Abstract

Based on spectrophotometric observations, we have studied the variable activity of the symbiotic star CH Cyg from 2008 to 2018. The activity of the star was accompanied by a periodic increase of the flux in continuum and spectral lines. In the period of its activity, in both 2015 and 2018, absorption components appeared in the profiles of emission lines. The shape and radial velocity of the absorption components changed within a day. The maximum radial velocity of the absorption components was about \(-2000\) km s\({}^{-1}\). By modeling the observed spectral energy distribution, we have established that in the active state the luminosity and radius of the warm pseudo-photosphere of the symbiotic star increased by dozens of times, reaching \(L_{\textrm{WD}}=88.14L_{\odot}\) and \(R_{\textrm{WD}}=6.77R_{\odot}\), respectively, at maximum in 2018, and the source of activity of the symbiotic star is accretion onto a white dwarf from a red giant of spectral type M8III. The accretion rate at the maximum luminosity of the pseudo-photosphere has been estimated to be \(\dot{M}_{\textrm{acc}}\sim 4.7\times 10^{-8}M_{\odot}\) yr\({}^{-1}\). We have found a correlation between the TiO 6144 and 7125 molecular bands and the \(R\) brightness of the star, which suggests that a period of 750 days may be the pulsation period of the cool component, and, hence, we have concluded that the pulsations of the cool component at periastron or at a phase close to the periastron can provide an additional inflow of matter accreting onto the white dwarf. Thus, we have concluded that a variable mass accretion rate onto the white dwarf is responsible for the photometric variability of the symbiotic star. We show that 2015 and 2018 were the most active years for this star.

中文翻译：

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2008-2018年共生星CH Cyg活动的分光光度监测

摘要

基于分光光度观测，我们研究了共生星 CH Cyg 从 2008 年到 2018 年的可变活动。该恒星的活动伴随着连续谱和谱线通量的周期性增加。在其活动期间，在 2015 年和 2018 年，吸收成分出现在发射线的剖面中。吸收组件的形状和径向速度在一天内发生了变化。吸收分量的最大径向速度约为\(-2000\) km s \({}^{-1}\)。通过对观测到的光谱能量分布进行建模，我们确定在活动状态下，共生星暖伪光球的光度和半径增加了数十倍，达到\(L_{\textrm{WD}}=88.14L_{\odot}\)和\(R_{\textrm{WD}}=6.77R_{\odot}\)分别在 2018 年达到最大值，并且来源共生星的主要活动是从光谱类型为 M8III 的红巨星吸积到白矮星上。伪光球最大光度下的吸积率估计为\(\dot{M}_{\textrm{acc}}\sim 4.7\times 10^{-8}M_{\odot}\)年\({}^{-1}\)。我们发现 TiO 6144 和 7125 分子带与\(R\)恒星的亮度，这表明 750 天的周期可能是冷成分的脉动周期，因此，我们得出结论，冷成分在近星体或接近星体的阶段的脉动可以提供额外的物质流入白矮星。因此，我们得出结论，白矮星上可变的质量吸积率是造成共生星光度变化的原因。我们表明，2015 年和 2018 年是这颗恒星最活跃的年份。