Related papers: Rotation and the Cepheid Mass Discrepancy
The equation of state (EOS) of high-density matter is still not clear and several recent observations indicate restrictions to EOSs. Theoretical studies should thus elucidate EOSs at high density and/or high temperature. Many theoretical…
We discuss the impact of possible differences in the slope of the Cepheid Period-Luminosity relation on the determination of extragalactic distances in the context of recent studies that suggest changes in this slope. We show that the…
The rotation rate of a star has important implications for the detectability, characterisation and stability of any planets that may be orbiting it. This chapter gives a brief overview of stellar rotation before describing the methods used…
We have computed stellar evolutionary models for stars in a mass range characteristic of Cepheid variables ($3<m/\Msol<12$) for different metallicities representative of the Galaxy and the Magellanic Clouds populations. The stellar…
Significant progress has been made during the last 10 years toward resolving the debate over the expansion rate of the Universe. The current value of the Hubble parameter, Ho, is now arguably known with an accuracy of 10%, largely due to…
We present the results of non-linear pulsation modeling of bump Cepheids in the LMC and SMC. By obtaining an optimal fit to the observed MACHO V and R lightcurves we can determine the fundamental parameters of each Cepheid, namely mass,…
Uncertainty in the metal abundance dependence of the Cepheid variable period- luminosity (PL) relation remains one of the outstanding sources of systematic error in the extragalactic distance scale and Hubble constant. To test for such a…
Mass loss and axial rotation are playing key roles in shaping the evolution of massive stars. They affect the tracks in the HR diagram, the lifetimes, the surface abundances, the hardness of the radiation field, the chemical yields, the…
The coincidence problem of late cosmic acceleration constitutes a serious riddle with regard to our understanding of the evolution of the Universe. Here we argue that this problem may someday be solved -or better understood- by expressing…
Rotation appears as a dominant effect in massive star evolution. It largely affects all the model outputs: inner structure, tracks, lifetimes, isochrones, surface compositions, blue to red supergiant ratios, etc. At lower metallicities, the…
Cepheid masses continue to be important tests of evolutionary tracks for intermediate mass stars as well as important predictors of their future fate. For systems where the secondary is a B star, {\it Hubble Space Telescope} ultraviolet…
We use theoretical Period-Luminosity and Period-Luminosity-Color relations in the VI passbands, as based on nonlinear, nonlocal and time-dependent convective pulsating models, to predict the reddening and true distance modulus of distant…
Many recent observations give restrictions to the equation of state (EOS) for high-density matter. Theoretical studies are needed to try to elucidate these EOSs at high density and/or temperature. With the many known rapidly rotating…
The 30 year orbit of the Cepheid Polaris has been followed with observations by the CHARA Array (Center for High Angular Resolution Astronomy) from 2016 through 2021. An additional measurement has been made with speckle interferometry at…
A curious rotation period distribution in the Color-Magnitude-Period Diagram (CMPD) of the Kepler field was recently revealed, thanks to data from Gaia and Kepler spacecraft. It was found that redder and brighter stars are spinning slower…
Cepheids have been the cornerstone of the extragalactic distance scale for a century. With high-quality data, these luminous supergiants exhibit a small dispersion in their Leavitt (period-luminosity) relation, particularly at longer…
The impact of rotation on the properties of low-mass stars at different evolutionary stages is first described by discussing the properties of stellar models computed with shellular rotation. The observational constraints that are currently…
Cepheid masses are particularly necessary to help solving the mass discrepancy, while independent distance determinations provide crucial test of the period-luminosity relation and Gaia parallaxes. We used CHARA/MIRC to measure the…
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…
We present preliminary results of an observational campaign devoted at establishing the influence of chemical composition on the Cepheid Period-Luminosity relation. The data are in good agreement with theoretical predictions based on…