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@InProceedings{TeodoroDRMSRGMPWCPFGHHNAJCHGHG:2016:UnNaHe,
               author = "Teodoro, Mairan and Damineli, Augusto and Richardson, Noel and 
                         Moffat, Anthony F. J. and St-Jean, Lucas and Russel, Christopher 
                         Michael Post and Gull, Theodore R. and Madura, Thomas and Pollard, 
                         Karen and Walter, Frederick M. and Coimbra, Adriano and Prates, 
                         Rodrigo and Fern{\'a}ndez-Laj{\'u}s, Eduardo and Gamen, Roberto 
                         and Hickel, Gabriel and Henrique, William and Navarete, Felipe and 
                         Andrade, Thiago and Jablonski, Francisco Jos{\'e} and Corcoran, 
                         Michael F. and Hamaguchi, Kenji and Groh, Jose H. and Hillier, 
                         Desmond John and Gerd, Weigelt",
          affiliation = "USRA and {Universidade de S{\~a}o Paulo (USP)} and 
                         {Universit{\'e} de Montr{\'e}al} and {Universit{\'e} de 
                         Montr{\'e}al} and {Universit{\'e} de Montr{\'e}al} and 
                         NASA/GSFC and NASA/GSFC and USRA and {University of Canterbury} 
                         and {Stony Brook University} and LNA and LNA and {Universidad 
                         Nacional de La Plata} and {Universidad Nacional de La Plata} and 
                         {Universidade Federal de Itajub{\'a} (UNIFEI)} and {Universidade 
                         Federal de Itajub{\'a} (UNIFEI)} and {Universidade de S{\~a}o 
                         Paulo (USP)} and {Universidade de S{\~a}o Paulo (USP)} and 
                         {Instituto Nacional de Pesquisas Espaciais (INPE)} and USRA and 
                         CRESST and {Geneva Observatory} and {University of Pittsburgh} and 
                         {Max-Planck-Institut f{\"u}r Radioastronomie}",
                title = "Unveiling the nature of the He II \λ4686 periodic minima in 
                         \η Carinae",
                 year = "2016",
         organization = "American Astronautical Society, Meeting, 227.",
             abstract = "\η Carinae is known to be a massive binary system, but some 
                         of the orbital parameters remain uncertain. The nature of the 
                         periodic minima seen in several spectral features are associated 
                         with periastron passages near stellar conjunction, but its nature 
                         has been interpreted either as a low excitation event or as an 
                         eclipse of the hotter secondary star by the dense inner wind of 
                         the primary. We conducted an intense spectroscopic monitoring of 
                         the He II \λ4686 emission line across the 2014.6 event using 
                         ground- and space-based telescopes. Comparison with results from 
                         the past two events confirmed the stability of the equivalent 
                         width and radial velocity of this line, as well as the strict 
                         periodicity of its minima. In combination with different other 
                         measurements, the orbital period is 2022.7 (0.3) d. We adopted a 
                         power law model in combination with the total opacity in the line 
                         of sight to the apex of the wind-wind collision region obtained 
                         from hydrodynamic simulations to reproduce the observed He II 
                         \λ4686 equivalent width curve. We constrained the orbital 
                         inclination to 135153 and the longitude of periastron to 
                         234252. Periastron passage occurred on T (2014.6)=2456874.4 
                         (1.3) d. With these orbital elements, we successfully reproduced 
                         both the equivalent width curve observed from our direct view of 
                         the central source and the polar view. This suggests that the He 
                         II \λ4686 minimum is ultimately caused by an increase in the 
                         opacity in the line of sight to the emitting region as the 
                         secondary star moves behind the primary star and plunges into 
                         denser regions of its wind.",
  conference-location = "Kissimmee, FL",
      conference-year = "4-8 Jan.",
           targetfile = "Teodoro_unveiling.pdf",
        urlaccessdate = "26 nov. 2020"
}


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