The multiperiodicity of the γ Doradus stars HD 224945 and HD 224638 as detected from a multisite campaign^*

¹ Osservatorio Astronomico di Brera, Via Bianchi 46, 23807 Merate, Italy
² South African Astronomical Observatory, PO Box 9, Observatory 7935, Cape Town, South Africa
³ Instituto de Astrofisica de Andalucia, C.S.I.C., Apdo. 3004, 18080 Granada, Spain
⁴ Cerro Tololo Inter-American Observatory, Casilla 603, La Serena, Chile
⁵ Ege University, Science Faculty, Dept. of Astronomy and Space Sciences, Bornova 35100 Izmir, Turkey
⁶ Department of Physics and Astronomy, University of Hawaii - Hilo, 200 West Kawili Street, Hilo, Hawaii, 96720-4091, USA

Corresponding author: E. Poretti, poretti@merate.mi.astro.it

Received: 11 September 2001
Accepted: 9 January 2002

Abstract

We discuss new photometric data collected on the γ Dor variables HD 224945 and HD 224638. Multiperiodicity was detected in both stars, thanks to the clear spectral window of a multisite campaign that involved five observatories. HD 224945 shows the shortest period among the γ Dor stars, i.e., 0.3330 d. The pulsation behaviour is very different: HD 224945 displays a set of frequencies spread over an interval much larger than that of HD 224638. We clearly found evidence for amplitude variations in the excited modes by comparing data from different years. HD 224945 and HD 224638 are among the best examples of γ Dor stars that show multimode pulsations, which make them very interesting from an asteroseismological point of view.