MILLIMETER RECOMBINATION LINES TOWARDS ETA-CARINAE

We report the detection of the millimeter recombination lines H40 alph a, H30 alpha, H29 alpha, H50 beta and H37 beta towards Eta Carinae (et a Car). All the recombination lines show a similar line profile. A str ong narrow component is seen at a velocity of V-lsr similar to -50 kms (-1), significantly blue-shifted with respect to the systemic velocity of eta Car (-16 kms(-1)). Underlying this main component a very broad emission is also detected in the alpha lines, extending from similar to -200 to similar to 100 kms(-1). The profiles are markedly asymmetri cal in the sense of enhanced blue-shifted emission both in the narrow and the broad features. We argue that most of the red-shifted emission is absorbed by the optically thick, strong radio continuum of the ion ized stellar wind of eta Car and that the millimeter recombination lin es are affected by maser emission. This is supported by simple model c alculations for the radiation transfer of the line and continuum emiss ion in eta Car.