Modelling RR Lyrae pulsation: mission (im)possible?

Abstract

In order to make an in‐depth comparison between theory and observations, we analyse the light and velocity curves of various hydrodynamical models simulating RRab stars. The observations are represented by empirical formulae, derived in this and our earlier papers. It is shown that the overwhelming majority of the models tested do not follow the empirical relations regarding the shape of the light curves and the physical parameters. In almost all cases the luminosities predicted from the model light curves are significantly lower than the corresponding model values. The overall discrepancy of the models is an important indication of the limitation of the applicability of the present theoretical light and velocity curves in the determination of the physical parameters of these stars. In transforming the theoretical data to the observed light curves in V colour and in computing the observed radial velocities, it is shown that both bolometric correction and tracing the line‐forming regions have considerable effects on the evaluation of the observed quantities. In an effort to resolve the discrepancy between theory and observations, it is suggested that a proper evaluation of the bolometric correction and radial velocity based on complete dynamical atmosphere models may be a useful step in this direction.

The Variable Stars of the Draco Dwarf Spheroidal Galaxy: Revisited

“…This deviation parameter is determined from a comparison of the observed and predicted Fourier parameters. An updated version of this test is provided in Kovacs & Kanbur (1998). In order for a star to be a good candidate for the Jurcsik & Kovacs method, the D M parameter criterion must be met.…”

Toward a Better Understanding of the Distance Scale From Rr Lyrae Variable Stars: A Case Study for the Inner Halo Globular Cluster NGC 6723

“…(see, for example, Simon & Lee 1981;Jurcsik 1998;Kovács & Kanbur 1998;Kovács & Walker 1999Kovács & Kupi 2007). The practical application of Fourier parameters to characterize the RRLs in our Galaxy or in the Large Magellanic Cloud (LMC) appears to be successful, but some worrisome signs have started to emerge lately.…”

Blazhko stars: Always distorted?

“…A compatibility criterion (D m ) of the light curves with those of a large sample of RRab stars was given in Kovács & Kanbur (1998, see also Jurcsik & Kovács 1996. This method utilizes the interrelations between the Fourier parameters of the light curve and serves as a firmer restriction on the actual values of the Fourier parameters than their possible ranges.…”

“…In this paper we reexamine the light change variations of Blazhko stars utilizing the A V -A v rad relation, compare the measured and calculated [Fe/H] values (Jurcsik & Kovács 1996) at different Blazhko phases, and measure the compatibility of the light curves with that of normal RRab stars using the interrelations between the Fourier parameters (Kovács & Kanbur 1998) Liu (1991) provides the opportunity and also makes it necessary to refine the positions of Blazhko variables on this diagram. In order to do so, the literature was searched for radial velocity measurements of known Blazhko variables.…”