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Description
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 (T_1_=6350K). The masses and radii (M_1_=0.96+/-0.02, M_2_=0.84+/-0.01M_{sun}_, R_1_=1.39+/-0.01, R_2_=0.98+/-0.01R_{sun}_) reveal that both stars have already slightly evolved away from the main-sequence band, having an age of about 7Gyr, 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+/-2km/s, while its distance, computed from orbital parameters and the derived reddening E_B-V_=0.053, is 496+/-35pc. 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.
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