Dense, dusty, and asymmetric circumstellar environment around the extreme Galactic red supergiant NML Cyg

Supernova observations imply the presence of a dense and asymmetric circumstellar medium (CSM) around SN Type II progenitors, whereas the mass loss from these progenitors, red supergiants, is still rather poorly constrained. Using interferometric observations with NOEMA at 230 GHz, we characterise the mass, morphology, and kinematics of the dust and gas in the circumstellar environment of the extreme Galactic red supergiant (RSG) NML Cyg. Two strong continuum components amount to an estimated total dust mass of ∼0.002 solar masses not located at the stellar position and significantly beyond the scales on which dust is detected at optical-to-MIR wavelengths. The extent of the detected CO emission shows that the outflow is formed by a mass-loss rate of several 10^-4 solar masses per year and is not primarily shaped by extreme irradiation from the Cyg OB2 cluster. We detect, but do not resolve, previously unseen high-velocity components close to the star and we propose that some of the very complex circumstellar structure could be the imprint of a hitherto unknown binary companion.