Luminous Blue Variable stars as dust factories at sub-solar metallicities

Luminous Blue Variable stars (LBVs) are evolved massive stars that undergo instabilities and experience outbursts with very high mass-loss rates. An extreme example in our Galaxy is eta Carinae, that in the XIX century ejected up to 40 solar masses at rates higher than 10^{-1} Msun/ yr, of which about 0.2 Msun was in the form of dust. Several LBVs in our Galaxy present extended circumstellar nebulae, often with large masses of dust (usually about 10^{-2} Msun). How this dust is formed is not well understood, but the physical conditions in their ejecta during the giant eruptions seem favourable for the formation and growth of dust. For these reasons LBVs are candidate producers of dust in the early Universe and in starburst galaxies, where massive stars were more numerous than at present. This scenario is as-yet untested due to the paucity of suitable IR/sub-mm data of LBVs in sub- solar metallicity environments. We carried out a pilot study of LBVs in the Magellanic Clouds (MCs) with ALMA, VISIR and ATCA. We will show some results from this study, focusing on the discovery with ALMA Band 7 of a massive dusty nebula around LBV RMC143 in the Large Magellanic Cloud. We will also discuss future perspectives to evaluate the importance of LBVs to dust production in the MCs and in high-redshift galaxies.