Spectroscopic Observations of Ten Galactic Wolf–Rayet Stars at Bosscha Observatory: Determination of Stellar Parameters and Mass-loss Rates

Abstract

We present optical spectra of 10 Galactic Wolf–Rayet (WR) stars that consist of five WN and five WC stars. The optical observation was conducted using a low-resolution spectrograph NEO-R1000 (λ/Δλ ∼ 1000) at GAO-ITB RTS (27.94 cm, F/10.0), Bosscha Observatory, Lembang. We implemented stellar atmosphere Postdam Wolf–Rayet (PoWR) grid modeling to derive stellar parameters. The normalized optical spectrum can be used to find the best model from the available PoWR grid, then we could derive stellar temperature and transformation radius. To derive luminosity, stellar radius and color excess, we conducted a Spectral Energy Distribution (SED) analysis with additional data on the near-ultraviolet spectrum from the International Ultraviolet Explorer (IUE) database, and UBV and 2MASS JHK broadband filter data. Additional analysis to derive asymptotic terminal wind velocity was conducted from the P-Cygni profile analysis of the high-resolution IUE ultraviolet spectrum. With previously derived parameters, we could determine the mass loss rate of the WR stars. Furthermore, we compared our results with previous work that used PoWR code and the differences are not more than 20%. We conclude that the PoWR spectral grid is sufficient to derive WR stellar parameters quickly and could provide more accurate initial parameter input to the PoWR program code.