Origin and possible birthplace of the extreme runaway star HIP 60350

Abstract

Using the recently determined spatial velocity components of the extreme runaway star HIP 60350 and a gravitation potential model of the Galaxy, we integrate the orbit of HIP 60350 back to the plane of the Galaxy. In this way, a possible location of the formation of the star is determined. We estimate the uncertainty of the result due to the uncertainties of the gravitational potential model and the errors in the spatial velocity components. The place of birth lies (within the errors) near the position of the open cluster NGC 3603. However, the ejection event which occured about 20 Myr ago is in contradiction with the cluster mean age of 3-4 Myr. We suggest that it occured at an earlier phase in sequential star formation in that region. We discuss also ejection mechanisms. Due to the rather high mass of the star (about 5 \Msol), the most probable model is that of dynamical ejection.Comment: Astron. Astrophys. submitted, 7 pages, 5 eps figure