Spectroscopy of helium dwarf novae in AM CVn systems

矮新星爆发被认为是CV系统中的盘状不稳定性，导致原生白矮星的质量吸积率增加。我们建议对AM-CVn双星系统中的三颗氦矮新星进行光谱观测。在AM CVn系统中的施主星是一颗富氦(半)简并星，因此，与其他CVs不同，吸积盘以氦为主。因此，突出行为有很大的不同。我们目标的爆发周期大约是几天。为了表征吸积盘的物理状态，我们想要研究作为位相函数的光谱可变性。光谱分析将使用非LTE吸积盘模型，该模型允许确定例如质量-吸积率和化学成分。

Dwarf nova outbursts are assumed to be disc instabilities in CV systems leading to enhanced mass-accretion rates onto the primary white dwarf. We propose to perform spectroscopic observations of three helium dwarf novae in AM CVn binary systems. The donor star in AM CVn systems is a helium-rich (semi-) degenerate star, hence, the accretion disc is dominated by helium in contrast to other CVs. Therefore the outburst behaviour is rather different. The outburst cycle times of our targets are of the order of days. We want to study the spectral variability as a function of phase in order to characterize the physical states of accretion discs. The spectra will be analysed with non-LTE accretion disc models, which allow to determine, e.g., mass-accretion rate and chemical composition.