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Astron. Astrophys. 352, 547-554 (1999)

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Pulsation models of [FORMULA] Scuti variables

II. [FORMULA] Scuti stars as precise distance indicators

J.O. Petersen 1 and J. Christensen-Dalsgaard 2

1 Astronomical Observatory, Niels Bohr Institute for Astronomy, Physics and Geophysics, Juliane Maries Vej 30, 2100 Copenhagen O, Denmark (oz@astro.ku.dk)
2 Theoretical Astrophysics Center, and Institute of Physics and Astronomy, Aarhus University, 8000 Aarhus C, Denmark (jcd@obs.aau.dk)

Received 25 June 1999 / Accepted 15 October 1999

Abstract

The Hipparcos period-luminosity relation for high-amplitude [FORMULA] Scuti stars is discussed as an average period-luminosity-colour-metallicity relation comparing the Hipparcos sample of calibrating stars with a more representative sample taken from McNamara (1997). The Hipparcos relation includes systematic effects of both colour and metallicity and agrees with other period-luminosity relations with an accuracy of about [FORMULA] mag.

Direct stellar-evolution and pulsation modelling is used to study effects on the average period-luminosity relation from the location of the high-amplitude variables within the instability strip given as a range in effective temperature (colour term) and the metallicity given as [Fe/H]. Using accurate data for the instability strip given by McNamara precise agreement with the Hipparcos relation is found. By fitting the bolometric magnitude as a function of pulsation period, effective temperature and metallicity an accuracy of 0.02-0.03 mag is obtained both within the narrow high-amplitude strip and including a much broader strip covering most of the full [FORMULA] Sct instability strip. Problems in practical application of this relation are briefly considered. Using [FORMULA] narrow-band photometry it seems possible to obtain this accuracy in determinations of distances to e.g. the Galactic Bulge and the Magellanic Clouds.

Key words: stars: distances – stars: fundamental parameters – stars: oscillations – stars: variables: ffi Sct

Send offprint requests to: J.O. Petersen (oz@astro.ku.dk)

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© European Southern Observatory (ESO) 1999

Online publication: December 2, 1999
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