Gemini/GNIRS infrared spectroscopy of the Wolf-Rayet stellar wind in Cygnus X-3

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Journal Title

Journal ISSN

Volume Title

A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä

Date

2017-12

Major/Subject

Mcode

Degree programme

Language

en

Pages

15
2181-2195

Series

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Volume 472, issue 2

Abstract

The microquasar Cygnus X-3 was observed several times with the Gemini North Infrared Spectrograph while the source was in the hard X-ray state. We describe the observed 1.0-2.4 mu m spectra as arising from the stellar wind of the companion star and suggest its classification as a WN 4-6 Wolf-Rayet star. We attribute the orbital variations of the emission line profiles to the variations in the ionization structure of the stellar wind caused by the intense X-ray emission from the compact object. The strong variability observed in the line profiles will affect the mass function determination. We are unable to reproduce earlier results, from which the mass function for the Wolf-Rayet star was derived. Instead, we suggest that the system parameters are difficult to obtain from the infrared spectra. We find that the near-infrared continuum and the line spectra can be represented with non-LTE Wolf-Rayet atmosphere models if taking into account the effects arising from the peculiar ionization structure of the stellarwind in an approximative manner. From the representative models we infer the properties of the Wolf-Rayet star and discuss possible mass ranges for the binary components.

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Keywords

Line: profiles, binaries: close, stars: winds, outflows, stars: individual: Cyg X-3, stars: Wolf-Rayet, infrared: stars, MASS BLACK-HOLE, X-RAY, CYG X-3, ORBITAL MODULATION, MODEL ATMOSPHERES, EMISSION-LINES, NGC 300, STARS, VARIABILITY, BINARY

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Citation

Koljonen , K I I & Maccarone , T J 2017 , ' Gemini/GNIRS infrared spectroscopy of the Wolf-Rayet stellar wind in Cygnus X-3 ' , Monthly Notices of the Royal Astronomical Society , vol. 472 , no. 2 , pp. 2181-2195 . https://doi.org/10.1093/mnras/stx2106