Investigation of [KSF2015] 1381-19L, a WC9-type star in the high extinction Galactic region

TL;DR

This study characterizes the Wolf-Rayet star [KSF2015] 1381-19L in the Milky Way using multi-wavelength data, revealing its stellar parameters, high extinction, and potential progenitors, contributing to understanding massive star evolution.

Contribution

First detailed spectral and photometric analysis of [KSF2015] 1381-19L, combining optical, NIR, and SED fitting to determine its properties and evolutionary context.

Findings

Star is highly luminous with $10^{5.89}L_{ m \,sun}$

No near-IR dust emission detected

Progenitors likely rotating 67 M$_{\ m \,\odot}$ or non-rotating 90 M$_{\ m \,\odot}$ stars

Abstract

We report a multi-wavelength study of the Wolf Rayet (WR) star: [KSF2015] 1381-19L, which is located in the solar metallicity region (Z=0.014) of the Milky Way Galaxy, strongly obscured by the 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 ($10^{5.89}L_{\odot}$) star with a larger radius ($15\,R_{\odot}$) and effective temperature, wind terminal velocity, and chemical composition similar to that 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 (SED) reveals high interstellar optical extinction ($A_{V}=$ 8.87) while the IR extinction is found to be comparatively lower ($A_{K_{s}}=$ 0.98). We do not detect any excess emission at near-IR 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 $67\,M_{\odot}$ and a non-rotating star of $90\,M_{\odot}$).