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Structure and Evolution of Stars Lecture 6 +23%45673+8%9: $ "# !. %&'()$;"...

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Structure and Evolution of Stars Lecture 6

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Logarithmic 1

Equivalent Width, log(W) [Ang]

10

.5 0 1216

1215

1

Square Root 1

.1

.5

Linear

0

1

1205 1210 1215 1220 1225

.01 .5 0 .001

1216

1215 .01

.1

1

10

2

10

3

10

4

10

5

10

Optical Depth at Line Core, log(!o)

6

10

7

10

8

10

bmicro (km s−1 )

log(A f λ)

growth of Fe I and Fe II lines, measured for one object (HD 95799) of our sample. Different symbols are used to represent three ranges of excitation potential, in this plot: their distribution shows that the excitation equilibrium is reached.

log (Wλ /λ)

Fe I lines

log (AFe gf λ)

Figure 1: Curve of growth of Fe lines for the star HD 95799. Different symbols indicate three ranges of excitation potential. The Fe II lines are represented by filled circles. The full line is a theoretical curve of growth. is the solar abundance of the element, gf the line transition probability of the line, and is a function of the element and of the stellar model.

The parameters [Fe/H] and v t are obtained by calculating a theoretical curve which gives the

Burris et al. 2000

Astron. Nachr. / AN (2010)

477

Fig. 1 Spectral comparison of stars in the main-sequence turn-off region with different metallicities. Several absorption lines are marked. The variations in line strength reflect the different metallicities. From top to bottom: Sun with [Fe/H] = 0.0, G66-30 with [Fe/H] = −1.6 (Norris et al. 1997c), G64-12 [Fe/H] = −3.2 (Frebel et al. 2005), and HE1327–2326 with [Fe/H] = −5.4 (Frebel et al. 2005).

Frebel 2010