Toward a renewed Galactic Cepheid distance scale from Gaia and optical interferometry
1 Unidad Mixta Internacional Franco-Chilena de Astronomía (CNRS UMI 3386), Departamento de Astronomía, Universidad de Chile, Las Condes, Chile
2 LESIA (CNRS UMR 8109), Observatoire de Paris, PSL, CNRS, UPMC, Univ. Paris-Diderot, France
3 European Southern Observatory, Alonso de Córdova 3107, Casilla 19001, Santiago 19, Chile
4 Laboratoire Lagrange, UMR 7293, Univ. de Nice Sophia-Antipolis, CNRS, Obs. de la Côte d’Azur, France
5 Physics and Astronomy Department, The Johns Hopkins University, Baltimore, MD 21218, USA
6 Konkoly Observatory, MTA CSFK, Konkoly Thege M. út 15-17, H-1121, Hungary
7 Department of Astronomy & Astrophysics, Pennsylvania State University, University Park, PA 16802, USA
8 Universidad de Concepción, Departamento de Astronomía, Casilla 160-C, Concepción, Chile
9 Nicolaus Copernicus Astronomical Center, Polish Academy of Sciences, Warszawa, Poland
Published online: 8 September 2017
Through an innovative combination of multiple observing techniques and modeling, we are assembling a comprehensive understanding of the pulsation and close environment of Cepheids. We developed the SPIPS modeling tool that combines all observables (radial velocimetry, photometry, angular diameters from interferometry) to derive the relevant physical parameters of the star (effective temperature, infrared excess, reddening, …) and the ratio of the distance and the projection factor d/p. We present the application of SPIPS to the long-period Cepheid RS Pup, for which we derive p = 1.25±0.06. The addition of this massive Cepheid consolidates the existing sample of p-factor measurements towards long-period pulsators. This allows us to conclude that p is constant or mildly variable around p = 1.29±0.04 (±3%) as a function of the pulsation period. The forthcoming Gaia DR2 will provide a considerable improvement in quantity and accuracy of the trigonometric parallaxes of Cepheids. From this sample, the SPIPS modeling tool will enable a robust calibration of the Cepheid distance scale.
© The Authors, published by EDP Sciences, 2017
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