Determination of the iron content of Cepheids from the shape of their light curves

Abstract

We present the study of the metallicity dependence of the Fourier amplitude ratios R 21 and R 31 for the light curves of short-period Galactic classical Cepheids in B, V, R C and I C bands. Based on the available photometric and spectroscopic data we determined the relations between the atmospheric iron abundance, [Fe/H], and the Fourier parameters. Using these relations we calculated the photometric [Fe/H] values of all program Cepheids with an average accuracy of ±0.15 dex. No spectroscopic iron abundance was known before for 14 of these stars. These empirical results provide an alternate method to determine the iron abundance of classical Cepheids too faint for spectroscopic observations. We also checked whether the metal-poor Cepheids of both Magellanic Clouds follow the same relationships, and a good agreement was found.

The VMC survey – XXV. The 3D structure of the Small Magellanic Cloud from Classical Cepheids

“…Hence, formally, our values agree with literatures' within ∼ 1σ. However, as already remarked above, we expected to overestimate the abundances by some 0.1 dex due to the lack of metal poor calibrators in Klagyivik et al (2013)'s work, therefore the slight discrepancy observed is real.…”

“…with an rms=0.015 mag (Ripepi et al in preparation). Finally, the relations showed in Table 3 of Klagyivik et al (2013) Fig. 3 of 2013).…”

On the fine structure of the Cepheid metallicity gradient in the Galactic thin disk

“…During the last few years the dependence of the luminosity amplitude on metallicity has been investigated both from the theoretical point of view (Bono et al 2000b) and the observational (Klagyivik & Szabados 2009;Pedicelli et al 2010;Klagyivik et al 2013). In particular, Szabados & Klagyivik (2012), by using a large sample (327) of Galactic Cepheids with accurate pulsation parameters and spectroscopic metal abundances, found evidence that the luminosity and the radial velocity amplitudes slightly decrease with increasing iron abundance.…”

“…However, no firm conclusion has been reached since Pedicelli et al (2010), by using a similar data set, did not find a clear dependence on metallicity. More recently, Klagyivik et al (2013) by using short-period (log P ≤ 1.02) Cepheids found that the R 21 and the R 31 Fourier amplitude ratios decrease for increasing iron abundance.…”

A fémtartalom szerepe a csillagpulzációban

“…A Magellán-felhőkben levő csillagok [Fe/H] értékeit az általunk meghatározott fémesség-periódusarány összefüggésből becsültük meg. Megerősíthetjük, hogy a fémesség a legerősebb összefüggést a fénygörbe amplitúdójával és az első és a második harmonikus amplitúdóarányával (R 21 ) mutat, hasonlóan a klasszikus cefeidákhoz (Klagyivik et al, 2013). Azt is megmutattuk, hogy a fémesség kevésbé korrelál a φ 31 paraméterrel, szemben az RR Lyrae típusú változókkal.…”