Astrophysical laser operating in the OI 8446-Åline in the Weigelt blobs of η Carinae

Abstract

Within the framework of a simple model of photophysical processes in the Weigelt blobs in the vicinity of the luminous blue variable (LBV) star η Carinae, we explain the presence of the fluorescent <OI> 8446-Åand forbidden [OI] 6300-Ålines as well as the absence of the allowed OI 7774-Åline in spectra recorded with the Hubble Space Telescope (HST)/STIS instrument (Gull et al.). From atomic data and estimated stellar parameters we demonstrate that there is a population inversion and stimulated emission in the 3p³P-3s³S transition λ8446 due to photoexcitation by accidental resonance (PAR) by H Lyβ radiation.