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Astron. Astrophys. 325, 563-568 (1997)

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The [FORMULA]  Scuti star [FORMULA]  Tucanae *

II. uvby colour variations and pulsational/orbital properties

C. Sterken **

University of Brussels (VUB), Pleinlaan 2, B-1050 Brussels, Belgium

Received 5 February 1997 / Accepted 24 March 1997

Abstract

On the basis of almost 1500 uvby photometric observations of [FORMULA]  Tucanae collected in 1993, we discuss the colour variation of this multi-periodic [FORMULA]  Scuti star and debate some of its binary and pulsational properties. The frequencies [FORMULA] and [FORMULA] cd-1 embody orbital motion in a 7:d04 day ellipsoidal configuration characterised by a light curve with unequal maxima and minima and a colour index that becomes bluer during the minimum phases. The first results of an analysis of the light curve points towards a mass ratio q of the order of 0.10-0.15. We present dependable numerical values for colour phase differences and amplitude ratios [FORMULA] and [FORMULA] which can be used for pulsation-mode identification. The principal pulsation frequency [FORMULA] cd-1 is reconcilable with a radial mode.

Key words: stars: individual:  Tuc – stars: oscillations – stars: ffi Scuti stars – stars: binaries: general

* Based on observations obtained at the European Southern Observatory, La Silla, Chile (Program 51-7-038)
** Belgian Fund for Scientific Research (FWO)

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© European Southern Observatory (ESO) 1997

Online publication: April 28, 1998

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