### Abstract

We use B and V data of globular cluster variables to derive a formula for the distance moduli of RRab stars. The method employs the Fourier decomposition of the V light curve and the average B - V colour index. By using our former result for the V_{0} absolute magnitude, we also obtain an expression for the dereddened colour index. With the aid of the new formulae, the relative distance moduli can be estimated within an error of < 0.03 mag. Although we also make an absolute calibration, it is cautioned that this may be more affected by possible systematic errors originating mostly from the Baade-Wesselink magnitudes. On the basis of the scatter of the individual distance moduli computed with and without reddening correction, it is shown that inhomogeneous reddening plays a role in several clusters. By using our formulae we derive new expressions for the I_{c} and K absolute magnitudes on a sample of stars which contains mostly field stars with accurate photometry. As a by-product of this derivation we also give optimum estimations for the selective absorption coefficient R_{V}. We show that the K absolute magnitude contains important contribution also from the Fourier parameters, besides the well known dependence on the period. The I_{c} absolute magnitude is superbly correlated with the Fourier parameters, which implies that this colour is a very good candidate for the accurate estimation of the absolute magnitude.

Original language | English |
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Pages (from-to) | 218-228 |

Number of pages | 11 |

Journal | Astronomy and Astrophysics |

Volume | 322 |

Issue number | 1 |

Publication status | Published - Jun 1 1997 |

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### Keywords

- Globular clusters: general
- Stars: distances
- Stars: horizontal-branch
- Stars: oscillations
- Stars: variables

### ASJC Scopus subject areas

- Astronomy and Astrophysics
- Space and Planetary Science

### Cite this

*Astronomy and Astrophysics*,

*322*(1), 218-228.