All Figures

Figure 1: Acoustic oscillations of the star  Hor. The radial velocity curves obtained during the eight nights are displayed on this graph. For clarity they are arbitrarily shifted upwards by 10 m s-1 for each night. While the first and the four last nights are complete, the second, third, and fourth ones were partially cloudy, so only parts of them could be exploited. In this figure, the radial velocities have been corrected for long term variability due to stellar activity. The 6-min oscillations can be seen in the time series.

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In the text

	Figure 2: Frequency spectrum of the star  Hor. This spectrum is the Fourier transform of the radial velocity curves. The peaks at low frequencies are signatures of the stellar activity, while those above 2 mHz correspond to the acoustic frequencies.
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In the text

	Figure 3: Observed and computed echelle diagrams. The echelle diagram displays the frequencies of the oscillating modes on ordinates, and the same frequencies modulo the large separation on abscissas. The symbols correspond to the identified modes (aliases have been taken off), and the continuous lines correspond to one of our best models (the third one of those presented in Table 2).
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In the text

Figure 4: In the  plane, the three spectroscopic boxes presented in Table 1 are displayed: Santos et al. (2004) (box [Fe/H]=0.26); Gonzalez et al. (2001) (box [Fe/H]=0.19); Fischer & Valenti 2005 (box [Fe/H]=0.11). The open symbols correspond to the nine models which fit both the large and small separations. They correspond to three metallicities: [Fe/H]=0.11, 0.14, and 0.19 and three helium values: Y proportional to Z, Y=0.271, and Y=0.255. As discussed in the text, no model can be computed for the metallicity [Fe/H]=0.26, as the corresponding box lies below the ZAMS. Inside a metallicity group (same symbols), the model with the highest Y value is on the left, the one with the lowest Y value on the right.

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In the text