The CoRoT star ID 100866999: a hybrid γ Doradus-δ Scuti star in an eclipsing binary system^⋆,⋆⋆

¹ Laboratoire Lagrange, UMR 7293, Université de Nice Sophia-Antipolis, CNRS, Observatoire de la Côte d’Azur, 06300 Nice, France
² Université de Toulouse, UPS-OMP, IRAP, 65000, Tarbes, France
e-mail: Philippe.Mathias@irap.omp.eu
³ CNRS, IRAP, 57 avenue d’Azereix, BP 826, 65008 Tarbes, France

Received: 16 May 2013
Accepted: 18 June 2013

Abstract

Context. The presence of g- and p-modes allows testing stellar models from the core to the envelope. Moreover, binarity in an eclipsing system constrains the physical parameters of the pulsating star.

Aims. CoRot ID 100866999 is a relatively large-amplitude hybrid γ Doradus-δ Scuti star with two clearly distinct frequency domains. The large number of detected frequencies allows a detailed study of the interaction between them. In addition, we can derive the fundamental parameters of both components from the study of the eclipsing light curve.

Methods. After removing the eclipsing phases, we analyzed the data with the Period04 package up to a signal-to-noise ratio S/N = 4. The light curve was then prewhitened with these oscillation frequencies to derive the fundamental parameters of the two components.

Results. The eclipsing light curve analysis results in a (1.8+1.1) M_⊙ system, both components being main sequence stars. We detect 124 frequencies related to luminosity variations of the primary. They are present in two well-separated domains: 89 frequencies in the interval [0.30;3.64] d^-1 and 35 in the interval [14.57; 33.96] d^-1. There are 22 γ Doradus frequencies separated by a constant period interval ΔP = 0.03493 d. These frequencies correspond to a series of g-modes of degree ℓ = 1 with successive radial orders k. We identify 21 linear combinations between the first nine γ Doradus frequencies. The δ Scuti domain is dominated by a large-amplitude frequency F = 16.9803 d^-1. The eight first γ Doradus frequencies f_i are present with much lower amplitude in the δ Scuti domain as F ± f_i. These interactions between g- and p-modes confirm the phenomenon we detected in another CoRoT star. The amplitude and the phase of the main frequency F shows a double-wave modulation along the orbital phase, giving rise to series of combination frequencies. Such combination frequencies are also detected, with lower amplitude, for the first γ Doradus modes.