MILLIMETER EMISSION OF ETA-CARINAE AND ITS SURROUNDINGS

Using the SEST telescope we have mapped the lambda 1.3-mm and 2.9-mm c ontinuum emission around Eta Carinae (eta Car), the peculiar star belo nging to the open cluster Trumpler 16 in the Carina Nebula. The maps a re dominated by a central source whose position coincides with eta Car . Extended millimeter continuum emission is detected both at lambda 1. 3 and 2.9-mm. This emission traces the optically thin free-free emissi on from the gas ionized by the nearby massive luminous stars of Trumpl er 16. In 1992, the flux densities of eta Car were 15.8+/-1.9 Jy at la mbda 1.3-mm and 4.9+/-0.7Jy at 2.9-mm. From an analysis of the spectru m from the near-infrared to the decimeter radio range, we show that th e millimeter emission of eta Car is dominated by thermal emission from the ionized stellar wind. The infrared emission is dominated by dust radiation with temperatures ranging from 200 to 400 K. The total lumin osity is L(IR) = 5 10(6) L.. Based on the millimeter flux densities me asured in 1992, we derive a mass-loss rate of similar to 2.4 10(-3) M. yr(-1). Measurements obtained during the time interval from 1991 to 19 94 indicate strong flux density variations at both millimeter waveleng ths. We suggest that these variations are related to episodic shell ej ections leading to variations in the degree of ionization in the wind of eta Car.