Raman-Scattered O VI ll 6825 and 7088 and the Accretion Disk Emission Model in the Symbiotic Star V1016 Cygni

다국어 초록 (Multilingual Abstract)

We present a high-resolution spectrum of the symbiotic star V1016 Cygni obtained with the
Bohyunsan Optical Echelle Spectrograph. In this wide binary system of a hot white dwarf and a
Mira variable, some fraction of the slow stellar wind around the mass-losing giant may be captured
gravitationally by the white dwarf, giving rise to the formation of an accretion disk. We note that
the pro.les of the Raman scattered O VI ¸¸ 6825 and 7082 dier in such a way that the blue part
of the 7082 feature is relatively weaker than that of the 6825 feature. These scattered features are
formed via Raman scattering of O VI ¸¸ 1032 and 1038 near the giant where the neutral hydrogen
column density exceeds NHI ≫ 1022 cm¡2. The relative °ux de.cit in the blue part of the 7082
feature compared with that of the 6825 feature is interpreted as an indicator of the eccentric gas
°ows around the white dwarf. We argue that the O VI resonance doublet line ratio F1032=F1038
can be much smaller than the theoretically expected ratio of 2, depending on the closeness of the
O VI emission regions to the continuum emission region responsible for the photoionization. If the
accretion disk around the white dwarf is signi.cantly eccentric so that the red emission region is
located much closer to the white dwarf than the blue emission region, the O VI line ratio F1032=F1038
in the red emission region approches 1 whereas the line ratio remains close to 2 in the blue emission
region. Adopting this picture, we decompose the Raman scattered features into two components
that represent the continuum re°ection part and O VI pure emission part, which are characterized
by the °ux ratios 1 : 1 and 2 : 1, respectively.at