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Astron. Astrophys. 351, 597-606 (1999)

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4. Determination of atmospheric parameters: standard approach

4.1. Effective temperature

A comprehensive comparative analysis of the different determinations of the [FORMULA] value for [FORMULA] Cep was given by Fry & Carney (1997). It was shown that the obtained values are in good agreement with the independent results of Fernley et al. (1989) based on the infrared flux method and Evans & Teays (1996) based on spectrophotometry.

In the present paper we slightly modified the [FORMULA] values for different phases. The new values differ from old estimates by no more than 100 K. To specify the temperature, we used standard condition where there is no dependence of the abundances derived from the individual [FORMULA] lines upon line excitation potentials (see sixth column of Table 1).

Kiss & Szatmáry (1998) obtained very accurate [FORMULA] -[FORMULA] calibration that was also used for [FORMULA] Cep photometric temperature determination. It is very important to note that applied photometrical data were obtained by Kiss (1998) at the same epoch when the spectroscopic observations were carried out. Our spectroscopic estimates of [FORMULA] appeared to be in good agreement with [FORMULA] determination based on Kiss & Szatmáry photometrical calibration ([FORMULA] [FORMULA] is less than 100 K - see Table 1).

4.2. Microturbulent velocity

In order to derive the microturbulent velocity [FORMULA], we used the standard method which implies that there should be no dependence of iron abundance obtained from the individual [FORMULA] lines upon their equivalent widths (see Fig. 3). Results of [FORMULA] determination for all the phases are presented in Table 1 (the mark "S" denotes standard approach).

[FIGURE] Fig. 3. Sp1: [FORMULA]=0.443. Standard approach: [FORMULA] is determined using [FORMULA] lines ([FORMULA]); for reference, the result for [FORMULA] lines is indicated by [FORMULA].

It should be noted that visible dependence between the iron abundance derived from the individual [FORMULA] lines and the corresponding equivalent widths appeared when the [FORMULA] parameter was changed by approximately [FORMULA] 0.2 km s-1 or greater.

Our mean [FORMULA] value found for [FORMULA] Cep from the seven spectra is exactly the same as determined by Fry & Carney (1997) within the quoted error.

4.3. Gravity

In the standard calculations we kept the condition of the [FORMULA]/[FORMULA] ionization balance for all the phases. It enabled us to determine the [FORMULA] value and its variation during the pulsational cycle. The amplitude of the [FORMULA] variation was surprisingly small (see Table 1, [FORMULA] with a mark "S").

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© European Southern Observatory (ESO) 1999

Online publication: November 3, 1999