Mode characterisation in δ Scuti stars^*

I. ρ Pup, GN And, V1208 Aql and AV Cet

¹ Institute for Physics and Astronomy, University of Aarhus, Universitetsparken, Bygn. 520, 8000 Aarhus C, Denmark
² Nordic Optical Telescope, Apartado 474, 38700 Santa Cruz de La Palma, Spain

Corresponding author: T. H. Dall, tdall@ifa.au.dk

Received: 1 May 2001
Accepted: 5 March 2002

Abstract

We present new spectroscopic observations of four bright δ Scuti pulsators. Line indices of the Balmer lines can be used to establish mode identifications using the ratio R between such line index amplitudes and photometric amplitudes. For the well known radial pulsator ρ Pup an absolute value of the amplitude ratio of the radial mode was found to , consistent with earlier values of reported for other δ Scuti stars. In GN And we recover the recently reported newly excited mode, while the former dominant mode was not recovered. We confirm that V1208 Aql is a non-radial pulsator, containing two modes of different degree. In V1208 Aql we report a previously unseen mode behavior: the phases of both modes are reversed between the core and wings of the Hβ line, suggesting the presence of more undetected modes. For AV Cet we find that the dominant mode is a previously undetected one. We suggest the undertaking of new photometric observations of ρ Pup, GN And, V1208 Aql and AV Cet to determine the frequencies and amplitudes of the pulsations.