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arXiv 1607.06309astro-ph.SR
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2016年独特的共生恒星MWC 560（= V694 Mon）的爆发，其长期的BVRI演化和显著的331天周期

The 2016 outburst of the unique symbiotic star MWC 560 (= V694 Mon), its long-term BVRI evolution and a marked 331 days periodicity

U. Munari, S. Dallaporta, F. Castellani, L. Baldinelli, G. L. Righetti, M. Graziani, G. Cherini, A. Maitan, S. Moretti, S. Tomaselli, A. Frigo

备注：
published in New Astronomy 49, 43 (2016)
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摘要：

在1990年的重大事件发生26年后，在2016年初，令人困惑的共生双星MWC 560进入了一个新的，甚至更明亮的爆发。我们介绍了我们对MWC 560的严格BVRI光度监测（分布在357个不同夜晚的451次独立运行），涵盖了2005-2016年的时间间隔，特别是当前的爆发。2016年爆发的一个显著特征是在最大亮度上升期间抑制了短期混沌变化，之后其振幅超过0.5 mag.类似于1990年的事件，当时该物体保持在最大亮度附近约6个月，当时太阳会合阻止了对当前爆发的进一步观测，MWC 560仍然在最大值附近，三个月后达到它。我们通过结合文献数据将我们的观测置于长期背景中，以提供完整的1928-2016年光变曲线。一些强周期性被发现调制MWC 560的光学光度。1860天的周期调节了BVR波段亮相的发生（1990年和2016年爆发之间正好有5.0个周期），而亮相期间达到的峰值亮度似乎以约9570天的周期变化。一个干净的331天周期调制I波段光变曲线，其中来自M巨星的发射占主导地位，光变曲线强烈地让人联想到椭球扭曲加上来自热伴星的辐射。1860天和331天作为系统轨道周期的利弊进行了审查，等待M巨星的光谱径向速度轨道来解决这个问题（假设轨道不是面向正面）。

英文摘要：

After 26 years from the major event of 1990, in early 2016 the puzzling symbiotic binary MWC 560 has gone into a new and even brighter outburst. We present our tight BVRI photometric monitoring of MWC 560 (451 independent runs distributed over 357 different nights), covering the 2005-2016 interval, and the current outburst in particoular. A stricking feature of the 2016 outburst has been the suppression of the short term chaotic variability during the rise toward maximum brightness, and its dominance afterward with an amplitude in excess of 0.5 mag. Similar to the 1990 event when the object remained around maximum brightness for ~6 months, at the time Solar conjunction prevented further observations of the current outburst, MWC 560 was still around maximum, three months past reaching it. We place our observations into a long term contex by combining with literature data to provide a complete 1928-2016 lightcurve. Some strong periodicities are found to modulate the optical photometry of MWC 560. A period of 1860 days regulate the occourence of bright phases at BVR bands (with exactly 5.0 cycles separating the 1990 and 2016 outbursts), while the peak brightness attained during bright phases seems to vary with a ~9570 days cycle. A clean 331 day periodicity modulate the I-band lightcurve, where the emission from the M giant dominates, with a lightcurve strongly reminiscent of an ellipsoidal distortion plus irradiation from the hot companion. Pros and cons of 1860 and 331 days as the system orbital period are reviewed, waiting for a spectroscopic radial velocity orbit of the M giant to settle the question (provided the orbit is not oriented face-on).

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