Published online by Cambridge University Press: 15 August 2009
A nonlinear radiative pulsating model for the long-periodic Cepheid l Carinae is presented. The LTE metallic lines and non-LTE hydroen lines are calculated and compared with the HARPS observations. We found that the weak and medium metallic lines well correspond to the radial Cepheid pulsation, while the Hα and some other strong lines reveal very strange behaviour which is not consistent with usual Cepheid pulsation. We conclude that l Car must have an extended circumstellar envelope, and discuss its possible parameters.