A pulsational approach to near-infrared and visual magnitudes of RR Lyr stars

Abstract

In this paper, we present an improved theoretical scenario concerning near‐infrared and visual magnitudes of RR Lyr variables, as based on up‐to‐date pulsating models. New relations connecting V and K absolute magnitudes with periods, mass, luminosity and metal content are discussed separately for fundamental and first‐overtone pulsators. We also show that the V−K colours are predicted to supply tight constraints on the pulsator intrinsic luminosity. On this basis, we revisit the case of the prototype variable RR Lyr, showing that the parallax inferred by this new pulsational approach appears in close agreement with Hubble Space Telescope absolute parallax. Moreover, available K and V measurements for field and cluster RR Lyr variables with known reddening and metal content are used to derive a relation connecting the K absolute magnitude to period and metallicity (MK–[Fe/H]–log P) as well as a new calibration of the MV–[Fe/H] relation. The comparison between theoretical prescriptions and observations suggests that RR Lyr stars in the field and in galactic globular clusters (GGCs) should have quite similar evolutionary histories. The comparison between theory and observations also discloses a general agreement that supports the reliability of the current pulsational scenario. On the contrary, current empirical absolute magnitudes based on the Baade–Wesselink (BW) method suggest relations with a zero‐point which is fainter than is predicted by pulsation models, together with a milder metallicity dependence. However, preliminary results based on a new calibration of the BW method provided by Cacciari et al. (2000) for RR Cet and SW And appear in a much better agreement with the pulsational predictions.

Properties of RR Lyrae stars in the inner regions of the Large Magellanic Cloud

“…and both the metal-rich and metal-poor extremes are represented by only two stars. Although our results are very similar to those obtained by Bono et al (2003), Catelan et al (2004), and Sollima et al (2008), we cannot reach firm conclusions concerning the metallicity dependence of the period-luminosity relation in the J band based solely on these data. Therefore, to increase the sample size, we added the Sollima et al (2006a) dataset for ω Cen (Fig.…”

“…Accordingly, considerable attention has been devoted to this subject over the past several years, with several papers recently published on its accurate determination, by both empirical and theoretical approaches (e.g., Del Principe et al 2006;Solima et al 2006Solima et al , 2008Feast et al 2008;Pietrzyński et al 2008;Szewczyk et al 2008). From the theoretical point of view, its properties have been investigated by Bono et al (2001Bono et al ( , 2003, Cassisi et al (2004), and Catelan et al (2004).…”

Near-Infrared photometry of the LMC cluster Reticulum

“…For the K band we used the fundamental pulsators relation given by Bono et al (2003) M K = 0.568− 2.101 log P + 0.125 log Z …”

“…The luminosity of each pulsator can be evaluated using the (V − K) period-color relation (Bono et al, 2003) …”

“…They found that the relation shows only a mild dependence on the luminosity level and a small dependence on the mass. Moreover, Bono et al (2003) showed that the residual uncertainty on the luminosity level can be further reduced by using a period-colormetallicity relation. The theory has been tested by Bono et al (2002) on RR Lyrae itself, whose trigonometric parallax was recently measured by HST (Benedict et al, 2002).…”