NOAO >   Observing Info >   Approved Programs >   2018A-0055

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Program Information for 2018A-0055


PI: Alexandre Gallenne, ESO, agallenn@eso.org
Address: Science, Alonso de Cordova 3107, Santiago de Chile Chile

CoI: Pierre Kervella, Observatoire de Paris
CoI: Antoine Merand, ESO
CoI: Nancy Evans, Harvard-Smithsonian Center for Astrophysics
CoI: Charles Proffitt, STScI

Title: Multiplicity of Galactic Cepheids from long-baseline interferometry

Abstract: This proposal is a follow-up of our observing program on long- orbital period binary Cepheids. It also includes targets for which the detection need to be confirmed. The study of Cepheids in binary systems leads to a better understanding of the age and evolution of Cepheids. Our goal is to measure the astrometric position of the companions at additional epochs. For each epoch, we will accurately measure the angular separation, position angle and the flux ratio. All these observations will be then combined with accurate radial velocity measurements to estimate all the orbital elements, the dynamical mass, and the distance of the Cepheid systems. These observations are critical as we have obtained several cycles of HST/STIS for three Cepheids to measure the radial velocity (RV) of the companions, which will be later combined with these astrometric measurements. In addition, Gaia will soon provide accurate parallaxes of several binary Cepheids, which will be a major asset to our program as we will not necessarily need RVs of the companions to estimate the masses. Since the separations are $< 40$mas, we need interferometry. We therefore request to use MIRC in the H band, with the low spectral resolution.

Program Type: Standard/Galactic

Scheduled Nights:
Run 1 (2018A):  CHARA/MIRC -- 30hrs


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NOAO >   Observing Info >   Approved Programs >   2018A-0055

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