MWC 560 (V694 Mon) is classified as a symbiotic binary consisting of a white dwarf and an M5III red giant. In this object, a very- high-speed component, thought to be a jet, has been reported in the hydrogen Balmer line. We have been conducting long-term spectroscopic monitoring since the brightening in 2016 February. An irregular rebrightening was reported by Goranskij et al. (2018, Astronomer’s Telegram, 12227), who also showed that the high-velocity absorption component was not seen on 2018 November 16. Our low-resolution spectroscopic observations showed no high-velocity absorption component on 2018 November 14, and wide emission lines in Balmer line region (Hα, Hβ). However, high-resolution spectroscopy revealed the presence of slow, weak absorbing components and an emission wing on 2018 December 25. MWC 560 began to brighten in 2018 November, and it is gradually brightening as of 2020 April 14. For the absorption component, we propose a shell expansion of a classical symbiotic nova that occurred in 2016. During the 2018 brightening a new emission wing with vFWHM ≈ 700 km s−1 was confirmed, which could be triggered by disk instability like a dwarf nova. This paper summarizes the results of long-term monitoring observations and the recent changes in MWC 560.

中文翻译：

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共生星MWC 560 2018意外增亮前后的光谱监测

MWC 560 (V694 Mon) 被归类为由一颗白矮星和一颗 M5III 红巨星组成的共生双星。在这个天体中，一个被认为是喷气机的超高速部件已被报道在氢气 Balmer 线中。自 2016 年 2 月天亮以来，我们一直在进行长期的光谱监测。Goranskij 等人报道了不规则的再亮化。(2018, Astronomer's Telegram, 12227)，他还表明在 2018 年 11 月 16 日没有看到高速吸收分量。我们的低分辨率光谱观测显示在 2018 年 11 月 14 日没有高速吸收分量，并且在Balmer 线区域 (Hα, Hβ)。然而，高分辨率光谱显示在 2018 年 12 月 25 日存在缓慢、弱吸收的成分和发射翼。MWC 560 于 2018 年 11 月开始变亮，并且从 2020 年 4 月 14 日开始逐渐变亮。对于吸收成分，我们提出了 2016 年发生的经典共生新星的壳膨胀。在 2018 年增亮期间，确认了 vFWHM ≈ 700 km s-1 的新发射翼，这可能是由像矮新星这样的磁盘不稳定性触发的。本文总结了长期监测观测结果和MWC 560近期变化。