A photometric study of the light variations of the triple system DG Leo

¹ Koninklijke Sterrenwacht van België, Ringlaan 3, 1180 Brussel, Belgium e-mail: patricia.lampens@oma.be
² Instituto de Astrofísica de Andalucía, CSIC, Camino Bajo de Huetor, 18008 Granada, Spain
³ Instituto de Astronomía, UNAM Apartado Postal 70-264 México 04510, DF, Mexico
⁴ Beersel Hills Observatory, Laarheidestraat 166, 1650 Beersel, Belgium
⁵ Institute of Astronomy, KULeuven Celestijnenlaan 200B, 3001 Leuven, Belgium
⁶ Department of Physics and Astronomy, Aarhus University, 8000 Aarhus C., Denmark
⁷ Facultad de Física, Universidad Veracruzana, Veracruz, Mexico

Received: 8 November 2004
Accepted: 14 November 2005

Abstract

Multi-site and multi-year differential photometry of the triple star DG Leo reveals a complex frequency spectrum that can be modelled as the combination of at least three δ Scuti type frequencies in the range 11.5–13 c/d (with semi-amplitudes of 2–7 mmag) and a superimposed slow variability of larger amplitude. The period of the slow variation fits very well with half the orbital period of the inner spectroscopic binary indicating the presence of ellipsoidal variations caused by the tidally deformed components in a close configuration. These findings, together with the results of a recent spectroscopic analysis (showing that the system consists of a pair of mild Am stars and one A-type component of normal solar composition), infer that DG Leo is an extremely interesting asteroseismic target. Identification of which component(s) of this multiple system is (or are) pulsating and determination of the excited pulsation modes will both contribute to a much better understanding of the non-trivial link between multiplicity, chemical composition, rotation, and pulsation in the lower part of the classical Cepheid instability strip.