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

• Published in: Proceedings of the International Astronomical Union Vol. 11; no. A29B; pp. 501 - 504
• Main Authors: Anderson, Richard I, Merand, Antoine, Kervella, Pierre, Breitfelder, Joanne, Eyer, Laurent, Gallenne, Alexandre, Benvenuti, Piero
• Format: Journal Article
• Language: English
• Published: Cambridge Cambridge University Press 01.08.2015
• Subjects: Angular velocity; Astronomy; Astrophysics; Calibration; Cepheid variables; Instrumentation; Interferometry; Modulation; Projection; Pulsation; Radial velocity; Spectrum analysis; Star & galaxy formation; Stars & galaxies
• ISSN: 1743-9213; 1743-9221
• DOI: 10.1017/S1743921316005986

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. 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 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 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.