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Paper: A Monte Carlo Study of the Effects of Collisional De-excitation on the Resonance Doublet Flux Ratios in Symbiotic Stars
Volume: 404, The Eighth Pacific Rim Conference on Stellar Astrophysics: A Tribute to Kam Ching Leung
Page: 334
Authors: Kang E.H.; Lee H.W.
Abstract: Arising from S1/2 - P3/2, P1/2 transitions, the resonance doublet lines such as O VI 1032, 1038 and C IV 1548, 1551 are generated with the fixed ratio of 2:1, which is inconsistent with spectroscopic studies of many symbiotic stars from UV space telescopes. For an emission nebula with a size R ~ 1012 cm and an electron number density ne ~ 1010 cm-3, the collisional de-excitation time scale is tC ~ 10-3 s and line center optical depths for major resonance doublets are of order τ ~ 105, from which the probability pcoll of collisional de-excitation per scattering is ~ 10-5. Using a Monte Carlo technique, we investigate the collisional de-excitation effect and find that various line ratios are obtained in media with the product pcollτ0 of order unity. We provide a fit to the flux ratios using a linear function of pcoll τ0 when τ0 pcoll ~ 1.
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