Raman-scattered O VI λ6825 and the Accretion Disk Emission Model in the Symbiotic Stars V1016 Cygni and HM Sagittae
Abstract
We present the high-resolution spectra of the D-type symbiotic stars V1016 Cygni and HM Sagittae obtained with the Bohyunsan Optical Echelle Spectrograph (BOES) and investigate the double-peaked asymmetric profiles of the Raman scattered O VI λ6825 formed through Raman scattering of O VI λ1032 by atomic hydrogen. By adopting a wind accretion disk model, the O VI emission region is described by a Keplerian thin disk. The Raman scattering occurs in a neutral region near the giant, part of which is ionized by the strong UV radiation from the hot white dwarf. A Monte Carlo technique is used to compute the line profiles that are modulated by the slow spherical stellar wind from the giant component with the ionization front approximated by a hyperboloid. In order to account for the asymmetry and the central dip in the profiles, we add an O VI resonance scattering region between the hot white dwarf and the giant which hinders the incidence of slightly blue O VI photons upon the H I region. Overall good fits to the observed data are obtained from our model, which lends support to the accretion disk emission model. The best-fitting parameters for V1016 Cyg are vo=30 km s-1, v∞=11 km s-1, and vc=10 km s-1, where vo, v∞, and vc are the velocity of the outer disk rim, the terminal velocity of the giant wind, and the velocity component of the resonance scattering O VI region along the binary axis, respectively. Similar fitting parameters vo=26 km s-1, v∞=10 km s-1, and vc=7 km s-1 are obtained for HM Sge.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- November 2007
- DOI:
- 10.1086/521719
- arXiv:
- arXiv:0707.2978
- Bibcode:
- 2007ApJ...669.1156L
- Keywords:
-
- Accretion;
- Accretion Disks;
- Stars: Binaries: Symbiotic;
- Line: Profiles;
- Scattering;
- stars: individual (V1016 Cyg);
- stars: individual (HM Sge);
- Astrophysics
- E-Print:
- 11 pages, 9 figures, accepted for publication in ApJ