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Projeto Observacional para 2017A - OP2017A-030

Autor: Carlos Guerrero
Instituição: ON

Marcelo Borges Fernandes
Valeri Orlov

Título: Speckle Interferometry of Southern binary stars

Resumo: The prospect of high-precision parallaxes that will be possible with the Gaia satellite, dramatically changes the landscape of observational stellar astrophysics: If one considers the Hipparcos double stars that lie within 250 pc of the Solar system, a parallax determined by Gaia would (conservatively) yield an uncertainty well under 1% for all these objects. The Hipparcos binaries, even if they are more distant, are also important in terms of binary statistics. We have identified two distinct samples of binaries (thin and thick disk populations) from Hipparcos and the Geneva spectroscopic catalog on the basis of kinematics, location relative to the plane of the Galaxy, and metallicity. We propose a speckle survey of Southern Hipparcos visual doubles and spectroscopic binary stars identified by the Geneva-Copenhagen spectroscopic survey, using the 1.60-m and the Ixon U888 camera. These systems represent our best chance to take advantage of Gaia parallaxes for the purpose of stellar mass determinations. The work proposed here will create an all-sky, volume-limited, speckle archive for both samples, complementing and enhancing a similar effort done by us, using the 2.1-m telescope of the OAN-SPM in the Northern Hemisphere. Once accurate information is known about these stars, a comparative study between the two samples can be completed. This would include, e.g., the period distribution as a function of metallicity and the mass-ratio distribution as inferred from the photometry and projected separation distribution, and (eventually) correlation between period and eccentricity or other orbital parameters. These statistics are expected to be related to dynamical interactions at the time of star formation and in the post-formation environment, and could be quite different for thin and thick disk samples. If so, this could provide important information about the formation of these structures in the Galaxy.