2017ApJ...839...52T

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 echelle 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 E_B–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.