RR Lyrae pulsational temperature scales: on the consistency between different empirical relations |
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| Authors: | Renato De Santis |
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| Institution: | Osservatorio Astronomico di Collurania, Via M. Maggini, I-64100 Teramo, Italy |
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| Abstract: | In this paper, by assuming the equilibrium temperatures of RRab Lyrae variables defined by Carney, Storm & Jones as correct we show that temperatures derived from ( B ? V ) colour (mean colour over the pulsational cycle calculated on the magnitude scale) transformations by Bessel, Castelli & Plez are consistent with the Carney et al. equilibrium temperatures within a probable error of δ log T e =±0.003 . As a consequence, it is shown that the pulsational temperature scale temperature–period–blue amplitude T eff= f ( P , A B )] relation provided by De Santis, who studied the ( B ? V ) colour of about 70 stars of Lub's sample, is a suitable relation, being reddening- and metallicity-free, to calculate equilibrium temperatures for RRab variables. This relation is independent of variable mass and luminosity within a large range of period-shift from the mean period–amplitude relation valid for Lub's sample of variables. On the contrary, it is also shown that a temperature–amplitude–metallicity relation is strictly dependent on the period–amplitude relation of the sample used for calibrating it: we prove that this means it is dependent on both the mass and luminosity variations of variables. |
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| Keywords: | stars: evolution stars: interiors globular clusters: general |
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