2004MNRAS.355..221J

We present our spectroscopic data around Hβ of the symbiotic star V1016 Cyg obtained with the Bohyunsan Echelle Spectrograph, in order to secure the broad emission feature at around λ 4850, which is formed through Raman scattering of Heiiλ 972. The total cross-section around Lyγ is given approximately by σ(λ) ≃ 1.7x10^–28[λ_Lyγ/(λ-λ_Lyγ)]² cm², with λ_Lyγbeing the line centre wavelength of Lyγ. We find a centre shift redward by an amount Δλ=+0.64 Å in the Raman scattered Heiiλ 4850. This redward centre shift is exactly analogous to the effect for the Raman scattered Heiiλ 6545 blueward of Hα discussed in our previous study. We compute the branching ratios of Raman scattering into the level 2s and levels 3s and 3d, which are subsequently incorporated in our Monte Carlo code. Using this code, we present the centre shift of the 4850 feature as a function of the neutral hydrogen column density in the scattering region. Assuming that Heiiλ 972 emission is characterized by a single Gaussian profile, the redward peak shift observed in the Raman scattered Heiiλ 4850 feature corresponds to the neutral column density N_Hi= 1.2x10²¹/cm2. Assuming that the covering factor ∼0.1 of the scattering region with respect to the Heii emission region and adopting a simple spherical stellar wind model, we may place an upper bound for the mass-loss rate of the giant component of V1016 Cyg. Our estimate can be severely affected by the kinematics of the scattering and Heii emission regions and the exact atomic physics, about which brief discussions are presented.