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Investigations of stellar encounters in cluster environments have demonstrated their potential influence on the mass and angular momentum of protoplanetary discs around young stars. In this study it is investigated in how far the initial surface density in the disc surrounding a young star influences the outcome of an encounter. Based on a power-law ansatz for the surface density, $Sigma(r) propto r^{-p}$, a parameter study of star-disc encounters with different initial disc-mass distributions has been performed using N-body simulations. It is demonstrated that the shape of the disc-mass distribution has a significant impact on the quantity of the disc-mass and angular momentum losses in star-disc encounters. Most sensitive are the results where the outer parts of the disc are perturbed by high-mass stars. By contrast, disc-penetrating encounters lead more or less independently of the disc-mass distribution always to large losses. However, maximum losses are generally obtained for initially flat distributed disc material. Based on the parameter study a fit formula is derived, describing the relative mass and angular momentum loss dependent on the initial disc-mass distribution index p. Generally encounters lead to a steepening of the density profile of the disc. The resulting profiles can have a r^{-2}-dependence or even steeper independent of the initial distribution of the disc material. From observations the initial density distribution in discs remains unconstrained, so the here demonstrated strong dependence on the initial density distribution might require a revision of the effect of encounters in young stellar clusters. The steep surface density distributions induced by some encounters might be the prerequisite to form planetary systems similar to our own solar system.
Simulations of the collapse and fragmentation of turbulent molecular clouds and dense young clusters show that encounters between disc-surrounded stars are relatively common events which should significantly influence the resulting disc structure. In
The external destruction of protoplanetary discs in a clustered environment acts mainly due to two mechanisms: gravitational drag by stellar encounters and evaporation by strong stellar winds and radiation. If encounters play a role in disc destructi
We have performed a NLTE analysis of the infrared oxygen triplet for a large number of cepheid spectra obtained with the Hobby-Eberly telescope. These data were combined with our previous NLTE results for the stars observed with Max Planck Gesellscha
Observations indicate that the dispersal of protoplanetary discs in star clusters occurs on time scales of about 5 Myr. Several processes are thought to be responsible for this disc dispersal. Here we compare two of these processes: dynamical encount
Using 22 hydrodynamical simulated galaxies in a LCDM cosmological context we recover not only the observed baryonic Tully-Fisher relation, but also the observed mass discrepancy--acceleration relation, which reflects the distribution of the main comp