黄色共生星LT的第二次爆发
Second Outburst of the Yellow Symbiotic Star LT Delphini
摘要：
我们提出了我们的光电$UBV$观测黄色共生星LT Del在2010-2018年的结果。双星系统LT Del由一颗明亮的K巨星和一颗温度为$\sim$ 100 000 K的致密热星组成，轨道周期为476天。2017年，该变星经历了其研究历史上的第二次低振幅（$ΔV\sim 0.^{m}7$）爆发，其最大值发生在0.15 $\pm$ 0.05的轨道相位。发作持续时间为$\sim$ 60天。爆发中的$B-V$和$U-B$颜色明显变蓝。在1994年和2017年的爆发中，恒星的光度行为有所不同。在2017年爆发前的轨道周期中，$B$和$V$光变曲线中分别出现了深度为$0.^{m}15$和$0.^{m}20$的次极小值，并对其原因进行了讨论。介绍并解释了相位光和颜色曲线;解释了恒星在颜色-颜色图上的位置。我们已经估计了系统的冷，热组件的参数的基础上的距离确定从盖亚DR 2。
英文摘要：
We present the results of our photoelectric $UBV$ observations of the yellow symbiotic star LT Del over 2010-2018. The binary system LT Del, which consists of a bright K giant and a compact hot star with a temperature of $\sim$100 000 K, has an orbital period of 476 days. In 2017 the variable experienced a second low-amplitude ($ΔV\sim 0.^{m}7$) outburst in the history of its studies whose maximum occurred at an orbital phase of 0.15$\pm$0.05. The outburst duration was $\sim$60 days. The $B-V$ and $U-B$ colors in the outburst became noticeably bluer. A difference in the photometric behavior of the star in the 1994 and 2017 outburst has been detected. In the orbital cycle preceding the 2017 outburst a secondary minimum with a depth of $0.^{m}15$ and $0.^{m}20$ appeared in the $B$ and $V$ light curves, respectively, whose cause is discussed. The phase light and color curves are presented and explained; the position of the star on the color-color diagram is interpreted. We have estimated the parameters of the cool and hot components of the system based on the distance determination from Gaia DR2.
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