G
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Last name: GIEREN
First name: W.
International audience
Context. The Baade-Wesselink (BW) method, which combines linear and angular diameter variations, is the most common method to determine the distances to pulsating stars. However, the projection factor, p-factor, used to convert radial velocities into pulsation velocities, is still poorly calibrated. This parameter is critical on the use of this...
Context: The cross correlation method (hereafter CC) is widely used to derive the radial velocity curve of Cepheids when the signal to noise ratio of the spectra is low. However, if it is used with an inaccurate projection factor, it might introduce some biases in the Baade-Wesselink (BW) methods of determining the distance of Cepheids. In...
International audience
International audience
International audience
Aims. We aim to investigate the infrared excess of 45 Milky Way (MW) Cepheids combining different observables in order to constrain the presence of circumstellar envelopes (CSEs). Methods. We used the SpectroPhoto-Interferometry of Pulsating Stars (SPIPS) algorithm, a robust implementation of the parallaxof-pulsation method that combines...
International audience
International audience
Observations of 48 red-clump stars were obtained in the H band with the PIONIER instrument installed at the Very Large Telescope Interferometer. Limb-darkened angular diameters were measured by fitting radial intensity profile I(r) to square visibility measurements. Half the angular diameters determined have formal errors better than 1.2%,...
International audience
Context. Type II Cepheids are old pulsating stars that can be used to trace the distribution of an old stellar population and to measure distances to globular clusters and galaxies within several megaparsecs, and by extension, they can improve our understanding of the cosmic distance scale. One method that can be used to measure the distances...
International audience
International audience
International audience
Aims. Surface brightness – colour relations (SBCRs) are very useful tools for predicting the angular diameters of stars. They offer the possibility to calculate very precise spectrophotometric distances by the eclipsing binary method or the Baade-Wesselink method. Double-lined Detached Eclipsing Binary stars (SB2 DEBs) with precisely known...
International audience
Context. The Baade-Wesselink (BW) method of distance determination of Cepheids is used to calibrate the distance scale. Various versions of this method are mainly based on interferometry and/or the surface-brightness color relation (SBCR). Aims. We quantify the impact of the SBCR, its slope, and its zero point on the projection factor. This...
Our sample is made up of 64 Classical Galactic Cepheids with pulsation periods in the range 2 to 68 days. We provide the full details of our sample in Table A.1. We present both the six correlation templates built to derive tailored cross-correlation functions (CCFs), the CCFs themselves, and the derived radial velocity and line profile...
International audience
In the last 20 years, over the course of the Araucaria project, we have studied 20 very special eclipsing binary systems in the Large Magellanic Cloud (LMC). Based on these systems and our newly calibrated surface brightness-colour relation we have measured a distance to the LMC that is accurate to 1%. This is currently the best benchmark for...
Context. The infrared (IR) excess of classical Cepheids is seldom studied and poorly understood despite observational evidence and the potential for its contribution to induce systematics on the period-luminosity (PL) relation used in the calibration of the extragalactic distance scale. Aims: This study aims to understand the physical origin of...
International audience
Context. The projection factor p is the key quantity used in the Baade-Wesselink (BW) method for distance determination; it converts radial velocities into pulsation velocities. Several methods are used to determine p, such as geometrical and hydrodynamical models or the inverse BW approach when the distance is known. Aims. We analyze new...
International audience