A Profile Analysis of Raman-scattered O VI Bands at 6825 Ã and 7082 Ã in Sanduleak's Star

Abstract

We present a detailed modeling of the two broad bands observed at 6825 Ã and 7082 Ã in Sanduleak's star, a controversial object in the Large Magellanic Cloud. These bands are known to originate from Raman-scattering of O VI $\hat{I}»\hat{I}»$ 1032 and 1038 photons with atomic hydrogen and are only observed in bona fide symbiotic stars. Our high-resolution spectrum obtained with the Magellan Inamori Kyocera Echelle (MIKE) spectrograph at the Magellan-Clay Telescope reveals, quite surprisingly, that the profiles of the two bands look very different: while the Raman 6825 Ã band shows a single broad profile with a redward extended bump, the Raman 7082 Ã band exhibits a distinct triple-peak profile. Our model suggests that the O VI emission nebula can be decomposed into a red, blue and central emission regions from an accretion disk, a bipolar outflow and a further compact, optically thick region. We also perform Monte Carlo simulations with the aim of fitting the observed flux ratio $F(6825)/F(7082)\sim 4.5$, which indicate that the neutral region in Sanduleak's star is characterized by the column density $N_{HI}\sim 1\times 10^{23}\mathrm{c}{\mathrm{m}}^{-2}$.

11 pages, 5 figures, accepted for publication in ApJ