EDP Sciences
Free access
Volume 426, Number 2, November I 2004
Page(s) 641 - 650
Section Stellar structure and evolution
DOI http://dx.doi.org/10.1051/0004-6361:20041048

A&A 426, 641-650 (2004)
DOI: 10.1051/0004-6361:20041048

RR Lyrae variables in Galactic globular clusters

IV. Synthetic HB and RR Lyrae predictions
S. Cassisi1, M. Castellani2, F. Caputo2 and V. Castellani2, 3

1  INAF - Osservatorio Astronomico di Teramo, via Mentore Maggini, 64100 Teramo, Italy
    e-mail: cassisi@te.astro.it
2  INAF - Osservatorio Astronomico di Roma, via Frascati 33, 00040 Monte Porzio Catone, Italy
    e-mail: m.castellani@mporzio.astro.it; caputo@mporzio.astro.it; vittorio@mporzio.astro.it
3  INFN Sezione di Ferrara,via Paradiso 12, 44100 Ferrara, Italy

(Received 7 April 2004 / Accepted 27 June 2004)

We present theoretical predictions concerning horizontal branch stars in globular clusters, including RR Lyrae variables, as derived from synthetic procedures collating evolutionary and pulsational constraints. On this basis, we explore the predicted behavior of the pulsators as a function of the horizontal branch morphology and over the metallicity range Z= 0.0001 to 0.006, revealing an encouraging concordance with the observed distribution of fundamentalised periods with metallicity. Theoretical relations connecting periods to K magnitudes and BV or VI Wesenheit functions are presented, both appearing quite independent of the horizontal branch morphology only with $Z\ge$ 0.001. Predictions concerning the parameter  R are also discussed and compared under various assumptions about the horizontal branch reference luminosity level.

Key words: stars: variables: RR Lyrae -- stars: evolution -- stars: horizontal-branch

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© ESO 2004