CoRoT 105906206: a short-period and totally eclipsing binary with a δ Scuti type pulsator^⋆,⋆⋆

¹ INAF – Osservatorio Astronomico di Roma, via Frascati 33, 00040 Monte Porzio Catone, Italy
e-mail: ronaldo.dasilva@oa-roma.inaf.it
² INAF – Osservatorio Astrofisico di Catania, via S. Sofia 78, 95123 Catania, Italy
³ Research and Scientific Support Department, ESA/ESTEC, PO Box 299, 2200 AG Noordwijk, The Netherlands
⁴ Thüringer Landessternwarte Tautenburg, Sternwarte 5, 07778 Tautenburg, Germany

Received: 25 October 2013
Accepted: 19 March 2014

Abstract

Aims. Eclipsing binary systems with pulsating components allow determination of several physical parameters of the stars, such as mass and radius, that can be used to constrain the modeling of stellar interiors and evolution when combined with the pulsation properties. We present the results of the study of CoRoT 105906206, an eclipsing binary system with a pulsating component located in the CoRoT LRc02 field.

Methods. The analysis of the CoRoT light curve was complemented by high-resolution spectra from the Sandiford at McDonald Observatory and FEROS at ESO spectrographs, which revealed a double-lined spectroscopic binary. We used an iterative procedure to separate the pulsation-induced photometric variations from the eclipse signals. First, a Fourier analysis was used to identify the significant frequencies and amplitudes due to pulsations. Second, after removing the contribution of the pulsations from the light curve we applied the PIKAIA genetic-algorithm approach to derive the best parameters for describing the system orbital properties.

Results. The light curve cleaned for pulsations contains the partial eclipse of the primary and the total eclipse of the secondary. The system has an orbital period of about 3.694 days and is formed by a primary star with mass M₁ = 2.25 ± 0.04 M_⊙, radius R₁ = 4.24±0.02 R_⊙, and effective temperature T_eff,1 = 6750 ± 150 K, and a secondary with M₂ = 1.29 ± 0.03 M_⊙, R₂ = 1.34±0.01 R_⊙, and T_eff,2 = 6152 ± 162 K. The best solution for the parameters was obtained by taking into account the asymmetric modulation observed in the light curve, known as the O’Connell effect, presumably caused by Doppler beaming. The analysis of the Fourier spectrum revealed that the primary component has p-mode pulsations in the range 5–13 d^-1, which are typical of δ Scuti type stars.