Modeling stellar wind interaction with the ISM: Exploring astrospheres and their Lyman-α absorption

A numerical study of the interaction of a partially ionized interstellar medium with a stellar wind is presented. Of particular interest are the distributions of neutral hydrogen in the resulting astrospheres. We study is an element of Ind which has a higher relative velocity with respect to its local ISM than the Sun, and a solar-like stellar wind. A second study considers the astrosphere of a star with a niass-loss rate that is different from that of the Sun (gimel And). We calculate the additional absorption of the Ly-alpha lines of is an element of Ind and gimel And due to their respective astrospheric hydrogen walls and compare it with high-resolution UV spectra obtained by the Hubble Space Telescope (HST). Optimizing the fit between data and models leads to estimates of the otherwise elusive stellar wind parameters.