The GALAH survey: Unresolved triple Sun-like stars discovered by the Gaia mission

Research output: Contribution to journalArticle


The latest Gaia data release enables us to accurately identify stars that are more luminous than would be expected on the basis of their spectral type and distance. During an investigation of the 329 best solar twin candidates uncovered among the spectra acquired by the GALAH survey, we identified 64 such overluminous stars. In order to investigate their exact composition, we developed a data-driven methodology that can generate a synthetic photometric signature and spectrum of a single star. By combining multiple such synthetic stars into an unresolved binary or triple system and comparing the results to the actual photometric and spectroscopic observations, we uncovered 6 definitive triple stellar system candidates and an additional 14 potential candidates whose combined spectrum mimics the solar spectrum. Considering the volume correction factor for a magnitude-limited survey, the fraction of probable unresolved triple stars with long orbital periods is ~2 per cent. Possible orbital configurations of the candidates were investigated using the selection and observational limits. To validate the discovered multiplicity fraction, the same procedure was used to evaluate the multiplicity fraction of other stellar types.


  • Klemen Čotar
  • Tomaž Zwitter
  • Gregor Traven
  • Janez Kos
  • Martin Asplund
  • Joss Bland-Hawthorn
  • Sven Buder
  • Valentina D'Orazi
  • Gayandhi M. De Silva
  • Jane Lin
  • Sarah L. Martell
  • Sanjib Sharma
  • Jeffrey D. Simpson
  • Daniel B. Zucker
  • Jonathan Horner
  • Geraint F. Lewis
  • Thomas Nordlander
  • Yuan Sen Ting
  • Rob A. Wittenmyer
External organisations
  • University of Ljubljana
  • Australian National University
  • University of Sydney
  • University of California, Berkeley
  • Max Planck Institute for Astronomy
  • INAF - Osservatorio Astronomico di Padova
  • Macquarie University, Sydney
  • University of New South Wales
  • University of Southern Queensland
  • Carnegie Observatories
  • Princeton University
Research areas and keywords

Subject classification (UKÄ) – MANDATORY

  • Astronomy, Astrophysics and Cosmology


  • Binaries: general, Galaxy: stellar content, Methods: data analysis, Stars: solar-type
Original languageEnglish
Pages (from-to)2474-2490
Number of pages17
JournalMonthly Notices of the Royal Astronomical Society
Issue number2
Publication statusPublished - 2019
Publication categoryResearch