A spectro-interferometric view of ℓ Carinae's modulated pulsations. Issue Volume 11:Issue A29B(2015) (27th October 2016)

• Record Type: Journal Article
• Authors: Anderson, Richard I.; Mérand, Antoine; Kervella, Pierre; Breitfelder, Joanne; Eyer, Laurent; Gallenne, Alexandre
• Editors: Benvenuti, Piero
• Is Part Of: Proceedings of the International Astronomical Union. Volume 11:Issue A29B(2015)
• Page Start: 501
• Page End: 504
• Publication Date: 2016-10-27
• Subjects: stars: oscillations, -- Cepheids, -- stars: distances, -- techniques: radial velocities, -- techniques: interferometric; Astronomy -- Congresses; Astronomy -- Periodicals; 520
• DOI: 10.1017/S1743921316005986
• Languages: English
• ISSNs: 1743-9213

Abstract

Abstract: 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.