1995A&A...297..168C

Using the SEST telescope we have mapped the λ 1.3-mm and 2.9-mm continuum emission around Eta Carinae (η Car), the peculiar star belonging to the open cluster Trumpler 16 in the Carina Nebula. The maps are dominated by a central source whose position coincides with η Car. Extended millimeter continuum emission is detected both at λ 1.3 and 2.9-mm. This emission traces the optically thin free-free emission from the gas ionized by the nearby massive luminous stars of Trumpler 16. In 1992, the flux densities of η Car were 15.8±1.9Jy at λ1.3-mm and 4.9±0.7Jy at 2.9-mm. From an analysis of the spectrum from the near-infrared to the decimeter radio range, we show that the millimeter emission of η 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 400K. The total luminosity is L_IR=5x10⁶L_☉. Based on the millimeter flux densities measured in 1992, we derive a mass-loss rate of ∼2.4x10^–3M_☉yr^–1. Measurements obtained during the time interval from 1991 to 1994 indicate strong flux density variations at both millimeter wavelengths. We suggest that these variations are related to episodic shell ejections leading to variations in the degree of ionization in the wind of η Car.