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Astron. Astrophys. 362, 245-254 (2000)

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The [FORMULA] Scuti star [FORMULA] Tucanae

III. Observational guidelines for mode identification *

M. Paparó 1 and C. Sterken **  2

1 Konkoly Observatory, P.O. Box 67, 1525 Budapest XII, Hungary
2 University of Brussels (VUB), Pleinlaan 2, 1050 Brussels, Belgium

Received 29 March 2000 / Accepted 11 August 2000


On the basis of almost 2000 b, y photoelectric observations of [FORMULA] Tucanae collected in an international campaign at two sites and of almost 1500 v, u observations collected at one site, observational guidelines for mode identification have been searched. Not only the generally used plane ([FORMULA] versus [FORMULA] - [FORMULA]) but each combination of the nonadiabatic observables including amplitude ratio vs. amplitude ratio and phase difference vs. phase difference planes were checked for guidelines. Especially [FORMULA] amplitude ratio and [FORMULA] - [FORMULA] phase difference proved to be useful criteria for mode separation in the case of [FORMULA] Tucanae. The 10 pulsational frequency values published previously by Paparó et al. (1996) are distributed in three groups according to [FORMULA] and in two distinct levels according to [FORMULA] - [FORMULA]. The groups consist of closely spaced frequencies. Group III (15.86, 15.94 and 17.06 cycles/day) displays a higher, distinct level than the others according to the [FORMULA] amplitude ratio and unusual behaviour in u colour. Although the discriminative plane does not give the exact value of quantum numbers but predicts which theoretical modes must share the same behaviour. Calibration of the pure observational guidelines by new, delicate theoretical calculation for planes of nonadiabatic observables concerning the location of theoretical modes is urged.

Key words: stars: individual: Tuc = HR 139 – stars: oscillations – stars: variables: ffi Sct – stars: variables: general – stars: binaries: spectroscopic

* Based on observations obtained at the South African Astronomical Observatory, Sutherland, South Africa and at the European Southern Observatory, La Silla, Chile (Program 51 - 7 - 038)
** Research Director, Belgian Fund for Scientific Research (FWO)

Send offprint requests to: M. Paparó (paparo@ogyalla.konkoly.hu)

© European Southern Observatory (ESO) 2000

Online publication: October 30, 19100