system OGLE-LMC-CEP-0227. / Pilecki, B.; Graczyk, D.; Pietrzynski, G.; Gieren, W.; Thompson, I. B.; Freedman, W. L.; Scowcroft, V.; Madore, B. F.; Udalski, A.; Soszynski, I.; Konorski, P.; Smolec, R.; Nardetto, N.; Bono, G.; Prada Moroni, P. G.; Storm, J.; Gallenne, A.

In: Monthly Notices of the Royal Astronomical Society, Vol. 436, No. 2, 01.12.2013, p. 953-967.

Research output: Contribution to journalArticle

Pilecki, B, Graczyk, D, Pietrzynski, G, Gieren, W, Thompson, IB, Freedman, WL, Scowcroft, V, Madore, BF, Udalski, A, Soszynski, I, Konorski, P, Smolec, R, Nardetto, N, Bono, G, Prada Moroni, PG, Storm, J & Gallenne, A 2013, 'Physical parameters and the projection factor of the classical Cepheid in the binary system OGLE-LMC-CEP-0227', Monthly Notices of the Royal Astronomical Society, vol. 436, no. 2, pp. 953-967. https://doi.org/10.1093/mnras/stt1529
Pilecki, B. ; Graczyk, D. ; Pietrzynski, G. ; Gieren, W. ; Thompson, I. B. ; Freedman, W. L. ; Scowcroft, V. ; Madore, B. F. ; Udalski, A. ; Soszynski, I. ; Konorski, P. ; Smolec, R. ; Nardetto, N. ; Bono, G. ; Prada Moroni, P. G. ; Storm, J. ; Gallenne, A. / Physical parameters and the projection factor of the classical Cepheid in the binary system OGLE-LMC-CEP-0227. In: Monthly Notices of the Royal Astronomical Society. 2013 ; Vol. 436, No. 2. pp. 953-967.
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T1 - Physical parameters and the projection factor of the classical Cepheid in the binary system OGLE-LMC-CEP-0227

AU - Pilecki, B.

AU - Graczyk, D.

AU - Pietrzynski, G.

AU - Gieren, W.

AU - Thompson, I. B.

AU - Freedman, W. L.

AU - Scowcroft, V.

AU - Madore, B. F.

AU - Udalski, A.

AU - Soszynski, I.

AU - Konorski, P.

AU - Smolec, R.

AU - Nardetto, N.

AU - Bono, G.

AU - Prada Moroni, P. G.

AU - Storm, J.

AU - Gallenne, A.

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N2 - A novel method of analysis of double-lined eclipsing binaries containing a radially pulsating star is presented. The combined pulsating–eclipsing light curve is built up from a purely eclipsing light-curve grid created using an existing modelling tool. For every pulsation phase, the instantaneous radius and surface brightness are taken into account, being calculated from the disentangled radial velocity curve of the pulsating star and from its out-of-eclipse pulsational light curve and the light ratio of the components, respectively. The best model is found using the Markov chain Monte Carlo method. The method is applied to the eclipsing binary Cepheid OGLE-LMC-CEP-0227 (Ppuls = 3.80 d, Porb = 309 d). We analyse a set of new spectroscopic and photometric observations for this binary, simultaneously fitting OGLE V-band, I-band and Spitzer 3.6 μm photometry. We derive a set of fundamental parameters of the system significantly improving the precision comparing to the previous results obtained by our group. The Cepheid mass and radius are M1 = 4.165 ± 0.032 M⊙ and R1 = 34.92 ± 0.34 R⊙, respectively. For the first time a direct, geometrical and distance-independent determination of the Cepheid projection factor is presented. The value p = 1.21 ± 0.03(stat.) ± 0.04(syst.) is consistent with theoretical expectations for a short-period Cepheid and interferometric measurements for δ Cep. We also find a very high value of the optical limb darkening coefficients for the Cepheid component, in strong disagreement with theoretical predictions for static atmospheres at a given surface temperature and gravity.

AB - A novel method of analysis of double-lined eclipsing binaries containing a radially pulsating star is presented. The combined pulsating–eclipsing light curve is built up from a purely eclipsing light-curve grid created using an existing modelling tool. For every pulsation phase, the instantaneous radius and surface brightness are taken into account, being calculated from the disentangled radial velocity curve of the pulsating star and from its out-of-eclipse pulsational light curve and the light ratio of the components, respectively. The best model is found using the Markov chain Monte Carlo method. The method is applied to the eclipsing binary Cepheid OGLE-LMC-CEP-0227 (Ppuls = 3.80 d, Porb = 309 d). We analyse a set of new spectroscopic and photometric observations for this binary, simultaneously fitting OGLE V-band, I-band and Spitzer 3.6 μm photometry. We derive a set of fundamental parameters of the system significantly improving the precision comparing to the previous results obtained by our group. The Cepheid mass and radius are M1 = 4.165 ± 0.032 M⊙ and R1 = 34.92 ± 0.34 R⊙, respectively. For the first time a direct, geometrical and distance-independent determination of the Cepheid projection factor is presented. The value p = 1.21 ± 0.03(stat.) ± 0.04(syst.) is consistent with theoretical expectations for a short-period Cepheid and interferometric measurements for δ Cep. We also find a very high value of the optical limb darkening coefficients for the Cepheid component, in strong disagreement with theoretical predictions for static atmospheres at a given surface temperature and gravity.

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DO - 10.1093/mnras/stt1529

M3 - Article

VL - 436

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EP - 967

JO - Monthly Notices of the Royal Astronomical Society

JF - Monthly Notices of the Royal Astronomical Society

SN - 0035-8711

IS - 2

ER -