Constraining the orbital orientation of eta Carinae from H Paschen lines

Autor(es)

Falceta-Goncalves, D. ^[1] ; Abraham, Z. ^[2]

Afiliação do(s) autor(es)

^[1] Univ Cruzeiro Sul, Nucleo Astrofis Teor, BR-01506000 Sao Paulo - Brazil

^[2] Univ Sao Paulo, Inst Astron Geofis & Ciencias Atmosfer, BR-05508090 Sao Paulo - Brazil

• Tipo de documento: Artigo Científico
• Fonte: Monthly Notices of the Royal Astronomical Society; v. 399, n. 3, p. 1441-1446, NOV 1 2009.
• Citações Web of Science: 10

Resumo

During the past decade, several observational and theoretical works have provided evidence of the binary nature of eta Carinae. Nevertheless, there is still no direct determination of the orbital parameters, and the different current models give contradictory results. The orbit is, in general, assumed to coincide with the Homunculus equator although the observations are not conclusive. Among all systems, eta Car has the advantage that it is possible to observe both the direct emission of line transitions in the central source and its reflection by the Homunculus, which is dependent on the orbital inclination. In this work, we studied the orbital phase-dependent hydrogen Paschen spectra reflected by the south-east lobe of the Homunculus to constrain the orbital parameters of eta Car and determine its inclination with respect to the Homunculus axis. Assuming that the emission excess originates in the wind-wind shock region, we were able to model the latitude dependence of the spectral line profiles. For the first time, we were able to estimate the orbital inclination of eta Car with respect to the observer and to the Homunculus axis. The best fit occurs for an orbital inclination to the line of sight of i similar to 60 degrees +/- 10 degrees, and i{*} similar to 35 degrees +/- 10 degrees with respect to the Homunculus axis, indicating that the angular momenta of the central object and the orbit are not aligned. We were also able to fix the phase angle of conjunction as similar to -40 degrees, showing that periastron passage occurs shortly after conjunction. (AU)

• Processo FAPESP: 06/57824-1 - Aplicação de modelos teórico-computacionais em Astrofísica
• Beneficiário: Gustavo Amaral Lanfranchi
• Modalidade de apoio: Auxílio à Pesquisa - Jovens Pesquisadores