Poster Presentation

Raman-scattered Ne VII λ973 at 4881 Å in the symbiotic star V1016 Cygni

Jeong-Eun Heo (Sejong University)

We present high-resolution spectra of the symbiotic star V1016 Cygni obtained with the Bohyunsan Optical Echelle Spectrograph in 2003 and 2005, from which we find a broad emission feature at 4881 Å. We propose that this broad feature is formed from Raman scattering of Ne VII λ973 by atomic hydrogen. Thus far, the detection of Raman-scattered lines by atomic hydrogen is limited to O VI λλ1032, 1038 and He II λλ940, 972 and 1025. With the adoption of a centre wavelength 973.302 Å for Ne VII λ973 and considering an air refractive index nair = 1.000 279 348, the atomic line centre of the Raman-scattered Ne VII feature is determined to be 4880.53 Å. The total cross-section at the line centre of Ne VII λ973 is computed to be 2.62 × 10−22 cm2, with a branching ratio of 0.17. We perform Monte Carlo simulations to fit the Raman-scattered Ne VII λ973. Assuming that the Ne VII and He II emission regions share the same kinematics with respect to the neutral scattering region, we find that the Raman-scattered He II λ972 at 4850 Å and Ne VII λ973 at 4881 Å are excellently fitted. We also propose that the He II and Ne VII emission regions were stationary with respect to the H I region in 2003, but that they were receding from it with a velocity ∼20 km s−1 in 2005.