Pulsational Modeling and Projection Factor of RR Lyrae Stars

Boris Trahin, Pierre Kervella, Alexandre Gallenne, Antoine Mérand and Simon Borgniet

We present in this paper the application of the SPIPS algorithm (SpectroPhoto-Interferometry of Pulsating Stars) on the RR Lyrae prototype RR Lyr. SPIPS is a modeling tool that combines all the available observables (radial velocimetry, interferometry, and photometry) to estimate the physical parameters of the star (ratio distance/p-factor, effective temperature, presence of infrared excess, color excess, etc.). Using the known distance of the RR Lyr prototype as an input, we derive the value of its projection factor: p=1.34±0.07. The forthcoming Gaia DR2 will provide a considerable improvement in quantity and accuracy of the trigonometric parallaxes of variable stars. From this sample of RR Lyrae, the SPIPS modeling tool will enable a robust calibration of the distance scale.

Proceedings of the Polish Astronomical Society, vol. 6, 213-216 (2018)

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