Searching for variability and companions to brown dwarfs in NGTS

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.