Accurate Orbital Solution for the New and Metal-poor Eclipsing Binary Tycho 5227-1023-1

Research output: Contribution to journalArticle


The orbit and physical parameters of the previously unsolved double-lined eclipsing binary Tyc 5227-1023-1, discovered during the search for RR Lyr variable candidate members of the Aquarius stream, are derived using high-resolution chelle spectroscopy and V, i' photometry. A synthetic spectral analysis of both components has been performed, yielding metallicity [M/H] =-0.63± 0.11 for both stars and a temperature for the secondary that is in close agreement with the one from the orbital solution, while the temperature of the primary is determined from photometry (T1 = 6350 K). The masses and radii (M1= 0.96 ± 0.02, M2 = 0.84 ± 0.01 M, R1 = 1.39 ± 0.01, R2 = 0.98 ± 0.01 R) reveal that both stars have already slightly evolved away from the main-sequence band, having an age of about 7 Gyr, and the results of the synthetic spectral analysis support the claim of corotation with the orbital motion. The radial velocity of the system is -60 ± 2 km s-1, while its distance, computed from orbital parameters and the derived reddening EB-V = 0.053, is 496± 35 pc. Even though Tyc 5227-1023-1 was initially treated as a possible member of the Aquarius stream, the results presented here disagree with reported values for this ancient structure and suggest a likely membership of the thick disk.


External organisations
  • University of Ljubljana
  • INAF - Osservatorio Astronomico di Padova
  • University of Padova
Research areas and keywords

Subject classification (UKÄ) – MANDATORY

  • Astronomy, Astrophysics and Cosmology


  • binaries: eclipsing, binaries: spectroscopic, Galaxy: disk, stars: fundamental parameters, stars: individual (Tycho 5227-1023-1)
Original languageEnglish
Article number52
JournalAstrophysical Journal
Issue number1
Publication statusPublished - 2017 Apr 10
Publication categoryResearch
Externally publishedYes