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Paper: A Spectroscopic Study of Southern Binary Cepheids
Volume: 310, Variable Stars in the Local Group (IAU Colloquium 193)
Page: 403
Authors: Petterson, O.K.L.; Albrow, M.D.; Cottrell, P.L.; Fokin, A.
Abstract: High-resolution spectroscopic observations have been made of a number of southern binary Cepheids to determine their dynamical masses. The stars are part of a long-term program to observe southern variable starsf or which a valuable long-term database has been obtained. The most recent radial velocities have a precision of ~300 ms−1, allowing the detection of velocity differences of ~1 kms−1 with confidence. Masses were determined for three systems: the 9-day Cepheid S Mus (6.0±0.4 MSolar), the double-mode Cepheid Y Car (4.5±1.8 MSolar) and the 5-day Cepheid V350 Sgr (6.0±0.9 MSolar). For five Cepheids (YZ Car, AX Cir, V636 Sco, W Sgr and T Mon) new or improved orbital solutions were found. Line level effects have been observed in several species of lines. Most Cepheids were observed to show the same progression of line level effects. Using non-linear radiative hydrodynamical models, we have compared the results of these models with our observations. These have shown that AX Cir and YZ Car have the following properties: L = 2050 LSolar, M = 4.8 MSolar, Teff = 5900 K and L = 9350 LSolar, M = 7.7 MSolar, Teff = 5590 K. Our models show no strong shockwaves being produced. Good agreement was found between the observed and modelled spectral lines Fe I 5576Å, SiII 6347Å, BaII 5853Å and CaII 8542Å.
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