Revisiting the fundamental properties of Cepheid Polaris using detailed stellar evolution models

Abstract

Polaris the Cepheid has been observed for centuries, presenting surprises and changing our view of Cepheids and stellar astrophysics, in general. Specifically, understanding Polaris helps anchor the Cepheid Leavitt law, but the distance must be measured precisely. The recent debate regarding the distance to Polaris has raised questions about its role in calibrating the Leavitt law and even its evolutionary status. In this work, I present new stellar evolution models of Cepheids to compare with previously measured CNO abundances, period change and angular diameter. Based on the comparison, I show that Polaris cannot be evolving along the first crossing of the Cepheid instability strip and cannot have evolved from a rapidly-rotating main sequence star. As such, Polaris must also be at least 118 pc away and pulsates in the first overtone, disagreeing with the recent results of Turner et al. (2013).

6 pages, 5 figures, resubmitted to A&A after minor revisions

References in corpus (6)

• Pre-Supernova Evolution of Massive Single and Binary Stars
• Direct Detection of the Close Companion of Polaris with the Hubble Space Telescope
• The VLT-FLAMES survey of massive stars: rotation and nitrogen enrichment as the key to understanding massive star evolution
• Cepheid Parallaxes and the Hubble Constant
• Extended envelopes around Galactic Cepheids III. Y Oph and alpha Per from near-infrared interferometry with CHARA/FLUOR
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Cited by in corpus (11)

• Hubble Space Telescope Trigonometric Parallax of Polaris B, Companion of the Nearest Cepheid
• The occurrence of classical Cepheids in binary systems
• Evolutionary status of Polaris
• Asteroseismology of the Double-Mode High-Amplitude $\delta$ Scuti Star VX Hydrae
• Homing in on Polaris: A 7 M${}_{\odot }$ first-overtone Cepheid entering the instability strip for the first time
• The Secret Lives of Cepheids: Evolution, Mass Loss, and Ultraviolet Emission of the Long-Period Classical Cepheid $l$ Carinae
• The strange evolution of the Large Magellanic Cloud Cepheid OGLE-LMC-CEP1812
• The Orbit of the Close Companion of Polaris: Hubble Space Telescope Imaging 2007 to 2014
• Evolving pulsation of the slowly rotating magnetic $\beta$ Cep star ${\xi }^1$ CMa
• Precise Fourier parameters of Cepheid Radial Velocity Curves
• Pulsation Period Change & Classical Cepheids: Probing the Details of Stellar Evolution