Physical parameter determination of seven RR Lyrae stars in Bootes

Rr Lyrae Stars in the Macho Database

The MACHO Project has catalogued 8000 RR Lyrae stars in the Large Magellanic Cloud, 1800 in the Galactic bulge, and 50 in the Sgr dwarf galaxy. These variables are excellent distance indicators, and are used as tools to study the structure of the Large Magellanic Cloud and the bulge. The large datasets also probe uncommon pulsation modes. A number of double-mode RR Lyrae stars (RRd) are found i...

Irregularities in atmospheric pulsations of RR Lyrae stars

From high spectral resolution observations of the Fe II line at 4923.921Å, it is shown that the star RR Lyrae shows significant differences, both in radial velocity and in line FWHM, from one pulsation cycle to the next. Two explanations are discussed. The first one is the multiperiodic character of the pulsation (Blazhko effect) which was recently detected (Chadid et al. 1999). In this case, t...

Multi-Periodic Oscillations in Cepheids and RR Lyrae-Type Stars

Classical Cepheids and RR Lyrae-type stars are usually considered to be textbook examples of purely radial, strictly periodic pulsators. Not all the variables, however, conform to this simple picture. In this review I discuss different forms of multi-periodicity observed in Cepheids and RR Lyrae stars, including Blazhko effect and various types of radial and nonradial multi-mode oscillations.

Are the Luminosities of Rr Lyrae Stars Affected by Second Parameter Effects?

Predicted and Empirical Radii of Rr Lyrae Stars

We present new theoretical Period-Radius-Metallicity (PRZ) relations for RR Lyrae stars. Current predictions are based on a large set of nonlinear, convective models that cover a broad range of chemical abundances and input parameters. We also provide new and homogeneous estimates of angular diameters for a sample of field RR Lyrae stars using a recent calibration of the Barnes-Evans surface br...