Submillimetre variability of Eta Carinae: cool dust within the outer ejecta

Previous submillimetre (submm) observations detected 0.7M(circle dot) of cool dust emission around the luminous blue variable (LBV) star eta Carinae. These observations were hindered by the low declination of eta Carinae and contamination from free-free emission originating from the stellar wind. Here, we present deep submm observations with LABOCA at 870 mu m, taken shortly after a maximum in the 5.5-year radio cycle. We find a significant difference in the submm flux measured here compared with the previous measurement: the first indication of variability at submm wavelengths. A comparison of the submm structures with ionized emission features suggests the 870 mu m is dominated by emission from the ionized wind and not thermal emission from dust. We estimate 0.4 +/- 0.1 M(circle dot) of dust surrounding eta Carinae. The spatial distribution of the submm emission limits the mass loss to within the last thousand years, and is associated with mass ejected during the great eruptions and the pre-outburst LBV wind phase; we estimate that eta Carinae has ejected > 40 M(circle dot) of gas within this time-scale.