裸眼光学瞬变的频率极限从几分钟到几年
Frequency Limits on Naked-Eye Optical Transients Lasting from Minutes to Years
摘要：
有多少次明亮的光学瞬变发生在天空中，但没有报告？为了限制天文瞬变函数的亮端，使用Night Sky Live网络的全天空监视器进行了系统的搜索，以寻找变得足够明亮以被肉眼注意到的瞬变。两个鱼眼连续摄像机（CONCAMs）运行超过三年创建了一个数据库，搜索出现在时间连续的CCD帧的瞬态。虽然发现了单个候选瞬态（Nemiroff和Shamir 2006），但在此使用缺少更多瞬态来推断亮瞬态的一般频率的上限。要被探测到，瞬变必须增加超过三个视星等，才能在几分钟到几年的时间尺度上变得比视星等5.5更亮。得出的结论是，平均而言，少于0.0040（$t_{dur} / 60$秒）的瞬态持续时间$t_{dur}$之间的分钟和小时，发生在天空中的任何地方在任何一个时间。对于月到年的量级的瞬变，发生少于160（$t_{dur} / 1$年），而对于年到千年的量级的瞬变，发生少于50（$t_{dur}/1$年）$^2$。
英文摘要：
How often do bright optical transients occur on the sky but go unreported? To constrain the bright end of the astronomical transient function, a systematic search for transients that become bright enough to be noticed by the unaided eye was conducted using the all-sky monitors of the Night Sky Live network. Two fisheye continuous cameras (CONCAMs) operating over three years created a data base that was searched for transients that appeared in time-contiguous CCD frames. Although a single candidate transient was found (Nemiroff and Shamir 2006), the lack of more transients is used here to deduce upper limits to the general frequency of bright transients. To be detected, a transient must have increased by over three visual magnitudes to become brighter than visual magnitude 5.5 on the time scale of minutes to years. It is concluded that, on the average, fewer than 0.0040 ($t_{dur} / 60$ seconds) transients with duration $t_{dur}$ between minutes and hours, occur anywhere on the sky at any one time. For transients on the order of months to years, fewer than 160 ($t_{dur} / 1$ year) occur, while for transients on the order of years to millennia, fewer than 50 ($t_{dur}/1$ year)$^2$ occur.
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