Astron. Astrophys. 342, L13-L16 (1999)

3. Conclusion and discussion

We have used the most precise and updated model of the Sun-LIC interaction to calculate the Ly- absorption by the neutral gas in and around the heliosphere along the line-of-sight towards Sirius. We find that the neutralized solar wind from the heliosheath is mainly responsible for the absorption, and that the red side of the absorption line is very well fitted when adding this absorption to the normal interstellar absorption. In these conditions, there is no need to propose interstellar hot gas from a conductive interface to explain the red wing absorption, as BVL95 did in their analysis.

Using analogies with the solar case, we also show that the remaining missing absorption on the blue side could be explained in the same way by a "siriosphere", if Sirius is embedded in the neighboring cloud seen towards the star, if it has a stronger wind than the Sun, and if Sirius B does not completely ionize the hydrogen in and around the siriosphere. In this interpretation, there is no need for neutral H associated with a supersonic wind like that proposed by Bertin et al. (1995b).

We also point out that the model results show that heliospheric absorption cannot be neglected in any Ly- analysis, whatever the line-of-sight direction, if the interstellar absorption is relatively low (N(HI) cm^-2).

© European Southern Observatory (ESO) 1999

Online publication: December 22, 1998
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