Investigation of [KSF2015] 1381-19L, a WC9-type Star in the High-extinction Galactic Region

Abstract

We report on a multiwavelength study of the Wolf–Rayet star [KSF2015] 1381-19L, which is located in the solar metallicity region (Z = 0.014) of the Milky Way, strongly obscured by interstellar dust. We perform a detailed characterization of the stellar atmosphere by fitting the spectral emission lines observed in the optical and near-infrared (NIR) bands, using CMFGEN. The best-fitted spectroscopic model indicates a highly luminous (10^5.89 L _⊙) star with a large radius (15 R _⊙) and effective temperature, wind terminal velocity, and chemical composition similar to those of Galactic WC9-dusty (WC9d)-type stars. The atmospheric ionization structure shows coexisting ionization states of different elements, simultaneously affecting the opacity and thermal electron balance. Fitting of the spectral energy data reveals high interstellar optical extinction (A _V = 8.87), while the IR extinction is found to be comparatively lower ( AKs=0.98 ). We do not detect any excess emission at NIR wavelengths due to dust. Upon comparison of our results with the GENEVA single-star evolutionary models (Z = 0.014), we identify the best possible progenitors (a rotating star of 67 M _⊙ and a nonrotating star of 90 M _⊙).