Modelling spectral line profiles of wind-wind shock emissions from massive binary systems

D. Falceta-Goncalves*, Z. Abraham, V. Jatenco-Pereira

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

10 Citations (Scopus)

Abstract

One of the most intriguing spectral features of Wolf-Rayet (WR) binary stars is the presence of time-dependent line profiles. Long-term observations of several systems revealed the periodicity of this variability, synchronized with the orbital movement. Several partially successful models have been proposed to reproduce the observed data. The most promising model assumes that the origin of the emission is the wind-wind interaction zone. In this scenario, two high velocity and dense winds produce a strong shock layer, responsible for most of the X-rays observed from these systems. As the gas cools down, flowing along the interaction surface, it reaches recombination temperatures and generates the emission lines. Luhrs noted that, as the secondary star moves along its orbital path, the shock region, of conical shape, changes its position with relation to the line of sight. As a consequence, the stream-measured Doppler shift presents time variations resulting in position changes of the spectral line. However, his model requires a very thick contact layer and also fails to reproduce recently observed line profiles of several other WR binary systems. In our work, we present an alternative model, introducing turbulence in the shock layer to account for the line broadening and opacity effects for the asymetry in the line profiles. We showed that the gas turbulence avoids the need of an unnaturally large contact layer thickness to reproduce line broadening. Also, we demonstrated that if the post-shock gas is optically thick at the observed line frequency, the emission from the opposing cone surface is absorbed, resulting in a single-peaked profile. This result fully satisfies the recent data obtained from massive binary systems, and can help in the determination of both the winds and the orbital parameters. We successfully applied this model to the Br22 system and determined its orbital parameters.

Original languageEnglish
Pages (from-to)1295-1300
Number of pages6
JournalMonthly Notices of the Royal Astronomical Society
Volume371
Issue number3
DOIs
Publication statusPublished - 21 Sept 2006

Keywords

  • binaries : general
  • stars : winds, outflow
  • stars : Wolf-Rayet
  • WOLF-RAYET STARS
  • COLLIDING WINDS
  • RADIO-EMISSION
  • X-RAY
  • INHOMOGENEITIES
  • PERIASTRON
  • COLLISION
  • HD-152270
  • WR-79

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