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Projeto Observacional para 2017A - SO2017A-007
Autor: Augusto Damineli Neto
Título: Constraining the nature of the secondary star in eta Carinae
Resumo: The secondary star in eta Carinae binary has never been detected directly, not. Limits to its nature have been derived from X-rays and nebular emission. The detection of He II 4686 revealed fundamental properties of the wind-wind collision, the binary system orbit orientation, and shed light on the nature of the low excitation spectroscopic events. Observations at phases far from periastron confirm that this line is present along the entire cycle. At these phases, given the physical conditions and orbit parameters, it is believed that the emission cannot be produced solely by the wind-wind collision, and that the secondary might play a role in the emission. In this case, the He II 4686 line would be subject to radial velocity shifts, which were not possible to measure in previously spectra with S/N~400-600. Our goal is to obtain S/N~1000 from apastron (May 2017) up to the next periastron (Feb 2020) to test this hypothesis. We also plan to observe the He II 4686 reflected in the bipolar nebula around eta Car to constrain the 3D orientation of the binary system.