Physical Properties of WR 90 (HD 156385) Based on Spectroscopic Study
Bakuh Danang Setyo Budi (1,2), Hakim Luthfi Malasan (1,2,3,4*)

1) Department of Astronomy, Institut Teknologi Bandung, Jalan Ganesha 10, Bandung 40132, Indonesia
2) Bosscha Observatory, Institut Teknologi Bandung, Jalan Peneropongan Bintang, Bandung Barat 40391, Indonesia
3) Department of Atmospheric and Planetary Sciences, Institut Teknologi Sumatera, Lampung 35365, Indonesia
4) ITERA Astronomical Observatory (IAO), Institut Teknologi Sumatera, Lampung 35365, Indonesia
*Email: malasan[at]itb.ac.id

Abstract

Wolf-Rayet star is one of the astronomical objects that have an emission line on its spectrum that exhibits unusual abundance of helium, nitrogen,carbon, and oxygen elements when compared to the spectrum of other stars in general. In this work, observation of WR 90 (HD 156385) was conducted using a low-resolution spectrograph NEO-R1000 (\(R\sim\)1000) at GAO-ITB RTS (27.94 cm,F/10.0), Bosscha Observatory. Determination of stellar parameters has been implemented using two different methods: The first method derives an estimation of effective temperature and radius using the blackbody continuum model approximation, second method to estimates stellar temperature, radius, and luminosity using PoWR (The Postdam Wolf-Rayet) spectrum grid model. Furthermore, asymptotic terminal velocity was derived from the gaussian decomposition of optical spectrum emission line and the P-Cygni profile analysis of the high-resolution IUE UV spectrum, the mass loss rate of Wolf-Rayet star has been determined. The data used in both methods are low- and high-resolution ultraviolet spectra retrieved from IUE (International Ultraviolet Explorer) archival and optical spectrum of our observations. The obtained results are compared with observations that have been made before.

Keywords: Wolf-Rayet star, Physical Parameter, Blackbody Fitting, The Potsdam Wolf-Rayet Models (PoWR), Terminal Velocity, P-Cygni Analysis

Topic: EARTH, ATMOSPHERIC, AND SPACE SCIENCE