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arXiv · 1003.4445

Fundamental parameters of RR Lyrae stars from multicolour photometry and Kurucz atmospheric models. I. Theory and practical implementation

Szabolcs Barcza
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Abstract

A photometric calibration of Kurucz static model atmospheres is used to obtain parameters of RR Lyrae stars: variation of stellar angular radius $\vartheta$, effective temperature $T_{\rm e}$, and gravity $g_{\rm e}$ as a function of phase, interstellar reddening $E(B-V)$ toward the star, and atmospheric metallicity $M$. Photometric and hydrodynamic conditions are given to find the phases of pulsation when the quasi-static atmosphere approximation (QSAA) can be applied. The QSAA is generalized to a non-uniformly moving spherical atmosphere, and the distance $d$, mass ${\cal M}$, and atmospheric motion are derived from the laws of mass and momentum conservation. To demonstrate the efficiency of the method, the $UBV(RI)_C$ photometry of SU Dra was used to derive the following parameters: $[M]=-1.60\pm .10$ dex, $E(B-V)=0.015\pm .010$, $d=663\pm 67$ pc, ${\cal M}=(0.68\pm .03){\cal M}_\odot$, equilibrium luminosity, $L_{\rm eq}=45.9\pm 9.3L_\odot$, $T_{\rm eq}=6813\pm 20$ K.

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Szabolcs Barcza. 2010-03-23. Fundamental parameters of RR Lyrae stars from multicolour photometry and Kurucz atmospheric models. I. Theory and practical implementation. https://arxiv.org/abs/1003.4445

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