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A spectro-interferometric view of ℓ Carinae's modulated pulsations

Published online by Cambridge University Press:  27 October 2016

Richard I. Anderson ,
Antoine Mérand ,
Pierre Kervella ,
Joanne Breitfelder ,
Laurent Eyer  and
Alexandre Gallenne
Richard I. Anderson
Affiliation:
Dept. of Physics & Astronomy, The Johns Hopkins University, Baltimore, MD, USA email: [email protected]
Antoine Mérand
Affiliation:
European Southern Observatory, Santiago, Chile
Pierre Kervella
Affiliation:
LESIA (UMR 8109), Obs. de Paris, PSL, CNRS, UPMC, Univ. Paris-Diderot, France Unidad Mixta Internacional Franco-Chilena de Astronomía, CNRS/INSU, France(UMI 3386) and Depto. de Astronomía, Universidad de Chile, Las Condes, Santiago, Chile
Joanne Breitfelder
Affiliation:
European Southern Observatory, Santiago, Chile LESIA (UMR 8109), Obs. de Paris, PSL, CNRS, UPMC, Univ. Paris-Diderot, France
Laurent Eyer
Affiliation:
Dept. of Astronomy, University of Geneva, Switzerland
Alexandre Gallenne
Affiliation:
Universidad de Concepción, Departamento de Astronomía, Concepción, Chile
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Abstract

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Classical Cepheids are radially pulsating stars that enable important tests of stellar evolution and play a crucial role in the calibration of the local Hubble constant. ℓ Carinae is a particularly well-known distance calibrator, being the closest long-period (P ~ 35.5 d) Cepheid and subtending the largest angular diameter. We have carried out an unprecedented observing program to investigate whether recently discovered cycle-to-cycle changes (modulations) of ℓ Carinae's radial velocity (RV) variability are mirrored by its variability in angular size. To this end, we have secured a fully contemporaneous dataset of high-precision RVs and high-precision angular diameters. Here we provide a concise summary of our project and report preliminary results. We confirm the modulated nature of the RV variability and find tentative evidence of cycle-to-cycle differences in ℓ Car's maximal angular diameter. Our analysis is exploring the limits of state-of-the-art instrumentation and reveals additional complexity in the pulsations of Cepheids. If confirmed, our result suggests a previously unknown pulsation cycle dependence of projection factors required for determining Cepheid distances via the Baade-Wesselink technique.

Keywords

stars: oscillationsCepheidsstars: distancestechniques: radial velocitiestechniques: interferometric
Type
Contributed Papers
Information
Proceedings of the International Astronomical Union , Volume 11 , General Assembly A29B: Astronomy in Focus , August 2015 , pp. 501 - 504
Copyright
Copyright © International Astronomical Union 2016 

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