Extreme isolation of WN3/O3 stars and implications for their evolutionary origin as the elusive stripped binaries

Nathan Smith, Ylva Götberg, Selma E. de Mink

Research output: Contribution to journalArticlepeer-review

13 Scopus citations


Recent surveys of the Magellanic Clouds have revealed a subtype of Wolf-Rayet (WR) star with peculiar properties. WN3/O3 spectra exhibit both WR-like emission and O3 V-like absorption - but at lower luminosity than O3 V or WN stars. We examine the projected spatial distribution of WN3/O3 stars in the Large Magellanic Cloud as compared to O-type stars. Surprisingly, WN3/O3 stars are among the most isolated of all classes of massive stars; they have a distribution similar to red supergiants dominated by initial masses of 10-15M, and are far more dispersed than classical WR stars or luminous blue variables. Their lack of association with clusters of O-type stars suggests strongly that WN3/O3 stars are not the descendants of single massive stars (30M or above). Instead, they are likely products of interacting binaries at lower initial mass (10-18M). Comparison with binary models suggests a probable origin with primaries in this mass range that were stripped of their H envelopes through non-conservative mass transfer by a low-mass secondary. We show that model spectra and positions on the Hertzsprung-Russell diagram for binary-stripped stars are consistent with WN3/O3 stars. Monitoring radial velocities with high-resolution spectra can test for low-mass companions or runaway velocities.With lower initialmass and environments that avoid very massive stars, theWN3/O3 stars fit expectations for progenitors of Type Ib and possibly Type Ibn supernovae.

Original languageEnglish (US)
Article numberstx3181
Pages (from-to)772-782
Number of pages11
JournalMonthly Notices of the Royal Astronomical Society
Issue number1
StatePublished - Mar 21 2018


  • Stars: Wolf-Rayet
  • Stars: evolution
  • Stars: massive
  • Stars: winds
  • outflows

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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