Analysing Hubble Space Telescope data for the detection of ultracool dwarf binaries.

Some large stellar-like objects reach their maximum mass before they become dense enough to ignite and begin fusing, leading them to join a group of objects known as brown dwarfs. Due to their size and temperature, low mass ultracool dwarfs (UCDs) are greatly underrepresented in observational studies [1]. As brown dwarfs don't display the same

characteristics as stars as they age the best way to determine properties, such as their mass, is through observations of binary systems. Binary dwarf systems, the result of two objects being gravitationally bound in orbit around a common centre of mass, are often overlooked largely due to the inherent difficulty of studying such systems. Many occasions

when these objects are catalogued and measured they are at large enough separations to be easily viewed as two distinct sources in the image, making analysis far easier [2]. For smaller separations however this process is not as straightforward, requiring more complex methods to resolve the two objects. As a result many of these possible binary systems have

not been studied to a satisfactory level. This project aims to return to archived Hubble Space Telescope data and apply modern post-processing techniques in order to detect and

catalogue previously undetected systems. Understanding these ultracool binaries is likely to provide key insight into the processes that dominated their formation and early lives. Brown dwarfs, especially UCDs, are effective analogues for high-mass exoplanets, sharing similar physical traits. Because of this,

understanding them could prove vital in further understanding their lower mass planetary counterparts going forward. The HST data will be analysed through the use of double Point Spread Function (PSF) fitting. As the light from a point source reaches the camera it refracts out, causing the object to effectively spread itself from the centre point. This spread can be accounted for by

understanding the optics well enough to create a PSF. By fitting this PSF to the spread point source, it can be reduced down and the origin of the source can be accurately determined. This technique has been proven as an effective means of binary analysis, as fitting two PSF to a frame can accurately determine the coordinates of both objects [3]. Applying this

method should allow us to detect those previously unnoticed binaries in existing images.