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Luminous Blue Variable (LBV) stars are evolved massive objects, previous tocore-collapse supernova. LBVs are characterized by photometric andspectroscopic variability, produced by strong and dense winds, mass-loss eventsand very intense UV radiation. LBVs strongly disturb their surroundings byheating and shocking, and produce important amounts of dust. The study of thecircumstellar material is therefore crucial to understand how these massivestars evolve, and also to characterize their effects onto the interstellarmedium. The versatility of NIKA2 is a key in providing simultaneousobservations of both the stellar continuum and the extended, circumstellarcontribution. The NIKA2 frequencies (150 and 260 GHz) are in the range wherethermal dust and free-free emission compete, and hence NIKA2 has the capacityto provide key information about the spatial distribution of circumstellarionized gas, warm dust and nearby dark clouds; non-thermal emission is alsopossible even at these high frequencies. We show the results of the first NIKA2survey towards five LBVs. We detected emission from four stars, three of themimmersed in tenuous circumstellar material. The spectral indices show a complexdistribution and allowed us to separate and characterize different components.We also found nearby dark clouds, with spectral indices typical of thermalemission from dust. Spectral indices of the detected stars are negative andhard to be explained only by free-free processes. In one of the sources,G79.29+0.46, we also found a strong correlation of the 1mm and 2mm continuumemission with respect to nested molecular shells at 0.1 pc from the LBV. Thespectral index in this region clearly separates four components: the LBV star,a bubble characterized by free-free emission, and a shell interacting with anearby infrared dark cloud.

NIKA2 observations around LBV stars: emission from stars and circumstellar material