Reddenings of FGK supergiants and classical Cepheids from spectroscopic data

Accurate and homogeneous atmospheric parameters (Teff, log (g), Vt, [Fe/H]) are derived for 74 FGK non-variable supergiants from high-resolution, high signal-to-noise ratio, echelle spectra. Extremely high precision for the inferred effective temperatures (10-40 K) is achieved by using the line-depth ratio method. The new data are combined with atmospheric values for 164 classical Cepheids, observed at 675 different pulsation phases, taken from our previously published studies. The derived values are correlated with unreddened B-V colours compiled from the literature for the investigated stars in order to obtain an empirical relationship of the form: (B-V)o = 57.984 - 10.3587(log Teff)^2 + 1.67572(log Teff)^3 - 3.356(log (g)) + 0.0321(Vt) + 0.2615[Fe/H] + 0.8833((log (g))(log Teff)). The expression is used to estimate colour excesses E(B-V) for individual supergiants and classical Cepheids, with a precision of +-0.05 mag. for supergiants and Cepheids with n=1-2 spectra, reaching +-0.025 mag. for Cepheids with n>2 spectra, matching uncertainties for the most sophisticated photometric techniques. The reddening scale is also a close match to the system of space reddenings for Cepheids. The application range is for spectral types F0--K0 and luminosity classes I and II.Comment: accepted for publication (MNRAS

THE ABUNDANCES OF THE ELEMENTS OF THE MAGELLANIC CLOUDS

The results of the spectroscopic researches of classical Chepheids of the Magellanic Clouds (MC) are presented in this paper. 21 spec tra for the Large Magellanic Cloud (LMC) and 10 for the Small Magellanic Cloud (SMC) were investigated. I obtained highly accurate values of effective temper atures (Teff ), of the logarithm of the surface gravity(log g), of the microturbulence velocity (Vt), of abun dances of elements for all of the objects. There is a good agreement with previous studies, some data were obtained for the first time

SPECTRAL LUMINOSITY INDICATORS FOR FGKSUPERGIANTS AND CLASSICAL CEPHEIDS

We have determined 28 relations between M ν, T eff and line depths ratios Rλ1/R λ2. These relations have been used for the estimation of the absolute magnitudes M ν of 56 FGK supergiants with an error 0.05-0.30 mag (Table 1). The application range is F0-K0, luminosity classes I and II

The study of galactic beat cepheids with application of its results to those in the Magellanic Clouds

A thorough study of the correlation between P1=P0 ratio, fundamental period, and chemical composition (abundances of metals that compose Z) was conducted to investigate the significance of the iron-peak elements on the ratio. The results suggested a more accurate P1=P0 ratio that can be useful as an alternative means of determining a beat Cepheid’s metallicity. Metallicities for a large sample of stars were analysed using the suggested ratio. The metallicity distribution function for the Magellanic Clouds projected on the celestial sphere was constructed for the first time, and several stars with anomalous metallicities were detected. The average metallicities of the Magellanic Clouds were also obtained independently: –0.30 dex for the Large Magellanic Cloud (LMC) and –0.49 dex for the Small Magellanic Cloud (SMC). The [Fe=H] values for two newly-found bimodal Cepheids in the Galactic bulge were estimated: –0.39 dex for OGLE-BLG-CEP-03 and –0.29 dex for OGLE-BLG-CEP-21.A thorough study of the correlation between P1=P0 ratio, fundamental period, and chemical composition (abundances of metals that compose Z) was conducted to investigate the significance of the iron-peak elements on the ratio. The results suggested a more accurate P1=P0 ratio that can be useful as an alternative means of determining a beat Cepheid’s metallicity. Metallicities for a large sample of stars were analysed using the suggested ratio. The metallicity distribution function for the Magellanic Clouds projected on the celestial sphere was constructed for the first time, and several stars with anomalous metallicities were detected. The average metallicities of the Magellanic Clouds were also obtained independently: –0.30 dex for the Large Magellanic Cloud (LMC) and –0.49 dex for the Small Magellanic Cloud (SMC). The [Fe=H] values for two newly-found bimodal Cepheids in the Galactic bulge were estimated: –0.39 dex for OGLE-BLG-CEP-03 and –0.29 dex for OGLE-BLG-CEP-21

INVESTIGATION OF DIFFUSE INTERSTELLAR BANDS OF ORGANIC MOLECULES IN THE SPECTRA OF CEPHEID STARS

We describe an effective method of investigation of the Diffuse Interstellar Bands (DIBs) in the spectra of Cepheid stars. DIBs are believed to originate from the absorption of such carriers as polycyclic aromatic hydrocarbons in the interstellar gaseous clouds located between an observer and the stars whose spectra were recorded. We performed a detailed consideration of the DIB at 6613 A in our sample of spectra for more than 250 stars. The quantitative characteristics of the DIB absorption features will be studied in connection with the interstellar absorption data, and after that, they will be used in the mapping of the Galactic disc.We describe an effective method of investigation of the Diffuse Interstellar Bands (DIBs) in the spectra of Cepheid stars. DIBs are believed to originate from the absorption of such carriers as polycyclic aromatic hydrocarbons in the interstellar gaseous clouds located between an observer and the stars whose spectra were recorded. We performed a detailed consideration of the DIB at 6613 A in our sample of spectra for more than 250 stars. The quantitative characteristics of the DIB absorption features will be studied in connection with the interstellar absorption data, and after that, they will be used in the mapping of the Galactic disc.We describe an effective method of investigation of the Diffuse Interstellar Bands (DIBs) in the spectra of Cepheid stars. DIBs are believed to originate from the absorption of such carriers as polycyclic aromatic hydrocarbons in the interstellar gaseous clouds located between an observer and the stars whose spectra were recorded. We performed a detailed consideration of the DIB at 6613 A in our sample of spectra for more than 250 stars. The quantitative characteristics of the DIB absorption features will be studied in connection with the interstellar absorption data, and after that, they will be used in the mapping of the Galactic disc

Accurate luminosities for F-G supergiants from FeII/FeI line depth ratios

International audienceLuminous FG supergiants can be used as extragalactic distance indicators. In order to fully exploit the properties of these bright stars, we must first learn how to measure their luminosities. Based primarily on classical Cepheids and supergiants in clusters and OB associations, we have derived 80 empirical relations connecting the line depth ratios of FeII/FeI lines with the absolute magnitudes Mv and the effective temperatures Teff. These relations have been applied to estimate the absolute magnitudes of 98 FG supergiants with an error of +/-0.26mag. The application range of our calibrations is spectral types F2-G8 and luminosity classes I and II (absolute magnitudes Mv, -0.5 to -8 mag). A comparison of our Mv determinations with values from the literature shows good agreement