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Astron. Astrophys. 329, 721-724 (1998)

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3. Results

In Figs. 1 and 2, we present dependencies on oscillator strengths and lower excitation potential for sensitivity indicators of central depths of iron lines to the temperature, the gas pressure, the microturbulent velocity. Figs. 3 and 4 give the average geometrical heights of localization of the effective response to the temperature variations for central depths and the equivalent widths of these lines. In addition, Figs. 3c, 4c show for central line depths the average formation heights in comparison with heights of effective responses to variations of the temperature, the gas pressure, and the microturbulent velocity. The heights of formation are computed from the contribution function to the line depression (Gurtovenko et al., 1991).


[FIGURE] Fig. 1. Indicators of the sensitivity of central depths of Fe I lines depending on the oscillator strengths [FORMULA] and lower excitation potentials (EP, eV): a to the temperature; b to the gas pressure; c to the microturbulent velocity.

[FIGURE] Fig. 2. The same as Fig. 1, but for the Fe II lines.


[FIGURE] Fig. 3. The heights of effective responses depending on oscillator strengths and excitation potentials: a and b to the temperature variations for the central depths ([FORMULA]) and the equivalent widths([FORMULA]) of Fe I, c to the temperature ([FORMULA]), pressure ([FORMULA]), microturbulence variations ([FORMULA]) for the central depths of Fe I lines as compared with the average heights of formation of the central depths ([FORMULA]).


[FIGURE] Fig. 4. The same as Fig. 3, but for the Fe II lines.

Tables 1 and 2, which are only available in electronic form, present the list of 604 Fe I and 58 Fe II lines using in this paper and data: 1) the atomic line parameters - the wavelength [FORMULA] (nm), the lower excitation potential EP (eV), the oscillator strength [FORMULA] ; 2) the line characteristics - the observed central line depth R, the calculated equivalent width W (pm); 3) the sensitivity indicators to the temperature for the central line depths [FORMULA], for the line depths on half-width [FORMULA], and for the equivalent widths [FORMULA] ; 4) the average geometrical heights of localization of the effective response to the temperature variations for the central line depths, [FORMULA] (km), for the line depths on half-widths, [FORMULA] (km), and for the equivalent widths, [FORMULA] (km).

As can be seen from Figs. 1 and 2, the sensitivity to the temperature is higher (approximately 10 times) than to other atmospheric parameters. Analyzing in detail the sensitivity indicators obtained in the present paper and in the papers of Sheminova (1993, 1995) for iron lines as well as for spectral lines of other atoms, we have established that the most responsive to the temperature are the lines with excitation potentials from 0 to 2 eV, central line depths up to 0.35, and equivalent widths up to 3 pm. Relative variations of equivalent widths ([FORMULA]) of these lines are 25-35% when the temperature changes by 2%. Medium-strong lines of light atoms with [FORMULA] eV are highly responsive to the gas pressure. For them, [FORMULA] is as much as 25-48% when [FORMULA] changes by 30%. Strong lines of heavy atoms with [FORMULA] 8-12 pm are very sensitive to the microturbulent velocity. For these lines, [FORMULA] amounts to 11-18% when [FORMULA] changes by 50%.

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© European Southern Observatory (ESO) 1998

Online publication: December 8, 1997
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