HOGWARTs is a web tool for the retrieval of galaxies within LIGO/Virgo localisation regions (Salmon et al. 2019). The galaxies are ranked in order of probability of merger, calculated according to the method laid out by Arcavi et al. 2017. The back-end galaxy ranking algorithm is open source and can be found on Github.

The list of galaxies can be further refined based on visibility at a specific location and time and with a user-specified limiting magnitude.