The kinematics of stars emerging from expanding shells: An analysis of theGould Belt

Using the available data for nearby stars from the Hipparcos catalog, we de rive the velocity ellipsoid of dwarf O-B5.5 stars belonging to the Gould Be lt (GB). The resulting vertex deviation for the whole sample of 252 stars i s l(nu) similar to -64 degrees +/- 20 degrees, and this value is modified t o l(nu) = 22 degrees +/- 8 degrees when the members of the Pleiades moving group are removed from the sample. This implies the existence of, at least, two different kinematic groups defining the GB system. We also model the e volution of a supershell in the solar neighborhood and obtain a fit to the shape and kinematics of the gas in the GB. Assuming that the expanding shel l is also forming stars, we obtain the corresponding velocity fields for th e shell and its newly formed stars. The average vertex deviation value resu lting from these models for the new stars (assuming different velocity disp ersion values and cutoff distances) is l(nu) similar or equal to 20 degrees and is consistent with the observed value when the Pleiades moving group m embers are excluded from the GB.