All Figures

	Figure 1: alpha Ara flux measured by the VLTI/MIDI (8-13 m) instrument with ISO data (2.5-11.5 m) plotted as solid line compared with the theoretical SED of the star alone (dashed line) and the star+envelope emission (dotted line) assuming a distance of 105 pc. Note the IR excess starting around 5 m, i.e. log .
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In the text

	Figure 2: H and H line profiles observed in mid-1999 (solid lines) compared with the best SIMECA fits (dotted lines).
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In the text

Figure 3: a) Observed Pa line profile (mid-2003, solid line) compared to the modeled one based on the parameters determined by the fit of the 1999 H and H line profiles (dotted line). b) Observed Pa line profile (solid line) and the best fit from the SIMECA code (dotted line). To compensate for the effects of non-simultaneous observations, the density of the disk was allowed to vary in a small range. This fit has been obtained with a disk density lower by 25% compared to the best model based on 1999 H and H lines.

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In the text

	Figure 4: Variation of the H equivalent width ( EW) with time. The data were taken from Dachs et al. (1990): crosses; Hanuschik et al. (1995): stars and this work: diamond.
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In the text

	Figure 5: H line profile obtained in April 1999 with the HEROS instrument at la Silla (Chile) and the SIMECA fit (dotted line) for the base density used to fit the 2003 Pa profile. The strength of the line is comparable of the one reported in 1982 or 1987, for instance see Fig. 2 by Hanuschik et al. (1995).
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In the text

	Figure 6: VLTI/MIDI data for the 79 m ( left) and 102 m ( right) baselines and theoretical visibilities from SIMECA (dashed line) for the distance of 105 pc estimated from our SED fit (see Fig. 1). The error bars are equivalent to one sigma.
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In the text

	Figure 7: VLTI/MIDI data for the 79 m ( left) and 102 m ( right) baselines and theoretical visibilities from SIMECA (dashed line) for a truncated disk at 22  by a possible companion. The error bars are equivalent to one sigma.
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In the text

Figure 8: a) Theoretical visibilities for the H, H, Pa and Br lines for baseline orientations corresponding to the ones observed on June 16, i.e. PA = 7 onto the sky plane, for both scenarios discussed; b) model data for a disk with the parameters which fits the 2003 Pa line profile, but not in agreement with the VLTI/MIDI visibilities (Fig. 6). On the right side model data for a disk truncated at 22 , e.g. by a putative companion, is presented, being in agreement with the observed visibilities (Fig. 7).

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In the text

	Figure 9: Diagram of alpha Ara circumstellar envelope projected onto the sky plane (with arbitrary oblateness) based on polarization (P) measurements (PA = 172 ) obtained by McLean & Clarke (1979) and Yudin et al. (1998). The actually observed VLTI baseline positions are shown for June, 16: PA = 7 , B=102 m and June, 17: PA = 55 , B=79 m.
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In the text

	Figure 10: Variation of the height ratio of violet and red emission peaks of the H line during the H EROS observations 1999.
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In the text

	Figure 11: Radial velocity changes of the central depression of H during the H EROS observations 1999.
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In the text

	Figure 12: Average of the IUE-spectra of alpha Ara (dotted) compared to a theoretical spectrum with  K and (solid line).
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In the text

	Figure 13: Schematic view of the alpha Ara circumstellar environment as used in this work (see Table 4).
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In the text