EDP Sciences
Free access
Volume 508, Number 3, December IV 2009
Page(s) 1337 - 1341
Section Interstellar and circumstellar matter
DOI http://dx.doi.org/10.1051/0004-6361/200913250
Published online 04 November 2009
A&A 508, 1337-1341 (2009)
DOI: 10.1051/0004-6361/200913250

H$\alpha$ spectropolarimetry of the B[e] supergiant GG Carinae

A. Pereyra1, F. X. de Araújo1, A. M. Magalhães2, M. Borges Fernandes3, and A. Domiciano de Souza3

1  Observatório Nacional, Rua General José Cristino 77, São Cristovão, 20921-400, Rio de Janeiro, Brazil
    e-mail: pereyra@on.br
2  Departamento de Astronomia, IAG, Universidade de São Paulo, Rua do Matão 1226, São Paulo, SP, 05508-900, Brazil
3  UMR 6525 H. Fizeau, Univ. Nice Sophia Antipolis, CNRS, Observatoire de la Côte d'Azur, France

Received 4 September 2009 / Accepted 24 October 2009

Aims. We study the geometry of the circumstellar environment of the B[e] supergiant star GG Car.
Methods. We present observations acquired using the IAGPOL imaging polarimeter in combination with the Eucalyptus-IFU spectrograph to obtain spectropolarimetric measurements of GG Car across H$\alpha$ at two epochs. Polarization effects along the emission line are analysed using the Q-U diagram. In particular, the polarization position angle (PA) obtained using the line effect is able to constrain the symmetry axis of the disk/envelope.
Results. By analysing the fluxes, GG Car shows an increase in its double-peaked H$\alpha$ line emission relative to the continuum within the interval of our measurements (~43 days). The depolarization line effect around H$\alpha$ is evident in the Q-U diagram for both epochs, confirming that light from the system is intrinsically polarized. A rotation of the PA along H$\alpha$ is also observed, indicating a counter-clockwise rotating disk. The intrinsic PA calculated using the line effect (~85$\degr$) is consistent between our two epochs, suggesting a clearly defined symmetry axis of the disk.

Key words: polarization -- stars: individual: GG Car -- circumstellar matter

© ESO 2009