Title: Long-Term Light Curve of Highly-Variable Protostellar Star GM Cep Show Chinese title

Title: 高度变化的原恒星星GM Cep的长期光变曲线

Abstract: We present data from the archival plates at Harvard College Observatory and Sonneberg Observatory showing the field of the solar type pre-main sequence star GM Cep. A total of 186 magnitudes of GM Cep have been measured on these archival plates, with 176 in blue sensitivity, 6 in visible, and 4 in red. We combine our data with data from the literature and from the American Association of Variable Star Observers to depict the long-term light curves of GM Cep in both B and V wavelengths. The light curves span from 1895 until now, with two densely sampled regions (1935 to 1945 in B band, and 2006 until now in V band). The long-term light curves do not show any fast rise behavior as predicted by an accretion mechanism. Both the light curves and the magnitude histograms confirm the conclusion that the light curves are dominated by dips (possibly from extinction) superposed on some quiescence state, instead of outbursts caused by accretion flares.Our result excludes the possibility of GM Cep being a FUor, EXor, or McNeil's Nebula type star. Several special cases of T Tauri stars were checked, but none of these light curves are compatible with that of GM Cep. The lack of periodicity in the light curve excludes the possibility of GM Cep being a KH 15D system. Show Chinese abstract

Abstract: 我们展示了来自哈佛大学天文台和索内贝格天文台档案底片的数据，显示了太阳型前主序星GM Cep所在的天区。在这批档案底片上总共测量了186个GM Cep的星等，其中176个在蓝敏波段，6个在可见光波段，4个在红敏波段。我们将我们的数据与文献中的数据以及美国变星观测协会的数据相结合，描绘出GM Cep在B和V波长上的长期光变曲线。这些光变曲线的时间跨度从1895年至今，有两个密集采样的区域（B波段的1935年至1945年，以及V波段的2006年至今）。长期光变曲线并未显示出吸积机制预测的快速上升行为。光变曲线和星等直方图均证实，光变曲线主要由一些可能源于消光的“凹陷”叠加在一个平静状态之上，而不是由吸积耀斑引起的爆发。我们的结果排除了GM Cep是FUor、EXor或McNeil星云型恒星的可能性。检查了几种特殊类型的T Tauri星，但它们的光变曲线都不符合GM Cep的特征。光变曲线中缺乏周期性排除了GM Cep是KH 15D系统的可能性。