Galactic LBV stars and their circumstellar material surveyed by NIKA2
Luminous Blue Variable (LBV) stars are evolved massive objects, previous to core-collapse supernova. LBVs are characterized by photometric and spectroscopic variability, produced by strong and dense winds, mass-loss events and very intense UV radiation. LBVs strongly disturb their surroundings by heating and shocking, and produce important amounts of dust. The study of the circumstellar material is therefore crucial to understand how these massive stars evolve, and also to characterize their effects onto the interstellar medium. The versatility of NIKA2 is a key in providing simultaneous observations of both the stellar continuum and the extended, circumstellar contribution. The frequencies surveyed (150 and 260 GHz) are in the range where thermal dust and free-free emission compete, and hence NIKA2 has the capacity to provide key information about the spatial distribution of both mechanisms. We show the results of the first NIKA2 survey in four fields towards five LBVs. Spectral indexes has a complex distribution without a clear dominance of an emission mechanism. At the stellar sources, there is a correlation of the spectral indexes with respect to the 1mm flux densities. In one of the sources, G79.29+0.46, we also found a strong correlation of the 1 and 2mm continuum emission with respect to nested molecular shells at 0.1 pc from the LBV.