Related papers: Rotation and the Cepheid Mass Discrepancy
The classical Cepheid $l$ Carinae is an essential calibrator of the Cepheid Leavitt Law as a rare long-period Galactic Cepheid. Understanding the properties of this star will also constrain the physics and evolution of massive ($M \ge 8$…
We have used the Wide Field and Planetary Camera 2 on board the Hubble Space Telescope to obtain V and I images of seven nearby galaxies. For each, we have measured a distance using the tip of the red giant branch (TRGB) method. By…
Helium-burning stars, in particular Cepheids, are especially difficult to model, as the choice of free parameters can greatly impact the shape of the blue loops - the part of the evolutionary track at which instability strip is crossed.…
We present here the final results of the Hubble Space Telescope Key Project to measure the Hubble constant. We summarize our method, the results and the uncertainties, tabulate our revised distances, and give the implications of these…
Considerable progress has been made in determining the Hubble constant over the past two decades. We discuss the cosmological context and importance of an accurate measurement of the Hubble constant, and focus on six high-precision…
Factors contributing to the scatter around the ridge-line period-luminosity relationship are listed, followed by a discussion how to eliminate the adverse effects of these factors (mode of pulsation, crossing number, temperature range,…
This is the second of two papers exploring the effects of metallicity on the multi-wavelength properties of Cepheids in terms of their multi-wavelength period-luminosity (PL) relations, impacting their use as extragalactic distance…
Thanks to HST, there are now many galaxies with Cepheid distances and these provide the main platform for the calibration of the secondary distance indicators. I review recent progress in our understanding of the standard candle properties…
Determining the expansion of the universe, i.e. the Hubble constant (H0) to better than 2% is required in order to understand the nature of dark energy. However, the two most accurate methods to do it, the cosmic microwave background and…
Present day estimates of the Hubble constant based on Cepheids and on the cosmic microwave background radiation are uncertain by roughly 10% (on the conservative assumption that the universe may not be PERFECTLY flat). Gravitational lens…
This paper uses an inductive method to investigate the factors responsible for variations in planetary-rotation periods. I began by showing the presence of a correlation between the masses of planets and their rotation periods. Then I…
Homogeneous multi-wavelength observations of classical Cepheids from the forthcoming Rubin-LSST have the potential to significantly contribute to our understanding of the evolutionary and pulsation properties of these pulsating stars.…
The theoretical period-luminosity relation for Cepheids was deduced from stellar evolution and pulsation computations. Questions concerning the metallicity dependence of the relation as well as the constancy of the pulsation `constant' Q in…
Physical parameters were recently measured for several Cepheids in eclipsing binary systems in the LMC. It is a good opportunity to compare these results with models obtained from pulsation theory. Having well determined physical parameters…
A large luminosity--linewidth template sample is now available, improved absorption corrections have been derived, and there are a statistically significant number of galaxies with well determined distances to supply the zero point. A…
An analysis of the observed characteristics of the Galactic Cepheid variables is carried out in the framework of their period-luminosity relation being used as a standard candle for distance measurement. The variation of the observed number…
The Galaxy rotation curve is usually assumed to be flat. However, some galaxies have rotation curves that are lower than the flat rotation curve. In our Galaxy the Keplerian rotation of interstellar clouds in the galactic longitude l=135…
Masses of classical Cepheids of 3 to 11 M$\odot$ are predicted by theory but those measured, clump between 3.6 and 5 M$\odot$. As a result, their mass-luminosity relation is poorly constrained, impeding our understanding of basic stellar…
Analyses of recent observations of the sole classical Cepheid in the Kepler field, V1154 Cygni, found random changes of about 30 minutes in the pulsation period. These period changes challenge standard theories of pulsation and evolution…
The correlation between the luminosities and rotation velocities of galaxies can be used to estimate distances to late-type galaxies. It is an appropriate moment to re-evaluate this method given the great deal of new information available.…