Searching for variability and companions to brown dwarfs in NGTS

褐矮星的形状与恒星类似，但大小与木星相当。这些不寻常的天体从未将氢融合成氦，所以一旦形成，它们就会简单地冷却和褪色。褐矮星的温度很低，这意味着它们的大气主要由水、甲烷和氨等分子组成。这些分子形成的云可以在褐矮星的旋转周期（大约几个小时）中看到变化，并在几周到几个月的时间内形成和消失。这些云是如何形成或分解的尚不清楚，但可以看到褐矮星的亮度，并随着时间的推移而变化。这被认为是由于褐矮星大气中的云层。12架下一代凌日巡天（NGTS）望远镜在智利全面投入使用，每天晚上监测数千颗恒星，寻找像海王星这样小的系外行星的证据。棕矮星在这些区域被观测到，然而，标准的数据简化管道只提取了最亮的恒星，而忽略了棕矮星和其他有趣的微弱物体，如晚期m矮星。为了观察褐矮星的光曲线，监测它们的云模式，并试图找到任何过境的同伴，我们需要一个管道来提取较暗物体的数据。每个NGTS场都有几个月的数据——允许大量数据进行分析。这些对棕矮星的长期观测将使我们开始了解棕矮星大气中云是如何随时间变化的。在这个博士项目中，我将首先开发一个深管道来研究来自NGTS的棕矮星和晚M矮星的光曲线。一旦这个管道投入使用，我将用它来搜索褐矮星的变异性，以及最冷的M矮星周围的变异性和系外行星。

rown dwarfs form like stars, but are the size of Jupiter. These unusual objects never fuse hydrogen into helium, and so once formed, they simply cool and fade. Brown dwarfs have low temperatures, which means they have atmospheres that are dominated by molecules such as water, methane, ammonia. These molecules form clouds which can be seen to change over the rotation period of the brown dwarf (which is around a few hours) and form and fade away over a period of a few weeks to a few months. How these clouds form or disintegrate is still unknown, but the brightness of the brown dwarfs can be seen and changes with time. This is believed to be due to the clouds in the atmosphere of the brown dwarfs.The twelve Next Generation Transit Survey (NGTS) telescopes are fully operational in Chile, monitoring thousands of stars every night for evidence of exoplanets as small as Neptune. Brown dwarfs are observed in these fields, however, the standard data reduction pipeline only extracts the brightest stars, missing the brown dwarfs, and other interesting faint objects, such as late M-dwarfs. In order to look at light curves of the brown dwarfs to monitor their cloud patterns, and attempt to find any transiting companions, we need a pipeline that will extract data for fainter objects. Months of data is available on each NGTS field - allowing for a lot of data to analyse. These long term observations of brown dwarfs will enable us to begin to understand how the clouds change with time in a brown dwarf atmosphere.In this PhD project I will first develop a deep pipeline to enable the study of light curves from brown dwarfs and late M dwarfs from NGTS. Once this pipeline is operational, I will use it to search for brown dwarf variability, as well as variability and exoplanets around the coolest M dwarfs.