Lampens, P. ; Strigachev, A. ; Kim, S.-L. ; Rodríguez, E. ; López-González, M. J. ; Vidal-Saínz, J. ; Mkrtichian, D. ; Koo, J.-R. ; Kang, Y. B. ; van Cauteren, P. ; Wils, P. ; Kraicheva, Z. ; Dimitrov, D. ; Southworth, J. ; García Melendo, E. ; Gómez Forellad, J. M.

published in Astronomy and Astrophysics, 534, pp. A111 (2011)

Abstract: We present the results of a multi-site photometric campaign carried out in 2004-2008 for the Algol-type eclipsing binary system CT Her, the primary component of which displays δ Scuti-type oscillations. Our data consist of differential light curves collected in the filters B and V, which were analysed using the method of Wilson-Devinney (Phoebe). After identifying an adequate binary model and removing the best-fit light-curve solution, we performed a Fourier analysis of the residual B and V light curves to investigate the pulsational behaviour. We confirm the presence of rapid pulsations with a main period of 27.2 min. Up to eight significant frequencies with semi-amplitudes in the range 3 to 1 mmag were detected, all of which lie in the frequency range 43.5-53.5 d-1. This result is independent of the choice of the primary's effective temperature (8200 or 8700 K) since the light-curve models of the binary are very similar in both cases. This is yet another case of a complex frequency spectrum observed for an accreting δ Scuti-type star (after Y Cam). In addition, we demonstrate that the amplitudes of several pulsation frequencies provide evidence of variability on timescales as short as 1-2 years, perhaps even less. Moreover, our analysis takes into account some recently acquired spectra, from which we obtained the corresponding radial velocities for the years 2007-2009. Investigation of the O-C diagram shows that further monitoring of the epochs of eclipse minima of CT Her will cast new light on the evolution of its orbital period. Based on photometric data collected at the observatories listed in Table 1 and spectra acquired at the NAO, Bulgaria, and Calar Alto Observatory, Spain. The Skinakas Observatory is a collaborative project of the University of Crete, the Foundation for Research and Technology - Hellas, and the Max-Planck-Institut für Extraterrestrische Physik.Full Tables 3, 4, 9 and 12 are only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/534/A111

DOI: 10.1051/0004-6361/201117021
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