Z Cha in superoutburst: periodic variation in the systemic velocity

• Published in: Monthly notices of the Royal Astronomical Society 1988-03, Vol.231 (1), p.1-24
• Main Authors: Honey, W. B., Charles, P. A., Whitehurst, R., Barrett, P. E., Smale, A. P.
• Format: Article
• Language: English
• Subjects: Astronomy; Earth, ocean, space; Exact sciences and technology; Stars; Unusual and peculiar variables; Variable and peculiar stars (including novae)
• ISSN: 0035-8711; 1365-2966
• DOI: 10.1093/mnras/231.1.1

We present photometric and spectroscopic data from the May 1984 and December 1985 superoutbursts of the SU UMa system Z Cha. By fitting composite absorption and emission profiles to the spectroscopic data, radial velocity curves were produced for each night using Hβ, Hγ, Hδ, He Iλ4471, and Ca II K. The mean (γ) of each of these velocity curves is found to be non-zero (i.e. they do not represent the quiescent value of the systemic velocity) and it is found that γ is modulated on the superhump beat period of 2.1 days with a zero-velocity phase of ∼0.75, and amplitude of ∼80km s−1. The mean of the modulation is compatible with the quiescent value of γ=0±9 km s−1. This observational result is interpreted with new non-axisymmetric disc simulations as arising in an eccentric, precessing disc which is tidally distorted by the secondary.